Atoms and Molecules
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1. The chemical formula C6H12O6 contains much information. However, what information is NOT provided by the formula?
A. The number of atoms in a molecule
B. The name of the substance
C. The elements that make up the substance
D. Whether the substance is covalent or ionic
Answer is B: The name may be guessed at, but it is possible for two substances to have the same formula but a different structure. Glucose and fructose both have this formula.
2. Which of the particles listed below is the smallest?
A. An atom
B. A proton
C. An ion
D. A molecule
Answer is B: A proton is a sub-atomic particle so is smaller than all of the others
3. The chemical for sodium is which of the following?
A. Na
B. So
C. K
D. Si
Answer is A: Na is short for natrium which is the Latin name for sodium.
4. A molecular compound may be defined by which of the following?
A. Atoms from non-metal elements covalently bonded
B. Atoms from metal elements covalently bonded
C. Atoms from metal elements and non-metal elements covalently bonded
D. Atoms from non-metal elements ironically bonded
Answer is A: Only non-metal elements are involved in covalent (molecular) bonding.
5. Many drugs are neutralised to form salts and administered in this form. What is the main advantage of administering the salt form of the drug? It is usually:
A. Less toxic
B. More soluble in water
C. More pleasant to taste
D. More soluble in lipid
Answer is B: Salts, having particles that are electrically charged, are more likely to be soluble in water.
6. Which one of the following is INCORRECT?
A. Metal atoms will form compounds with non-metal atoms.
B. Metal atoms will form compounds with metal atoms.
C. Non-metal atoms will form compounds with non-metal atoms.
D. Metal atoms will not form compounds with metal atoms.
Answer is B: Metal atoms can only form (ionic non-molecular) compounds with non-metal atoms.
7. Choose the correct statement about hydrogen bonds.
A. They are more potent than covalent bonds.
B. They act between the H in one –OH or –NH group, and the O or N in another.
C. They operate within molecules.
D. They act between the H in one –OH or –NH group, and the H in another.
Answer is B: The slightly positive H atom in one molecule is attracted to the adjacent slightly negative O (or N).
8. Given that the atomic mass of nitrogen is 14 and of hydrogen is 1, what is the mass in grams of 1 mol of ammonia (NH3)?
A. 15
B. 16
C. 17
D. 18
Answer is C: From the formula, there is one N and three H atoms. So (1 × 14) + (3 × 1) = 17.
9. Choose the ending that will correctly complete the sentence: When atoms of a metal element and atoms of a non-metal element react, the result is:
A. A covalent compound consisting of molecules
B. A covalent compound consisting of ions
C. An ionic compound consisting of ions in a lattice
D. An ionic compound consisting of molecules in a lattice
Answer is C: Atoms of a metal element react with atoms of a non-metal element to form an ionic compound (ions held within a lattice when in solid form).
10. In a water molecule, the bond between oxygen (O) and hydrogen (H) is:
A. A covalent bond and a polar bond
B. An ionic bond
C. A covalent bond
D. An ionic bond forms an electrolyte
Answer is A: As both atoms are non-metals, the bonding is covalent. As the atoms differ in their attraction for the bonding electrons, the bond is polar (the electrons are more closely attracted to O).
11. Some atoms of potassium, K, contain 19 protons and 20 neutrons in their nuclei. What is the correct symbol for these atoms?
A. 1939K
B. 2019K
C. 1939K
D. 3920K
Answer is C: The number of protons (the atomic number) is written as a subscript. The sum of the number of protons and neutrons (the mass number) is written as a superscript.
12. Chemical elements can be divided into metal elements and non-metal elements. Which of the statements about metals and non-metals is correct?
A. Metals lose electrons to become charged particles called cations.
B. Most of the elements are non-metals.
C. Non-metals are located on the left-hand side of the periodic table.
D. Metals have low melting points and are good conductors of heat.
Answer is A: Metal ions are positively charged (having lost an electron/s), consequently they are attracted to a cathode (a negatively charged electrode).
13. Twenty-four of the chemical elements are essential to the human body. Four bulk elements, seven are macrominerals and 13 are trace elements. Which are the four bulk elements?
A. Calcium, carbon, hydrogen and oxygen
B. Nitrogen, carbon, hydrogen and oxygen
C. Calcium, nitrogen, carbon and oxygen
D. Carbon, oxygen, phosphorus and iron
Answer is B: These elements make up the bulk of proteins, carbohydrates and lipids.
14. Most non-molecular compounds are formed by the chemical combination of:
A. Molecules with molecules
B. Non-metals with non-metals
C. Metals with metals
D. Metals with non-metals
Answer is D: Ionic compounds are formed when metal atoms react with non-metal atoms. The structures they form are not molecular.
15. Molecules are relatively easy to separate from one another. This means that the bonds between them are:
A. Ionic
B. Covalent
C. Relatively weak
D. Relatively strong
Answer is C: Ease of separation implies relatively weak bonds. Both ionic and covalent bonds are strong.
16. What happens when a sodium atom reacts to form a compound? The atom will:
A. Gain one electron
B. Lose one electron
C. Gain two electrons
D. Lose two electrons
Answer is B: Sodium is a metal so will lose an electron. As it occurs in period IA of the periodic table, we know it loses a single electron.
17. When nitrogen combines with hydrogen to form a compound, its formula will be:
A. NH3
B. N3H
C. NH4
D. NH
Answer is A: N requires three electrons to complete its outer shell (it occurs in column VA of the periodic table), while H requires one. Hence three H must attach to a single N.
18. Which of the following type of bond between atoms is the weakest?
A. Ionic bond
B. Polar bond
C. Covalent bond
D. Hydrogen bond
Answer is D: The hydrogen bond is the weakest. Almost all covalent bonds are polar bonds.
19. Ionic, non-molecular compounds are likely to have which of the following sets of properties?
A. High melting point, often soluble in organic liquids, in pure form does not conduct electricity.
B. Low melting point, no strong odour, soluble in water, electrical conductivity in a solution.
C. High melting point, electrical conductivity in solution, no strong odour, often soluble in water.
D. Low melting point, strong odour, soluble in organic liquids, in pure form, do not conduct electricity.
Answer is C: High melting points and electrical conductivity are indicative of ionic compounds.
20. Which of the following best describes a molecule?
A. The simplest structure in an ionic compound
B. One-thousandth of a mole
C. The particles of which covalent compounds are composed
D. The smallest particle of an element
Answer is C: Molecules are the particles of covalent compounds.
21. Which of the following is true of metal elements?
A. The four most common metal elements in the body have the symbols: C, H,O and N.
B. They form compounds with non-metals.
C. When they form compounds, they gain electrons.
D. In the body, ions of metal atoms have a negative charge.
Answer is B: All other choices are wrong.
22. Which of the following symbols represents a chemical element?
A. O
B. CO
C. CO2
D. H3O+
Answer is A: O symbolises oxygen, element number 16.
23. What is the name given to the particles that make up a covalent compound?
A. Ions
B. Molecules
C. Anions and cations
D. Metal atoms
Answer is B: This is a definition of molecules.
24. Compounds may be described by which of the following sentences?
A. Pure substances that contain two or more elements.
B. Materials that are composed of particles called molecules.
C. Materials composed of more than one part, and the parts may be present in any proportion.
D. Substances that appear on the right-hand side of the periodic table.
Answer is A: Choice B refers only to covalent compounds.
25. The symbol for potassium is which of the following?
A. PO4
B. Po
C. P
D. K
Answer is B: K is from kalium which is the Latin word for potassium. The letter P is used of phosphorus and Po for polonium.
26. “Covalent” is the term applied to which of the following bonds?
A. Those between an ion and all the surrounding oppositely charged ions
B. The bond between an electrolyte and the surrounding water molecules in a solution
C. Those between non-metal atoms
D. Those between atoms on the left-hand side of the periodic table
Answer is C: Non-metals share electrons when they react with each other (rather than losing or gaining), hence the prefix “co-”.
27. Given that 1 mol is 6 × 1023 particles, how much is a millimole?
A. 6 × 1020 particles
B. 106 mol
C. 10−6 mol
D. 6 × 10−3 particles
Answer is A: A millimole is one-thousandth of a mole, so 1 mmol = 10−3 × 6 × 1023= 6 × 1020 particles.
28. Which of the following is a definition of a molecule? The particle that
composes:
A. Covalent compounds
B. Non-metal elements
C. Electrolytes
D. Ionic compounds
Answer is A: This is one definition of a molecule.
29. What is the smallest particle of a non-metal element known as?
A. A molecule
B. An atom
C. An ion
D. A neutron
Answer is B: An atom is the smallest particle of any element—not just non-metals!
30. What is the difference between ions and molecules?
A. Ions have an electrical charge, whereas molecules do not.
B. Ions are from metal elements only, whereas molecules contain only non-metal elements.
C. Ions arise from compounds between non-metal elements, whereas molecules arise from metal and non-metal elements.
D. An ion may be formed from a single atom, but molecules always involve more than one atom.
Answer is D: This is the only correct choice. However, molecules may also form ions—polyatomic ions.
31. Of the four different types of matter listed below, which is not an example of an element?
A. Hydrogen
B. Oxygen
C. Water
D. Gold
Answer is C: Water is a compound of H and O.
32. A certain pure substance, A, when heat is changed into two quite different pure substances, C and D. Which of the following statements must be true?
A. A is a compound.
B. C and D are not elements.
C. A, C and D are all compounds.
D. C and D are elements.
Answer is A: Only this choice must be true. The others are just possible.
33. Which of the following statements about atoms is FALSE?
A. They are mostly empty spaces.
B. Nearly all their mass is concentrated in the nucleus.
C. In a neutral atom protons and electrons are equal in number.
D. The nucleus contains equal numbers of protons and neutrons.
Answer is D: For the elements with smaller atoms, usually, this is true. For heavier elements, it is not.
34. In which of the following sequences are particles listed in order of increasing size from left to right?
A. Electron, atom, proton, molecule
B. Molecule, atom, proton, electron
C. Atom, proton, electron, molecule
D. Electron, proton, atom, molecule
Answer is D: An electron so far is immeasurably small, while a molecule must have at least two atoms and the proton is a sub-atomic particle.
35. Which of the following is the name of a subatomic particle?
A. Anion
B. Cation
C. Molecule
D. Neutron
Answer is D: A neutron is one of the constituents of the atomic nucleus.
36. Two atoms have the same mass number but different atomic numbers. Which of the following statements concerning these atoms is TRUE?
A. Each has the same number of neutrons in its nucleus.
B. They are isotopes.
C. They are atoms of different elements.
D. Each has the same number of protons in its nucleus.
Answer is C: Different atomic numbers mean different numbers of protons and hence different elements.
37. What is the atomic number of the element occupying Group VA and Period 4 of the periodic table?
A. 33
B. 34
C. 51
D. 52
Answer is A: This is arsenic (As)—you need to consult a periodic table to answer this.
38. Some atoms of iodine, I, contain 53 protons and 78 neutrons in their nuclei. A correct symbol for these atoms would be:
A. 53131I
B. 5378 I
C. 78131I
D. 7853 I
Answer is A: The convention is: the number of protons is the subscript; the sum of the number of protons and neutrons (131) is superscript.
39. Which of the following atoms normally forms ions having a single, positive charge?
A. Mg
B. S
C. Cl
D. K
Answer is D: This is because potassium is a metal and is from group IA of the periodic
table.
40. Which of the following statements concerning isotopes is FALSE?
A. They contain the same number of protons in their atoms.
B. They contain the same number of electrons in their atoms.
C. They contain the same number of neutrons in their atoms.
D. They have very similar chemical properties.
Answer is C: Having a different number of neutrons (while having the same number of protons) is what defines them to be isotopes.
41. The element nitrogen exists as molecules, N2. Which of the following representations of the bonding in a molecule of nitrogen is correct?
A. N+ N−
B. N–N
C. N=N
D. N≡N
Answer is D: Nitrogen is placed in period VA of the periodic table and so needs to share three electrons. That is, needs to form three covalent bonds.
42. Which of the following properties is least likely to be possessed by a covalent, molecular substance?
A. Strong odour
B. High solubility in water
C. Melting point above 400 °C
D. Low electrical conductivity
Answer is C: A high melting point is characteristic of ionic substances. Some covalent compounds are soluble in water.
43. What is the reason that a polar bond between two atoms is so named?
A. The atoms share the electrons equally.
B. The atoms share electrons unequally.
C. The atoms share a pair of electrons.
D. The bond is ionic and occurs between an anion and a cation.
Answer is B: When a pair of electrons are unequally shared, they are located closer to one of the bonding atoms. This makes that atom slightly negative compared to the other atom, hence the molecule has two poles.
44. The formula for glucose is C6H12O6. How many atoms of each type of elements are there in a molecule of glucose?
A. 6 atoms of calcium; 12 atoms of helium, 6 atoms of osmium
B. 1 atom of carbon; 6 atoms of hydrogen, 12 atoms of oxygen
C. 1 atom of carbon; 18 atoms of hydrogen, 6 atoms of oxygen
D. 6 atoms of carbon; 12 atoms of hydrogen, 6 atoms of oxygen
Answer is D: The number of atoms, written as a subscript, immediately follows the symbol for the element and C, H, O are the symbols for carbon, hydrogen and oxygen, respectively.
45. The formula for oleic acid (a fatty acid) may be written as:
CH3(CH2)7CH=CH(CH2)7CO2H. How many atoms of each type of elements are there in a molecule of oleic acid?
A. 18 atoms of carbon; 11 atoms of hydrogen, 1 atom of oxygen
B. 12 atoms of carbon; 10 atoms of hydrogen, 2 atoms of oxygen
C. 18 atoms of carbon; 34 atoms of hydrogen, 2 atoms of oxygen
D. 20 atoms of carbon; 23 atoms of hydrogen, 1 atom of oxygen
Answer is C: The number of atoms written as a subscript immediately follows the symbol for the element, hence there are 2 atoms of oxygen (O). The number 7 outside the parentheses means that there are 7 lots of the atoms that are inside the parentheses. Hence, 14 + 14 H inside the parentheses, with a further 6 H outside them, which totals 34 H.
46. The formula for leucine (an amino acid) may be written as: (CH3)2C3H4NH2COOH. How many atoms of each type of elements are there in a molecule of leucine?
A. 6 atoms of carbon; 13 atoms of hydrogen, 2 atoms of oxygen, 1 atom of nitrogen
B. 5 atoms of carbon; 8 atoms of hydrogen, 2 atoms of oxygen, 1 atom of sodium
C. 6 atoms of carbon; 13 atoms of hydrogen, 2 atoms of oxygen, 1 atom of natrium
D. 8 atoms of carbon; 10 atoms of hydrogen, 2 atoms of oxygen, 1 atom of nitrogen
Answer is A: The number of atoms immediately follows the symbol for the element as a subscript. A number following a parenthesis multiplies the atoms inside the parenthesis. Hence there are 6 atoms of carbon (including 2 inside the parenthesis). By the same reasoning, there are 13 atoms of hydrogen (including 6 inside the parenthesis). An amino acid always has an atom of nitrogen.
47. What may be stated about a chemical bond between atoms that is polar? They occur:
A. Between a metal and a non-metal atom
B. Between two non-metal atoms
C. Between two non-metal atoms that are different to each other
D. When the electrons in the bond are shared equally
Answer is C: Choice B is wrong if the two atoms are the same e.g. if both are oxygen. Choice D is wrong as it implies a non-polar bond.
48. What may be stated about a molecule that is polar?
A. It is probably soluble in polar liquids such as lipids.
B. The molecule has a highly symmetrical shape.
C. It is likely to be soluble in non-polar liquids such as lipids.
D. One end of the molecule will contain different atoms from the opposite end.
Answer is D: A polar molecule has opposite ends (poles) that are different from each other. That is, the molecule is not symmetrical. Choice A is wrong as lipids are not polar liquids.
49. Which of the following best describes the electrolytes that are dissolved in blood?
A. Positive ions
B. Any charged particle
C. Molecules with an electric charge
D. Negative ions
Answer is B: The term electrolyte is applied to any species of dissolved particle that
has an electric charge.
50. The formula for the bone mineral calcium hydroxyapatite is Ca10(PO4)6(OH)2. How many atoms of each element are there in this molecule?
A. 10 atoms of calcium, 6 atoms of phosphorus, 26 atoms of oxygen and 2 atoms of hydrogen
B. 10 atoms of calcium, 6 atoms of phosphorus, 5 atoms of oxygen and 2 atoms of hydrogen
C. 10 atoms of cadmium, 4 atoms of phosphorus, 8 atoms of oxygen and 2 atoms of hydrogen
D. 10 atoms of calcium, 6 atoms of polonium, 1 atom of oxygen and 2 atoms of hydrogen
Answer is A: The number of atoms is written as a subscript and immediately follows the symbol for the element. Hence there are 10 atoms of calcium. When the subscript is outside the parenthesis, it refers to all of the atoms enclosed by the parentheses. Hence there are 6 atoms of phosphorus, 2 of hydrogen and (4 × 6) + (1 × 2) = 26 of oxygen. Ca is the symbol for calcium. Cadmium has the symbol Cd. Polonium has the symbol Po (not PO).
51. Urea has the formula CH4N2O. Identify the elements, and how many atoms of each element are present in a molecule of urea.
A. 1 molecule of methane and 1 of di-nitrogen oxide
B. 1 of carbon, 4 of hydrogen, 2 of nitrogen, 1 of oxygen
C. 1 of calcium, 4 of hydrogen, 2 of ammonia, 1 of oxygen
D. 1 of carbon, 1 of hydrogen, 4 of nitrogen, 2 of oxygen
Answer is B: The elements are carbon, hydrogen, nitrogen and oxygen. The subscript number immediately after the symbol states how many of each atom there are. Hence 4 atoms of hydrogen.
52. Which of the following is the ion of a metal element?
A. Na+
B. NH4+
C. Cl−
D. HCO3−
Answer is A: A metal element loses an electron in chemical reactions so that its number of protons outnumbers the electrons which leave it with a positive charge. Choice B, while being a positive ion, is a compound, not an element.
53. Which of the following is the ion of a non-metal element?
A. H3O+
B. NH4+
C. Cl−
D. HCO3−
Answer is C: While all of the elements represented by symbols in the four choices are non-metals, only choice C represents an element. All others are compounds.
54. Which of the following is the ion of a non-metal element?
A. K2+
B. Mg2+
C. Na+
D. Cl−
Answer is D: A non-metal element gains one (or more) electrons in a chemical reaction so that its number of electrons outnumbers the protons which gives it a negative charge. The other three choices are metal elements, which result in ions with a positive charge.
55. What is the definition of a chemical element?
A. One of earth, air, water and fire.
B. A simple substance that cannot be made into simpler substances by physical means.
C. A pure substance that cannot be made into simpler substances by chemical means.
D. A pure substance that cannot be made into simpler substances by ordinary physical or chemical means.
Answer is D: An element is “pure”, so it contains only one type of substance. It is not a combination of simpler substances so it cannot be made into simpler substances. Nuclear reactors and high-energy particle accelerators can convert elements into other things, but they are not considered to be “ordinary physical or chemical means”. Choice A does not refer to science.
56. What is the definition of an atom?
A. They are the particles of which an element is composed.
B. They are the particles of which a compound is composed.
C. They are the particles of which an ionic compound is composed.
D. They are the particles of which a covalent compound is composed.
Answer is A: An atom is the smallest particle of an element. They are the particles of which an element is composed. The atoms of an element are different from the atoms of all other elements.
57. What is the definition of a proton?
A. They are the subatomic particles within the nucleus of an atom.
B. They are subatomic particles with a positive electrical charge within the nucleus of an atom.
C. They are subatomic particles with a negative electrical charge within the nucleus of an atom
D. They are subatomic particles within the nucleus of an atom but without an electrical charge.
Answer is B: Protons are subatomic particles (smaller than an atom). They have a positive electrical charge. They are, along with neutrons, one of the types of particles that is within the nucleus (the tiny but dense central structure) of an atom.
58. What is the definition of a neutron?
A. They are the subatomic particles within the nucleus of an atom.
B. They are subatomic particles with a positive electrical charge within the nucleus of an atom.
C. They are subatomic particles within the nucleus of an atom but without an electrical charge.
D. They are subatomic particles with a negative electrical charge within the nucleus of an atom
Answer is C: Neutrons are subatomic particles (smaller than an atom). They do not have an electrical charge (they are “neutral”). They are, along with protons, one of the types of particles that is within the nucleus (the tiny but dense central structure) of an atom.
59. What is the definition of an electron?
A. They are the subatomic particles within the atom.
B. They are the subatomic particles within the atom but not in the nucleus.
C. They are the subatomic particles within the atom but outside the nucleus and possess a negative electrical charge.
D. They are the subatomic particles within the atom but outside the nucleus and possess a positive electrical charge.
Answer is D: Electrons are subatomic particles (smaller than an atom). They have a negative electrical charge (i.e. they are attracted to positively charged objects). They exist within the atom but outside of the nucleus and so occupy most of the volume but only a tiny amount of the mass of an atom.
60. What is the definition of a metal element?
A. The atoms of a metal element lose electrons when they participate in chemical reactions.
B. The atoms of a metal element gain electrons when they participate in chemical reactions
C. The atoms of a metal element share electrons when they participate in chemical reactions with atoms of other metal elements.
D. The atoms of a metal element share electrons when they participate in chemical reactions
Answer is A: The atoms of a metal element lose (one or more) electrons when they participate in chemical reactions with non-metal atoms. This transforms them into “ions” with a positive charge. People who are not chemists use the term “electrolyte” as a synonym for “ion”. Metal elements are listed on the “left-hand side” of the periodic table. (The atoms of a non-metal element gain electron(s) when they participate in chemical reactions with metal atoms.)
61. What is the definition of a non-metal element?
A. The atoms of a non-metal element lose electrons when they participate in chemical reactions.
B. The atoms of a non-metal element gain electrons when they participate in chemical reactions.
C. The atoms of a non-metal element share electrons when they participate in chemical reactions.
D. The atoms of a non-metal element gain electrons when they participate in chemical reactions with atoms of metal elements.
Answer is D: The atoms of a non-metal element gain (one or more) electrons when they participate in chemical reactions with metal atoms. This transforms them into “ions” with a negative charge. People who are not chemists use the term “electrolyte” as a synonym for “ion”. Non-metal elements are listed on the “right-hand side” of the periodic table. (In addition, the atoms of a non-metal element share electrons with atoms of other non-metal atoms when they participate in chemical reactions.)
62. What is the definition of an ion?
A. An ion is an atom that has lost an electron so has a positive electrical charge.
B. An ion is an atom or molecule that has lost or gained an electron and has either a positive or negative electrical charge (respectively).
C. An ion is an atom that has lost or gained an electron and has either a positive or negative electrical charge (respectively).
D. An ion is an atom that has gained an electron and has a negative electrical charge.
Answer is B: Both atoms or molecules can become ions. That is, can possess an electrical charge, and that charge may be either positive (if an electron has been lost) or negative (if an electron has been gained).
63. What is the definition of a molecule?
A. A molecule is a small independent group of two or more ions joined together.
B. A molecule is a grouping of ions such that an ion of one charge, is completely surrounded and joined to, a group of ions of the opposite charge.
C. A molecule is a small independent group of two or more atoms joined together.
D. A molecule is a small independent group of two or more atoms of different elements joined together.
Answer is C: A molecule is a group of two or more atoms joined together. The atoms may be from the same element, e.g. O2, or from different elements, e.g. C6H12O6. This group of (2 or 24 in the examples given) atoms remain joined together as they move about.
64. What is the definition of a chemical compound?
A. A pure substance is formed when atoms from two or more elements join together.
B. A pure substance is formed when atoms from one or more elements join together.
C. A pure substance is formed when two or more molecules join together.
D. A mixture that contains atoms of different elements not chemically combined.
Answer is A: A compound is a pure substance (contains only one type of substance). They form when atoms from two or more elements join together. Hence O2 and H2 while being molecules, do not compound as they contain only atoms of the same element.
65. What is the definition of a covalent bond? It is the link that joins two:
A. Non-metal atoms together in a molecule
B. Metal atoms together in a molecule
C. Non-metal atoms together in a lattice structure
D. Metal atoms together in a lattice structure
Answer is A: It is the link (in fact a shared pair of electrons) that joins two non-metal atoms together in a molecule. The “co-” part refers to sharing of electrons, and it is between non-metal atoms. The joining of metal atoms to non-metal atoms is something else.
66. How may an ionic bond be described? It is the attraction between:
A. Two or more adjacent molecules.
B. An ion and the surrounding ions are of opposite charge.
C. Atoms within a molecule.
D. Two ions of opposite charge.
Answer is B: When a metal atom reacts with a non-metal atom, it transfers an electron (or more) to the non-metal atom. In this way, the metal atom becomes positively charged while the non-metal atom acquires an equal but opposite charge. It is the attraction between an ion and all of the immediately adjacent surrounding ions of opposite charge (which may number 6) that causes a “continuous lattice” structure to form.
67. What is the definition of an ionic (non-molecular) compound?
A. The compound is formed when atoms of a metal element chemically react with atoms of a different metal element.
B. The compound is formed when atoms of a non-metal element react with atoms of a different non-metal element.
C. The compound is formed when atoms of a metal react with atoms of a non-metal substance.
D. The structure that results when ions form a lattice rather than molecules.
Answer is C: The compound is formed when atoms of a metal element react with particles of a non-metal element. In such compounds, the metal atoms lose electrons to become cations while the non-metal atoms gain electrons to become anions. These oppositely charged ions then attract each other to form a lattice structure rather than molecules. Choice B refers to a covalent (molecular) compound.
68. What is the definition of a molecular compound?
A. The compound is formed when atoms of a metal element chemically react with atoms of a different metal element.
B. The compound is formed when atoms of a non-metal element react with atoms of a different non-metal element.
C. The compound is formed when atoms of a metal react with atoms of a non-metal substance.
D. The structure that results when ions form a lattice rather than molecules.
Answer is B: When atoms of a non-metal element chemically react with atoms of a different non-metal element, they share their electrons to form a covalent bond. The resulting group of atoms (which may contain two or three atoms or 20,000–30,000 atoms) is called a molecule and is the smallest particle of the new compound substance. Choice C refers to an ionic (non-molecular) compound.
69. Which of the following may be used to distinguish a metal element from a non-metal element?
A. Metal ions have a negative electrical charge, while non-metal ions have a positive charge.
B. Metals are listed on the “left-hand side” of the periodic table, while non-metals are on the“right-hand side”.
C. Metals gain an electron(s) when they react with non-metals, while non-metals lose an electron(s).
D. Metals ions are called anions, while non-metal ions are called cations.
Answer is B: Metals are listed on the “left-hand side” of the periodic table, while non-metals (except for hydrogen) are on the “right-hand side”. All other choices are wrong, but if stated “in reverse” would be correct.
70. Which of the following may be used to distinguish an electron from a proton?
A. An electron resides in the nucleus of the atom, a proton is in the surrounding atomic volume.
B. An electron has a mass of 1860, while a proton has a mass of one.
C. An electron has a negative electrical charge, a proton has a positive charge.
D. An electron has a negative electrical charge, a proton has no electrical charge.
Answer is C: An electron has a negative charge (and no linear dimensions!) and exists in the space within an atom but outside of the nucleus, a proton has a positive charge, exists in the nucleus of an atom, and is 1860× the mass of an electron.
71. Which of the following may be used to distinguish an atom from an ion?
A. An atom has equal numbers of protons and electrons so is neutral: an ion has a +ve or −ve electrical charge.
B. An atom is the smallest part of a molecule; an ion is the smallest part of an element.
C. An atom may be the combination of two or more elements; an ion is the smallest part of an element.
D. Atoms may be found on the left-hand side of the periodic table; ions are located on the right-hand side.
Answer is A: An atom is the smallest piece of an element and has equal numbers of protons and electrons so is neutral: an ion has a +ve or −ve electrical charge. Ions may consist of one atom (e.g. Na+ or Cl−) two or more atoms of different elements (e.g. HCO3 − or H3O+), in which case they are also molecules.
72. Which of the following may be used to distinguish a cation from an anion?
A. A cation is repelled from a cathode, while an anion is attracted to the cathode.
B. A cation is repelled from a cathode, while an anion is repelled from the anode.
C. A cation is an ion with a −ve charge, anion has a positive charge.
D. A cation is an ion with a +ve charge, and an anion has a negative charge.
Answer is D: A cation is an ion with a +ve charge (and so is attracted to the negatively charged electrode—called the cathode), while an anion has a negative charge (and is attracted to an anode).
73. Which of the following may be used to distinguish an atom from a molecule?
A. An atom is the smallest part of a metal element, and a molecule is the smallest part of a non-metal element.
B. An atom is the smallest part of a covalent compound, and a molecule is the smallest part of an element.
C. An atom is the smallest part of an element, and a molecule is the smallest part of a covalent compound.
D. An atom is the smallest part of a non-metal element, while a molecule is composed of two or more metal elements.
Answer is C: An atom is the smallest part of an element, while a molecule is the smallest part of a covalent compound (it is also a group of two or more atoms that may be from the same element (e.g. a molecule of oxygen gas O2) or from different elements (e.g. H2O)).
74. Which of the following may be used to distinguish an element from a compound?
A. A compound is a simple substance that cannot be broken down into a simpler substances.
B. A compound may only be formed from non-metal elements.
C. An element may be found on the left-hand side of the periodic table; while compounds are located on the right-hand side.
D. An element is a simple substance that cannot be broken down into a simpler substances.
Answer is D: An element is a simple substance that cannot be broken down into a simpler substances. A compound is the result of a chemical reaction between two (or more) elements so that it can be broken down into simpler substances (either it's component elements or other compounds).
75. Which of the following may be used to distinguish an ionic compound (IC) from a molecular compound (MC)?
A. An IC involves a metal element and a non-metal element. An MC involves only non-metal elements.
B. An IC involves only non-metal elements. An MC involves a metal element and a non-metal element.
C. An IC involves only metal elements. An MC involves only non-metal elements.
D. An IC involves only non-metal elements. An MC involves only metal elements.
to become a +ve ion) and a non-metal element (which gains an electron/s to become a −ve ion). A molecular compound involves only non-metal elements which share their electrons (shared electrons form a covalent bond) and result in a cluster of atoms called a molecule.
76. Which of the following may be used to distinguish an ionic bond from a covalent bond?
A. A covalent bond is the attraction between two metal atoms. An ionic bond is an attraction between an ion and the surrounding adjacent ions of the same charge.
B. A covalent bond is the attraction between two non-metal atoms. An ionic bond is an attraction between an ion and the surrounding adjacent ions of the opposite charge.
C. A covalent bond is the attraction between two non-metal atoms. An ionic bond is an attraction between an ion and the surrounding adjacent ions of the same charge.
D. A covalent bond is the attraction between two metal atoms. An ionic bond is an attraction between an ion and the surrounding adjacent ions of the opposite charge.
Answer is B: A covalent bond is an attraction between two non-metal atoms. A non-metal atom may form one, two, three or four such bonds (depending on which element we are considering), and the bond may be a single one (involving a pair of electrons) or be double bonds or even triple ones. An ionic bond is an attraction between an ion and the 6–8 surrounding adjacent ions of the opposite charge. Such attractions result in the formation of a crystal with a continuous lattice structure (rather than molecules).
77. Which list contains metallic elements only?
A. Sodium, potassium, calcium, hydrogen
B. Oxygen, nitrogen, calcium, phosphorus
C. Iron, sodium, potassium, calcium
D. Magnesium, zinc, cobalt, argon
Answer is C: These four elements are located on the left-hand side of the periodic table (and do not include hydrogen).
78. Which elements AND how many atoms of each element are in CH3COOH?
A. One methyl and one carboxylic acid
B. Three hydrogen, one oxygen, two carbon, one helium
C. Two oxygen, two carbon and two hydrogen
D. Two carbon, two oxygen, four hydrogen
Answer is D: In this case, the symbol for each element appears twice in the formula. The given chemical formula for acetic acid indicates its structure. The equivalent molecular formula is C2H4O2 from which it is easier to see how many atoms of each element there are, but it does not indicate how the atoms are joined together.
79. Which statement about Ba2+SO42− is correct?
A. It is an ionic substance with one atom of barium, one of sulphur and four of oxygen.
B. It is an ionic substance with one atom of barium, four atoms of sulphur and four of oxygen.
C. It is a covalent substance with one atom of barium, one of sulphur and four of oxygen.
D. It is a covalent substance with one atom of boron, one of sulphur and four of oxygen.
Answer is A: It is ionic as it is written with the symbols for elements superscripted with +ve and −ve signs to indicate ions. Also because Ba is metal and S and O are non-metals. The sulphate ion has 1 atom of S and 4 of O. “Boran” is not a real element.
80. What features are required for a molecule to be “polar”, that is to have small but opposite electrical charges at different ends of the molecule?
A. The molecule must have polar bonds and be asymmetrical in shape.
B. The molecule must have non-polar bonds and be asymmetrical in shape.
C. The molecule must have polar bonds and be symmetrical in shape.
D. The molecule must have non-polar bonds and be symmetrical in shape.
Answer is A: The molecule must have polar bonds and be asymmetrical in shape. Only covalent bonds between two atoms of the same element are not polar.
81. Which of the following statements about the atom and its nucleus is correct?
A. The nucleus is 10−4 times the size of the atom.
B. The nucleus contains neutrons with a positive charge and protons with no charge.
C. Most of the volume of the atom is occupied by the nucleus, but most of the mass is due to the electrons.
D. The majority of the atom’s mass is due to the electrons.
Answer is A: The nucleus is one ten-thousandth the size of the atom, so is mostly empty space. Protons have a +ve charge, and electrons have a mass that is insignificant when compared to the atom's mass.
82. What charge will an ion of magnesium have?
A. Minus 1
B. Minus 2
C. Plus 1
D. Plus 2
Answer is D: Magnesium is a metal so will have a positive ion. It is also in column two of the periodic table so will have a double positive charge. Alternatively, magnesium has 12 electrons and 12 protons (atomic number 12) so needs to lose two electrons in a chemical reaction to achieve the noble gas configuration of ten electrons like neon. When two electrons are lost, the resulting charge is plus 2.