1. AP Chemistry Chapter 2.1 (Days 3 & 4)
Atoms, Molecules & Ions
AP Chemistry
Chapter 2.1
(Days 3 & 4)

2. Subatomic Particles
Protons and electrons are the only particles that have a charge.
Protons and neutrons have essentially the same mass.
The mass of an electron is so small we ignore it.
Table 2.1

3. Symbols of Elements
Elements are symbolized by one or two letters.

4. Atomic Number
All atoms of the same element have the same number of protons: The atomic number (Z)
In a neutral atom, the # of p+ = the # of e-

5. Atomic Mass
The mass of an atom in atomic mass units (amu) is the total number of protons and neutrons in the atom. Remember, electron mass is so tiny we essentially ignore it.

6. Isotopes
Atoms of the same element with different masses.
Isotopes have different numbers of neutrons. 11 6 C 12 6 C 13 6 C 14 6 C

7. How many neutrons are there in an atom of 14C?6 8 12 14

8. C Correct Answer: 6 8 12 14 Mass number Atomic number 14 6
The difference between the mass number and the atomic number is the number of neutrons (14  6) = 8.

9. Determining the Number of Subatomic Particles in Atoms
How many protons, neutrons, and electrons are in (a) an atom of 197Au (b) an atom of strontium-90?

10. Determining the Number of Subatomic Particles in Atoms
How many protons, neutrons, and electrons are in (a) a 138Ba atom, (b) an atom of phosphorus-31?
Answer: (a) 56 protons, 56 electrons, and 82 neutrons; (b) 15 protons, 15 electrons, and 16 neutrons.

11. Periodic Table A systematic catalog of elements.
Elements are arranged in order of atomic number.

12. Periodicity
When one looks at the chemical properties of elements, one notices a repeating pattern of reactivities.

13. Periodic Table The rows on the periodic chart are periods or series.
Columns are groups or families.
Elements in the same group have similar chemical properties.

14. Groups
These five groups are known by their names.

15. Solids, Liquids, & Gases

16. Metals, Nonmetals, Semimetals
Metals – good conductors, high luster, ductile, malleable 16

17. Metals, Nonmetals, Semimetals
Nonmetals – most are gases, poor conductors, brittle 17

18. Metals, Nonmetals, Semimetals
Semi-metals (metalloids) – have properties similar to metals and nonmetals 18

19. Diatomic Molecules
These seven elements occur naturally as molecules containing two atoms:
Hydrogen & draw a 7 starting at N (element 7)
Hockey stick & puck
BrINClHOF (Brinklehoff)
I Have No Bright Or Clever Friends

20. Compounds and Chemical Formulas
Molecule - A single particle, contains two or more nonmetal atoms; covalently bonded
Formula Unit – a particle containing a metal with a nonmetal; ionicly bonded
Chemical formulas – give the number of atoms of each element in a compound

21. Identifying Ionic and Molecular Compounds
Which of the following compounds would you expect to be ionic: N2O, Na2O, CaCl2, SF4?
Which of the following compounds are molecular: CBr4, FeS, P4 O6, PbF2 ?
Answer: CBr4 and P4 O6

22. Identifying Ionic and Molecular Compounds
Which of the following compounds are molecular: CBr4, FeS, P4 O6, PbF2 ?
Answer: CBr4 and P4 O6

23. Which combination is likely to produce an ionic compound?
C and H
S and Cl
Ca and F
Br and I
Xe and F

24. Which combination is likely to produce an ionic compound?
C and H
S and Cl
Ca and F
Br and I
Xe and F

25. Compounds and Chemical Formulas
Chemical formulas – give the number of atoms of each element in a compound

26. Compounds and Chemical Formulas
State the composition for a molecule of trinitrotoluene, TNT: C7H5(NO2)3
7 carbon atoms, 5 hydrogen atoms, 3 nitrogen atoms, 6 oxygen atoms; 21 atoms total

27. Types of Formulas
Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound.
Molecular formulas give the exact number of atoms of each element in a compound.
Sometimes they can be the same

28. Relating Empirical and Molecular Formulas
Write the empirical formulas for the following molecules: (a) glucose, a substance also known as either blood sugar or dextrose, whose molecular formula is C6H12O6; (b) nitrous oxide, a substance used as an anesthetic and commonly called laughing gas, whose molecular formula is N2O.
Answer:  BH3
Give the empirical formula for the substance called diborane, whose molecular formula is B2H6.

29. Relating Empirical and Molecular Formulas
Give the empirical formula for the substance called diborane, whose molecular formula is B2H6.
Answer:  BH3

31. C2H6
CH3

32. Ions
When atoms lose or gain electrons, they become ions.

33. Ions Cation – positive ion Has the “t” like a + sign
Formed by metals and some nonmetals
Lost electrons
#p+ > #e-
Anion – negative ion
Gained electrons
Formed by nonmetals
#p+ < #e-
Polyatomic ions
Made up of two or more atoms
Can be positive or negative
IUPAC – International Union of Pure and Applied Chemistry

34. An isotope of Cr3+ ion containing 24 protons and 27 neutrons would contain ___ electrons.21 24 27 3

35. Correct Answer: 21 24 27 3
The +3 charge indicates there are 3 more protons than electrons:
24  3 = 21

36. Which of the following species has the greatest number of electrons?
Cl
Ca2+
P3 K Ar

37. Correct Answer: Cl Ca2+ P3 K Ar
K has 19 electrons; all the other species listed have only 18 electrons.

38. Writing Chemical Symbols for Ions
Give the chemical symbol, including mass number, for each of the following ions:
(a) The ion with 22 protons, 26 neutrons, and 19 electrons; (b) the ion of sulfur that has 16 neutrons and 18 electrons.
Solution (a) The symbol for the ion is 48Ti3+.
(b) The symbol for the ion is 32S2–.

39. Writing Chemical Symbols for Ions
How many protons and electrons does the Se2– ion possess?
Answer: 34 protons and 36 electrons

40. Isoelectronic
Atoms and ions are considered isoelectronic when they have the same number of electrons.

41. Which of the following are isoelectronic?5. 1. 2. 3. 4.
None of the above

42. Which of the following are isoelectronic?5. 1. 2. 3. 4.
None of the above

43. Group 1A = 1+

44. Group 2A = 2+

45. Group 3A = 3+

46. Group 5A = 3–

47. Group 6A = 2–

48. Group 7A = 1–

49. Group 4A = varies

50. Monoatomic Ions Transition metals form more than one cation
The Stock System
Iron can be Fe2+ or Fe3+
Iron (II) ion, iron (III) ion
Cu+ and Cu2+

51. Polyatomic Ions
Polyatomic anions usually contain one or more elements combined with oxygen
Most end in “-ate”
Those that end in “-ite” have one less oxygen than “-ate”
Exceptions include
CN1-, cyanide
OH1-, hydroxide
O22-, peroxide
NH41+, ammonium

52. Patterns in Oxyanion Nomenclature
When there are two oxyanions involving the same element:
The one with fewer oxygens ends in -ite
NO2− : nitrite; SO32− : sulfite
The one with more oxygens ends in -ate
NO3− : nitrate; SO42− : sulfate

53. Writing Chemical Formulas
A formula unit is the simplest representative particle in an ionic compound
A formula unit is neutral
Positive and negative charges must cancel out (cation + anion)
Made between a metal & a nonmetal

54. Naming Formula units
The metal is written first followed by the nonmetal
The metal keeps its name, the nonmetal gets the suffix “-ide”
MgO
magnesium oxide
NaCl
sodium chloride
Al2O3
aluminum oxide
CaS
calcium sulfide
K3N
potassium nitride

55. Formula units from names
All formula units have a neutral charge
The + and the – must = zero
Beryllium fluoride
Potassium chloride
Strontium nitride

56. The correct name for the compound, MgC2 is
Carbon magneside
Magnesium carbide
Magnesium carbonate
Manganese dicarbide
Magnesium dicarbide

57. Correct Answer: Carbon magneside Magnesium carbide Magnesium carbonate
Manganese dicarbide
Magnesium dicarbide
In this unusual ionic compound, the cation is magnesium cation (Mg2+) and the anion is carbide or acetylide (C22).

58. The simplest chemical formula for the binary ionic compound CaxNy is
Ca2N
Ca2N3
Ca3N2
Ca3N

59. Correct Answer: Ca2N Ca2N3 Ca3N2 Ca3N
Ca loses two electrons to become Ca2+, while N gains three electrons to become N3. To be neutral, positive charges and negative charges have to balance.

60. Transition metals in formula units
Transition metals have multiple oxidation numbers (aka charges)
Exceptions: Ag+ Cd2+ Zn2+
Must figure out charges from name or formula
iron (II) oxide
CuCl2

61. Naming with polyatomics
Polyatomics end mostly in “-ate” and “-ite”
Exceptions: ammonium (NH4+), hydroxide (OH-), cyanide (CN-), & peroxide (O2-2)
A formula with a polyatomic will have 3 or more different elements.
Only one positive polyatomic: NH4+ ammonium
Ca(NO3)2
K2SO4
aluminum acetate
sodium phosphate

62. The compound, CuSO4, is called
Copper sulfate
Copper (II) sulfide
Copper (I) sulfite
Copper (I) sulfate
Copper (II) sulfate

63. Correct Answer: Copper sulfate Copper (II) sulfide Copper (I) sulfite
Copper (I) sulfate
Copper (II) sulfate
The compound is ionic, derived from the copper(II) cation (Cu2+) and the sulfate anion (SO42).

64. Using Ionic Charge to Write Empirical Formulas for Ionic Compounds
What are the empirical formulas of the compounds formed by (a) Al3+ and Cl– ions, (b) Al3+ and O2 – ions, (c) Mg2+ and NO3– ions?
(a) The formula is AlCl3.
(b) The formula is Al2O3.
(c) The formula is Mg(NO3)2.

65. Using Ionic Charge to Write Empirical Formulas for Ionic Compounds
Write the empirical formulas for the compounds formed by the following ions: (a) Na+ and PO43– , (b) Zn2+ and SO42– , (c) Fe3+ and CO32–.
Answers: (a) Na3PO4, (b) ZnSO4, (c) Fe2(CO3)3

66. Determining the Names of Ionic Compounds from Their Formulas
Name the following compounds: (a) K2SO4 , (b) Ba(OH)2 , (c) FeCl3.
(a) potassium sulfate
(b) barium hydroxide
(c) Iron (III) chloride

67. Determining the Names of Ionic Compounds from Their Formulas
Name the following compounds: (a) NH4Br, (b) Cr2O3, (c) Ca(NO3)2.
Answers: (a) ammonium bromide, (b) chromium(III) oxide, (c) cobalt(II) nitrate

68. Determining the Formulas of Ionic Compounds from Their Names
Write the chemical formulas for the following compounds: (a) potassium sulfide, (b) calcium hydrogen carbonate, (c) nickel(II) perchlorate.
(a) K2S
(b) Ca(HCO3)2
(c) Ni(ClO4)2.

69. Determining the Formulas of Ionic Compounds from Their Names
Give the chemical formula for (a) magnesium sulfate, (b) silver sulfide, (c) lead(II) nitrate.
Answers: (a) MgSO4 , (b) Ag2S, (c) Pb(NO3)2

70. Nomenclature of Binary Molecular Compounds
The less electronegative atom is usually listed first.
A prefix is used to denote the number of atoms of each element in the compound (mono- is not used on the first element listed, however.)

71. Nomenclature of Binary Molecular Compounds
The ending on the more electronegative element is changed to -ide.
CO2: carbon dioxide
CCl4: carbon tetrachloride

72. Nomenclature of Binary Compounds
If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are often elided into one:
N2O5: dinitrogen pentoxide

73. Molecular formulas NO2 P4S10 NI3 Cl2O CO Xenon hexafluoride
Diphosphorus pentaoxide

74. Elements by themselves
Solo elements are always just named for themselves no matter how many there are N2 S8 Fe

75. The molecular compound N2O4 is named:
Nitrogen oxide
Oxygen nitride
Dinitrogen quartoxide
Dinitrogen tetroxide
Nitrous oxide

76. Correct Answer: Nitrogen oxide Oxygen nitride Dinitrogen quartoxide
Dinitrogen tetroxide
Nitrous oxide
Remember: the vowel “A” on the prefix tetra- is dropped because oxide starts with the vowel “O.”

77. Relating the Names and Formulas of Binary Molecular Compounds
Name the following compounds: (a) SO2, (b) PCl5, (c) N2O3.
(a) sulfur dioxide, (b) phosphorus pentachloride, and (c) dinitrogen trioxide.

78. Relating the Names and Formulas of Binary Molecular Compounds
Give the chemical formula for (a) silicon tetrabromide, (b) disulfur dichloride.
Answers: (a) SiBr4, (b) S2Cl2

79. Relating the Names and Formulas of Acids
Name the following acids: (a) HCN, (b) HNO3, (c) H2SO4, (d) H2SO3.
(a) hydrocyanic acid (b) nitric acid (c) sulfuric acid. (d) sulfurous acid

80. Relating the Names and Formulas of Acids
Give the chemical formulas for (a) hydrobromic acid, (b) carbonic acid.
Answers: (a) HBr, (b) H2CO3

81. Acid Nomenclature
If the anion in the acid ends in -ide, change the ending to -ic acid and add the prefix hydro- :
HCl: hydrochloric acid
HBr: hydrobromic acid
HI: hydroiodic acid

82. Acid Nomenclature
If the anion in the acid ends in -ite, change the ending to -ous acid:
HClO: hypochlorous acid
HClO2: chlorous acid

83. Acid Nomenclature
If the anion in the acid ends in -ate, change the ending to -ic acid:
HClO3: chloric acid
HClO4: perchloric acid

84. The acid HClO3 is known as:
Perchloric acid
Chloric acid
Chlorous acid
Hypochlorous acid
Hydrochloric acid

85. The acid HClO3 is known as:
Perchloric acid
Chloric acid
Chlorous acid
Hypochlorous acid
Hydrochloric acid

86. Simple Organic Chemistry and Hydrocarbons
Hydrocarbons contain only two elements: 1) hydrogen, & 2) carbon
simplest hydrocarbons called “alkanes”, which contain only carbon to carbon single covalent bonds (CnH2n+2)
methane (CH4) with one carbon is the simplest alkane. It is the major component of natural gas

87. Simple Organic Chemistry and Hydrocarbons
meth- many
eth- elephants
prop- pee
but- by
pent- plants
hex-
hept-
oct-
non-
dec-

88. Alcohols Alcohols - a class of organic compounds with an -OH group
The -OH functional group in alcohols is called a “hydroxyl” group; thus R-OH is the formula
How is this different from the hydroxide ion? (covalent bonding with the carbon- not ionic with a metal like bases)

89. Alcohols
For IUPAC naming:
drop the -e ending of the parent alkane name; add ending of -ol, number the position of –OH
The hydroxyl is given the lowest position number (1-propanol, 2-propanol)

90. Properties of Alcohols
Many aliphatic alcohols used in laboratories, clinics, and industry
Isopropyl alcohol (2-propanol) is rubbing alcohol; used as antiseptic, and a base for perfume, creams, lotions, and other cosmetics

91. Properties of Alcohols
Ethyl alcohol (ethanol) used in the intoxicating beverages; also an important industrial solvent

92. Writing Structural and Molecular Formulas for Hydrocarbons
Consider the alkane called pentane. (a) Assuming that the carbon atoms are in a straight line, write a structural formula for pentane. (b) What is the molecular formula for pentane?
C5H12

93. Writing Structural and Molecular Formulas for Hydrocarbons
Butane is the alkane with four carbon atoms. (a) What is the molecular formula of butane? (b) What are the name and molecular formula of an alcohol derived from butane?
Answers: (a) C4H10 , (b) butanol, C4H10O or C4H9OH