Chapter 2 – The Components of Matter

Sample Problem 2.1 p. 39Distinguishing Elements, Compounds, and Mixtures at the Atomic Scale

(a) Mixture - 2

molecular elements (green & purple), 1 compound (2 red + 1 yellow)

(b)Element – only one kind of atom

(c)Compound - molecules that each has two black and six blue atoms

Follow-up Problem 2.1

Reactants (left) mixture of two elements

Products (right) compound of molecules made up of one red atom and one blue atom

Sample Problem 2.2 p. 42Calculating the Mass of an Element in a Compound102 kg pitchblende

71.4 kg uranium

1000 g uranium

= 86,500 g uranium

84.2 kg pitchblende

1 kg uranium

= 8.65 x 104 g Uranium

Follow-up Problem 2.2 p. 422.3 t uranium 84.2 t

pitchblende12.8 t oxygen = .41 t oxygen

71.4 t uranium 84.2 t pitchblende

Sample Problem 2.3 p. 44Visualizing Mass Laws

16 atoms on each side (9 green + 7 purple)… mass conservation

The compound formed has 1 purple with 2 green… law of definite composition

Only one compound formed so this is NOT an example of law of multiple

proportions

Follow-up Problem 2.3 p. 44ONLY diagram B… it has molecules of 1 green to 1 red and 3 green to 1 red

The Atomic Theory Today

An atom is an electronically neutral, spherical entity composed of a positively charged central nucleus surrounded by one or more negatively charged electrons.

The atom’s diameter is about 20,000 times the diameter of the nucleus… (The nucleus would be the size of a pea in an atom the size of the Houston Astrodome!)

The nucleus contributes 99.97% of the atom’s mass and only about 1 quadrillionth of its volume… its density is about 1014 g/mL!

The nucleus contains protons and neutronso Protons (p+) have a positive charge o Neutrons (n0) have no charge (neutral)

Electrons (e-) are found outside the nucleus and have a negative charge

An atom is neutral because the number of protons in the nucleus is equal to the number of electrons surrounding the nucleus.

Atomic Number, Mass Number, and Atomic Symbol

The atomic number (Z) of an element equals the number of protons in the nucleus of each atomo All atoms of an element have the same atomic numbero The atomic number for each element is unique to that

elemento 117 known elements

90 occur in nature and 27 have been synthesized by nuclear scientist

The mass number (A) is the total number of protons and neutrons in the nucleus.o Each proton and neutrons contributes one unit to the

mass number A carbon atom with 6 protons and 6 neutrons in

its nucleus has a mass number of 12 The atomic symbol (or element symbol) of an element is

based on its English, Latin, or Greek nameo Sodium gets its symbol (Na) from its Latin name

natrium To calculate the number of neutrons an atom has…

o Number of neutrons = mass number – atomic number

Isotopes

All atoms of an element have the same atomic number but not the same mass number.

Isotopes of an element are atoms that have different numbers of neutrons and therefore different mass numbers

What is the difference between carbon-12 (pictured to the left) and carbon-14?

ANSWER: carbon-12 has 6 protons, 6 neutrons, and 6 electrons… carbon -14 has 6 protons, 8 neutrons, and 6 electrons

What is the difference between oxygen-16 and oxygen-18?

ANSWER: oxygen-16 has 8 protons, 8 neutrons, and 8 electrons… oxygen-18 has 8 protons, 10 neutrons, and 8 electrons.

Sample Problem 2.4 p. 49Determining the Number of Subatomic Particles in the Isotopes of an Element

2814 Si – 14p+, 14e-, 14no

2914 Si – 14p+, 14e-, 15no

3014 Si - 14p+, 14e-, 16no

Follow-up Problem 2.4 p.4911

5 Q – 5p+, 5e-, 6no (Boron)41

20 R – 20p+, 20e-, 21no (Calcium)131

53 X – 53p+, 53e-, 78no (Iodine)

Atomic Masses of the Elements

The mass of an atom is measured relative to the mass of an atomic standardo The modern standard is the carbon-12 atom which is

defined as exactly 12 atomic mass units The atomic mass unit is 1/12 the mass of a

carbon-12 atom 1 atomic mass unit = 1 dalton (Da) Although it is a relative mass it has an

absolute mass of 1.66054 x 10-24 g Mass spectrometry – method for measuring the relative

masses and abundances of atomic-scale particles very precisely.

Example…

Mass of 28 Si atom = 2.331411

Mass of 12C standard

To calculate the isotopic mass of 28 Si

Isotopic mass of 28Si = measured mass ratio x mass of 12C

Isotopic mass of 28Si = 2.331411 x 12 amu

Isotopic mass of 28Si = 27.97693 amu

Atomic Mass (also called atomic weight) – the average of the masses of its natural occurring isotopes

To calculate the atomic mass of an element…

Isotope Mass (amu) Abundance %28Si 27.97693 92.23 % (.9223) 25.8031 amu29Si 28.976495 4.67% (.0467) 1.3532 amu30Si 29.973770 3.10% (.0310) 0.9292 amu

Atomic Mass 28.09 amu

Sample Problem 2.5 p. 52Calculating the Atomic Mass of an Element

Isotope Mass (amu) AbundanceAg - 107 106.90509 .5184 55.42 amuAg - 109 108.90476 .4816 52.45 amu

Atomic Mass 107.87

Follow-up Problem 2.5 p. 5210.0129x + [11.0093 (1- x)] = 10.81

x = .2000 (10B)1- x = .8000 (11B)

Periodic Table

Dmitri Mendeleev (Russian chemist) published the most successful organization of the elements in 1871 (he arranged the elements in order by mass and arranged elements with similar properties in the same column)

The modern periodic table of elements is based on Mendeleev’s version except elements are arranged by atomic number

(1) Elements are arranged in increasing order by atomic number (number of protons in the nucleus)

(2) Horizontal rows are called periods(3) Vertical columns are called groups (or families)

(4) The eight A groups contain the main-group elements(5) The ten B groups contain the transition elements(6) Inner transition elements include the lanthanides and

actinides (pulled out of the main portion of the table at the bottom)

(7) Metals (left of the “staircase”)… shiny, solids at room temperature (mercury is the only liquid), conduct heat and electricity well, malleable (they can be shaped with tools), ductile (can be drawn into wires)

(8) Nonmetals (upper right corner above “staircase”)… gases or dull brittle solids at room temperature (bromine is the only liquid), poor conductors of heat and electricity

(9) Metalloids (lay along the “staircase”)… have properties between those of metals and nonmetals

(10) Alkali metals – Group 1A (except hydrogen)(11) Alkaline earth metals – Group 2A(12) Oxygen family – Group 6A(13) Halogens – Group 7A(14) Noble gases – Group 8A

Compounds : Introduction to Bonding

With a few exceptions, most elements are found in compounds combined with other elements

Elements combine in two general wayso Ionic compounds – transfer electrons from one

element to anothero Covalent compounds – atoms sharing electrons

Both processes generate chemical bonds (Forces that hold atoms together)

Formation of Ionic Compounds

Ionic compounds are composed of ionso Charged particles that form when at atom (or small

group of atoms) gains or loses one or more electronso Simplest type of ionic compound is a binary ionic

compound Typically forms when a metal reacts with a

nonmetal Metal atoms lose one or more electrons and

form a cationo Positively charged ion

Nonmetal atoms gain one or more electrons and form an aniono Negatively charged ion

Metal atoms transfer electrons to nonmetals A cation or anion derived from a single atom is

called a monatomic ion

The Case of Sodium Chloride

Predicting the Number of Electrons Lost or Gained

Ionic compounds are neutral because they contain equal numbers of positive and negative charges (In the case of sodium chloride there are equal numbers of Na+ and Cl- because both are singly chargedo In sodium oxide (where we have Na+ and O2- ions), we

have twice as many Na+ as we have O2-

To predict the number of electrons that a given atom will gain or lose…o For A group elements

Metals lose electrons to form an ion that has the same number of electrons as the nearest noble gas

Group 1A – lose one electron form 1+ ions Group 2A – lose two electrons form 2+ ions Aluminum in Group 3A – loses two

electrons form 3+ ion Nonmetals gain electrons to form an ion that has

the same number of electrons as the nearest noble gas

Group 7A gains one electron forms 1- ions Group 6A gains two electrons forms 2- ions Nitrogen in Group 5A gains three electrons

forms 3- ions

Sample Problem 2.6 p. 57Predicting the Ion an Element Forms

(a) I- [Iodine is in group 7A (17)… so it wants to gain (it is a nonmetal) one more electron to have the same number of electrons as Xe. When it gains one more electron, it now has 17p+ and 18e-. Its net charge is now 1-.]

(b) Ca2+ [Calcium is in group 2A (2)… so it wants to lose (it is a metal) 2 electrons so that it has the same number of electrons as Ar. When it loses 2 electrons, it now has 20p+ and 18e-. Its net charge is now 2+.]

(c) Al3+ [Aluminum is in group 3A (13)… so it wants to lose (it is a metal) 3 electrons so that it has the same number of electrons as Ne. When it loses 3 electrons, it now has 13p+ and 10e-. Its net charge is 3+.]

Follow-up Problem 2.6 p. 57(a) S2- [Sulfur is in group 6A (16)… so it wants to gain (it

is a nonmetal) 2 more electrons so it has the same number of electrons as Ne. When it gains 2 electrons, it now has 16p+ and 18e-. Its net charge is 2-.]

(b) Rb+ [Rubidium is in group 1A (1)… so it wants to lose (it is a metal) 1 electron so it has the same number of electrons as Kr. When it loses 1 electron, it now has 37p+ and 36e-. Its net charge is 1+.]

(c) Ba2+ [Barium is in group 2A (2)… so it wants to lose (it is a metal) 2 electrons so that it has the same number of electrons as Xe. When it loses 2 electrons, it now has 56p+ and 54e-. Its net charge is 2+.]

Formation of Covalent Bonds

Covalent compounds form when elements share electronso Usually occurs between nonmetals

Covalent bond – a pair of electrons mutually attracted by two nuclei

Covalent and Ionic Substances

Most covalent substances consists of moleculeso A cup of water consists of individual water molecules

lying near each other. There are no molecules in ionic compounds

o Covalent bonding involves the mutual attraction between two (positively charged) nuclei and the two (negatively charged) electrons.

An ionic substance such as sodium chloride is a continuous array in three dimensions of oppositely charged sodium and chloride ions, not a collection of individual sodium chloride “molecules.”o Ionic bonding involves the mutual attraction between

positive and negative ions.

Polyatomic Ions: Covalent Bonds Within Ions

Many ionic compounds contain polyatomic ionso An ion that consists of two or more atoms bonded

together covalently and has a net positive or negative charge.

Formulas, Names, and Masses of Compounds

Chemical formula – uses element symbols and often numerical subscripts to show the type and number of each atom in the smallest unit of the substance.

Represents one molecule if it is a molecular substance Represents one formula unit if it is an ionic compound

Binary Ionic CompoundsTwo general rules…

(1) For all ionic compounds, names and formulas give the positive ion (cation) first and the negative ion (anion) second.

(2) For all binary ionic compounds, the name of the cation is the name of the metal, and the name of the anion has the suffix –ide added to the root of the name of the nonmetal.

Example… calcium (metal) + bromine (nonmetal)

bromine become bromide

calcium bromide

Compounds of Elements That Form One Ion

The periodic table presents some key points about the formulas of main-group monatomic ions.

Monatomic ions of main group elements have the same ionic chargeo The alkali metals [1A (1)] form ions with a 1+ chargeo The halogens [7A (17)] form ions with a 1- charge

For cations (positive ions), the ion charge equals A-group number (exceptions are Sn2+ and Pb2+)

For anions (negative ions), the ion charge equals A-group number minus 8o Example… sulfur is in family 6A. (6 – 8 = -2) Sulfur

forms S2-

Main group elements have the same number of electrons as the nearest noble gas (Aluminum has 13p+ and 10e- and thus forms a Al3+ ion)

Formula unit

Ionic compounds consists of an array of ions rather than separate moleculeso The formula of an ionic compound represents the

formula unit A formula unit is the relative numbers of cations

and anions in the compound. The compound has a zero net charge, so the positive charges of the cations balance the negative charges of the anions.

Example… in calcium bromide we have twice as many Br - as Ca2+ [ CaBr2 ]

Reduce the subscripts to the smallest whole numbers… Ca2O2 would be CaO

Sample Problem 2.7 p. 61Naming Binary Ionic Compounds

(a) magnesium nitride (magnesium is the metal and nitrogen is the nonmetal… so magnesium is written first and nitrogen gets an ide ending)

(b) cadmium iodide (cadmium is the metal and iodine is the nonmetal… so cadmium is written first and iodine gets an ide ending)

(c) strontium fluoride (strontium is the metal and fluorine is the nonmetal… so strontium is written first and fluorine gets an ide ending)

(d) cesium sulfide (cesium is the metal and sulfur is the nonmetal… so cesium is written first and sulfur gets an ide ending)

Follow-Up Problem 2.7 p. 61(a) zinc [Group 2B (12)], oxygen [Group 6A (16)](b) silver [Group 1B (11)], bromine [Group 7A (17)](c) lithium [Group 1A (1)], chlorine [Group 7A (17)](d) aluminum [Group 3A (13)], sulfur [Group 6A (16)]

Sample Problem 2.8 p. 61(a) Mg2+ and N3- (you need 3 Mg2+ to get 6+ and 2 N3- to get

6- so that you have a neutral compound) Formula is… Mg3N2

(b) Cd2+ and I - (you need 1 Cd2+ to get 2+ and 2 I - to get 2- so that you have a neutral compound) Formula is… CdI2

(c) Sr2+ and F - (you need 1 Sr2+ to get 2+ and 2 F – to get 2- so that you have a neutral compound) Formula is… SrF2

(d) Cs+ and S2- (you need 2 Cs+ to get 2+ and 1 S2- to get 2- so that you have a neutral compound) Formula is… Cs2S

Follow-Up Problem 2.8 p. 61(a) Zinc is Zn2+ because it is in Group 2B and oxygen is O2-

because it is in Group 6A… You need 1 Zn2+ to get 2+ and you need 1 O2- to get to 2- so that you have a neutral compound… Formula is ZnO

(b) Silver is Ag+ because it is in Group 1B and bromine is Br – because it is in Group 7A… You need 1 Ag+ to get 1+ and 1 Br – to get 1- so that you have a neutral compound… Formula is AgBr

(c) Lithium is Li+ because it is Group 1A (1) and chlorine is Cl – because it is in Group 7A (17)… You need 1 Li+ to get 1+ and 1 Cl – to get 1- so that you have a neutral compound… Formula is LiCl

(d) Aluminum is Al3+ because it is in Group 3A (13) and sulfur is S2- because it is in Group 6A (16)… You need 2 Al3+ to get 6+ and 3 S2- to get 6- so that you have a neutral compound… Formula is Al2S3

Compounds with Metals That Form More Than One Ion

Many metals, especially the transition metals (B groups), can form more than one ion…

Names of compounds containing these elements (and others) that form more than one ion include a Roman numeral within parentheses immediately after the metal ion’s name to indicate its ionic charge.

Examples – FeCl2 is named iron (II) chloride and FeCl3 is named iron (III) chloride

Trivial name rules…

(a) The suffix –ous for the ion with the lower charge(b) The suffix –ic for the ion with the higher charge

Examples – iron (II) chloride is also called ferrous chloride and iron (II) chloride is also called ferric chloride

Sample Problem 2.9 p. 62

Determining Names and Formulas of Ionic Compounds of Metals That Form More Than One Ion

(a) Sn2+ because the name told you tin (II) and F – because F is in Group 7A (17)… the formula is SnF2 (Because you need 1 Sn2+ to get 2+ and 2 F – to get 2- so that you have a neutral compound)

(b) You determine Cr is Cr3+ because there are 3I – in the formula so you have 3-… there is only 1 Cr in the formula so you know it has to be 3+ so that you have a neutral compound. The name is chromium (III) iodide (the Roman numeral in parentheses is necessary because chromium forms more than one ion… Cr2+ and Cr3+)

(c) Ferric tells you it is Fe3+ and oxygen is O2- because it is in Group 6A (16)… so you would need 2 Fe3+ to get 6+ and you need 3 O2- to get 6-… the formula is Fe2O3

(d) You determine Co is Co2+ because there is 1 S2- in the formula so you have 2-… there is 1 Co in the formula so you know it has to be 2+ so that you have a neutral compound. The name is cobalt (II) sulfide (the Roman numeral in parentheses is necessary because cobalt forms more than one ion… Co2+ and Co3+)

Follow-up Problem 2.9 p. 62(a) Lead (IV) tells you Pb4+ and you know that oxygen is O2-

because it is in Group 6A (16). You need 1 Pb4+ to have 4+ and you would need 2 O2- to have 4- so that you have a neutral compound. The formula is PbO2

(b) The formula tells you that you have 1 S2-. [we know that sulfur is 2- because it is in Group 6A (16)] Since the formula tells us that we have 2 Cu, Cu must be Cu+1. 1 S2- gives us 2- and 2 Cu+ give us 2+ so that we have a neutral compound. The name of the compound is copper (I) sulfide (the Roman numeral in parentheses is necessary because copper forms more than one ion… Cu+ and Cu2+)

(c) The formula tells us that we have 2 bromines. Each bromine is Br -. We know that bromine is 1- because bromine is in Group 7A (17). So from the bromines we have 2-. Since we have only 1 Fe in the formula, that means that Fe is 2+. The name of the compound is iron (II) bromide (the Roman numeral in parentheses is necessary because iron forms more than one ion… Fe2+ and Fe3+)

(d) Mercuric tells us that it is Hg2+ and we know that chlorine is Cl – because it is in Group 7A (17). We need 1 Hg2+ to give us 2+ and 2 Cl – to give us 2- so that we have a neutral compound. So the formula is HgCl2

Compounds That Contain Polyatomic IonsMany ionic compounds contain polyatomic ions. The table below lists the common polyatomic ions…

Formula for potassium nitrate is KNO3 because potassium is K+ and nitrate is NO3

- (1 of each ion makes a neutral compound)

Formula for sodium carbonate is Na2CO3 because sodium is Na+ and carbonate is CO3

2- (2 Na+ combine with 1 CO3

2- to make a neutral compound)

Formula for calcium nitrate is Ca(NO3)2 because calcium is Ca2+ and nitrate is NO3

– (1 Ca2+ combines with 2 NO3

– to make a neutral compound. Note when you use more than one polyatomic ion in a formula, you need to place it in parentheses with a subscript noting the number of ions needed to make a neutral compound.

Families of Oxoanions

Most polyatomic ions are oxoanions, or oxyanions. (Those in which an element, usually a nonmetal is bonded to one or more oxygen atoms) There are several families of two or four oxoanions that differ only in the number of oxygen atoms.

Rules when we have two oxoanions in a familyo The ion with more oxygen atoms takes the nonmetal

root and the suffix –ate.

o The ion with less oxygen atoms takes on the nonmetal root and the suffix –ite.

Examples… SO4

2- is sulfate and SO32- is sulfite

NO3 – is nitrate and NO2 – is nitrite

Rules when you have four oxoanions in a familyo The ion with the most oxygen atoms has the prefix

per, the nonmetal root, and the suffix –ate.o The ion with one fewer oxygen atoms has just the root

and the suffix –ate.o The ion with two fewer oxygen atoms has just the root

and the suffix –ite.o The ion with the least (three fewer) oxygen atoms has

the prefix hypo, the root, and the suffix –ite. Examples…

Chlorine oxoanionso ClO4 – is perchlorateo ClO3 – is chlorateo ClO2 – is chloriteo ClO – is hypochlorite

Bromine oxoanionso BrO4 – is perbromateo BrO3 – is bromateo BrO2 – is bromiteo BrO – is hypobromite

Iodine oxoanionso IO4 – is periodateo IO3 – is iodateo IO2 – is iodite

o IO – is hypoiodite

Hydrated Ionic Compounds

Ionic compounds called hydrates have a specific number of water molecules in each formula unit, which is shown after a centered dot in the formula and noted in the name by a Greek numerical prefix and the word hydrate. The Greek prefixes are…

Example… MgSO4 7H2O would be named magnesium sulfate heptahydrate

Example… CaSO4 2H2O would be named calcium sulfate dihydrate

Example… CuSO4 5H2O would be named copper (II) sulfate pentahydrate

Sample Problem 2.10 p. 63Determining Names and Formulas of Ionic Compounds Containing Polyatomic Ions

(a) ClO4 – is perchlorate, which has a 1- charge. Since there

are two perchlorates in the formula, this is a total of 2-. Since there is only one Fe in the formula, it must be Fe2+ because that would give us a neutral compound (2- and 2+) The name would be iron (II) perchlorate

(b) Sodium is Na+ and sulfite is SO32-. You would need two

Na+ and one sulfite to make a neutral compound, so the formula would be Na2SO3

(c) Ba2+ is barium and OH – is hydroxide. There are 8 water molecules for each formula unit. The name would be barium hydroxide octahydrate

Follow-Up Problem 2.10 p. 63(a) Cupric tells me Cu2+ and nitrate tells me NO3

- . You need 2 NO3

– for each Cu2+ in the formula to create a neutral compound. Trihydrate tells me that I have three waters. The formula would be Cu(NO3)2 3H2O

(b) Zinc is Zn2+ and hydroxide is OH- , so you need 2 OH- and 1 Zn2+ to make a neutral compound. The formula would be Zn(OH)2

(c) Li+ is lithium and CN- is cyanide. The name is lithium cyanide

Sample Problem 2.11 p. 64Recognizing Incorrect Names and Formulas of Ionic Compounds

(a) Prefixes are not used in naming ionic compounds. The name would simply be barium acetate

(b) You only place parentheses around polyatomic ions when you are using more than one. Sulfide is S2- not SO3

2-. The correct formula would be Na2S(c) Iron II would be Fe2+ and sulfate is SO4

2- so they would simply combine in a 1:1 ratio. The correct formula would be FeSO4

(d) Cesium is Cs+ and carbonate is CO32-. You would need 2

Cs+ and 1 CO32- to make a neutral compound. The

correct formula would be Cs2CO3.

Follow-Up Problem 2.11 p. 64(a) Ammonium is NH4

+ and phosphate is PO43-. You would

need 3 NH4+ and 1 PO4

3- to make a neutral compound. The correct formula would be (NH4)3PO4

(b) When you use more than one polyatomic ion, it needs to go in parentheses with a subscript. The correct formula would be Al(OH)3

(c) Mg is magnesium (not manganese) and it is Mg2+ as an ion (it is in Group 2A) and HCO3

- is bicarbonate. The correct name is magnesium bicarbonate

(d) Do not use the –ic ending with Roman numerals and NO3

- is nitrate. The correct name would be chromium (III) nitrate or chromic nitrate

(e) Ca is calcium and NO2- is nitrite. The correct name

would be calcium nitrite

Acid Names from Anion Names

When naming acids and writing the formulas for acids we consider acids as anions that are connected to the number of hydrogen ions (H+) needed for charge neutrality. The two common types of acids are binary acids and oxoacids.

Binary acids form when certain gaseous compounds dissolve in water and form an aqueous solution. (Hydrogen plus one other element… two (bi) total elements or an anion that ends in –ide)o When naming binary acids, you add the prefix hydro

and the suffix –ic to the nonmetal root and then the word acid

HCl (aq) would be hydrochloric acid HBr (aq) would be hydrobromic acid HI (aq) would be hydroiodic acid

Oxoacids names are similar to those of the oxoanions, except for two suffix changeso Oxoanions that end in –ate become –ic in the acid

BrO3 – is bromate, so HBrO3 (aq) is bromic acid

o Oxoanions that end in –ite become –ous in the acid IO2

– is iodite, so HIO2 (aq) is iodous acid

Sample Problem 2.12 p. 65Determining Names and Formulas of Anions and Acids

(a) Br – will form a binary acid with H+. The correct name would be hydrobromic acid / HBr

(b) IO3 – will form an oxoacid with H+. Since IO3

– is iodate, the acid would be named iodic acid / HIO3

(c) CN – is an anion that ends in –ide (cyanide), so it follows the binary acid rules. The correct name would be hydrocyanic acid / HCN

(d) SO42 – is the sulfate ion and will form an oxoacid with H+.

Since sulfate ends in –ate the acid’s name would be sulfuric acid / H2SO4.

(e) NO2 – is the nitrite ion and will form an oxoacid with H+.

Since nitrite ends in –ite the acid’s name will end in –

ous. The correct name of the acid would be nitrous acid / HNO2

Follow-Up Problem 2.12 p. 65(a) Chloric has an –ic ending so that means it has the

chlorate ion… The chlorate ion is ClO3 – and hydrogen

is H+ so the formula would be HClO3.(b) HF is a binary acid (only two elements) so it follows

those rules. The name is hydrofluoric acid.(c) Acetic means it has the acetate ion which is C2H3O2

– or CH3COO –. So the formula would be HC2H3O2 or CH3COOH

(d) Sulfurous tells us that it has the sulfite ion which is SO32-

So the correct formula would be H2SO3

(e) BrO – is the hypobromite ion. The correct name would be hypobromous acid.

Binary Covalent CompoundsBinary covalent compounds are typically formed by the combination of two nonmetals. Some are so familiar that we use their common names, such as ammonia (NH3), methane (CH4), and water (H2O), but most are named systematically.

Rules For Naming Binary Covalent Compounds

The element with the lower group number in the periodic table comes first in the name. The element with the higher group number comes second and is named with its root and the suffix –ide.

o Exception… When the compound contains oxygen and any of the halogens chlorine, bromine, or iodine, the halogen is named first.

o If both elements are in the same group in the periodic table, the one with the higher period number is named first.

Covalent compounds use Greek numerical prefixes to indicate the number of atoms of each element. The first element in the name has a prefix only when more than one atom of it is present; the second usually has a prefix.

Example… NF3 is nitrogen trifluoride

Example… H2O is dihydrogen monoxide

Example… CO2 is carbon dioxide

Example… CCl4 is carbon tetrachloride

Sample Problem 2.13 p. 65Determining Names and Formulas of Binary Covalent Compounds

(a) CS2 (1 carbon and 2 sulfurs)(b) phosphorus pentachloride (1 phosphorus and 5

chlorines)(c) N2O4 (dinitrogen tetraoxide)

Follow-Up Problem 2.13 p. 65

(a) sulfur trioxide(b) silicon dioxide(c) N2O(d) SeF6

Sample Problem 2.14 p. 66Recognizing Incorrect Names and Formulas of Binary Covalent Compounds

(a) SF4 is sulfur tetrafluoride(b) dichlorine heptaoxide is Cl2O7

(c) dinitrogen trioxide

Follow-Up Problem 2.14 p. 66(a) disulfur dichloride(b) NO(c) Bromine trichloride

Molecular Masses from Chemical Formulas Molecular Mass = sum of atomic masses

o Example… H2O Molecular mass = (2 x atomic mass of hydrogen)

+ (1 x atomic mass of oxygen) Molecular mass = (2 x 1.008 amu) + (1 x 16.00) Molecular mass = 18.02 amu

Formula Mass from Chemical Formulas

Ionic compounds do not consists of molecules, so the mass of a formula unit is termed the formula masso Example… Ba(NO3)2

Formula mass = sum of atomic masses Formula mass = (1 x atomic mass of barium) + (2

x atomic mass of nitrogen) + (6 x atomic mass of oxygen)

Formula mass = (1 x 137.3 amu) + (2 x 14.01 amu) + (6 x 16.00 amu)

Formula mass = 261.3 amu

Sample Problem 2.15 p. 67Calculating the Molecular Mass of a Compounds

Molecular mass P4S3 = sum of atomic masseso Molecular mass P4S3 = (4 x atomic mass of

phosphorus) + (3 x atomic mass of sulfur)o Molecular mass P4S3 = (4 x 30.97 amu) + (3 x 32.07

amu)o Molecular mass P4S3 = 220.09 amu

Molecular mass NH4NO3 = sum of atomic masseso Molecular mass NH4NO3 = (2 x atomic mass of N) +

(4 x atomic mass of hydrogen) + (3 x atomic mass of oxygen)

o Molecular mass NH4NO3 = (2 x 14.01 amu) + (4 x 1.008 amu) + (3 x 16.00 amu)

o Molecular mass NH4NO3 = 80.05 amu

Follow-Up Problem 2.15 p. 67 Molecular mass of H2O2 = sum of atomic masses

o Molecular mass of H2O2 = (2 x atomic mass of hydrogen) + (2 x atomic mass of oxygen)

o Molecular mass of H2O2 = (2 x 1.008 amu) + (2 x 16.00 amu)

o Molecular mass of H2O2 = 34.02 amu

Molecular mass of CsCl = sum of atomic masseso Molecular mass of CsCl = (1 x atomic mass of

cesium) + (1 x atomic mass chlorine)o Molecular mass of CsCl = (1 x 132.9 amu) + (1 x

35.45 amu)o Molecular mass of CsCl = 168.4 amu

Molecular mass of H2SO4 = sum of atomic masseso Molecular mass of H2SO4 = (2 x atomic mass of

hydrogen) + (1 x atomic mass of sulfur) + (4 x atomic mass of oxygen)

o Molecular mass of H2SO4 = (2 x 1.008 amu) + (1 x 32.07 amu) + (4 x 16.00 amu)

o Molecular mass of H2SO4 = 98.09 amu Formula mass of K2SO4 = sum of atomic masses

o Formula mass of K2SO4 = (2 x atomic mass of potassium) + (1 x atomic mass of sulfur) + (4 x atomic mass of oxygen)

o Formula mass of K2SO4 = (2 x 39.10 amu) + (1 x 32.07 amu) + (4 x 16.00 amu)

o Formula mass of K2SO4 = 174.27 amu

Sample Problem 2.16 p. 67Using Molecular Depictions to Determine Formula, Name, and Mass

(a) NaF [this is an ionic compound… both the picture and the fact that sodium is a metal and fluorine is a nonmetal makes this an ionic compound. Sodium is Na+ because sodium is in Group 1A and fluorine is F – because it is in Group 7A.] Name is sodium fluoride

Formula mass of NaF = sum of atomic masses

Formula mass of NaF = (1 x atomic mass of sodium) + (1 x mass of fluorine)

Formula mass of NaF = (1 x 22.99 amu) + (1 x 19.00 amu)

Formula mass of NaF = 41.99 amu

(b) NF3 [this is a molecule… both nitrogen and fluorine are nonmetals so you need to follow the rules for naming binary covalent compounds]

Name is nitrogen trifluoride

Molecular mass of NF3 = sum of atomic masses

Molecular mass of NF3 = (1 x atomic mass of nitrogen) + (3 x atomic mass of fluorine)

Molecular mass of NF3 = (1 x 14.01 amu) + (3 x 19.00 amu)

Molecular mass of NF3 = 71.01 amu

Follow-Up Problem 2.16 p. 68(a) Formula is Na2O [This is an ionic compound… sodium

is a metal and oxygen is a nonmetal] Name is sodium oxide

Formula mass of Na2O = sum of atomic masses

Formula mass of Na2O = (2 x atomic mass of sodium) + (1 x atomic mass of oxygen)

Formula mass of Na2O = (2 x 22.99 amu) + (1 x 16.00 amu)

Formula mass of Na2O = 61.98 amu(b) Formula is NO2 [This is a binary covalent compound…

both nitrogen and oxygen are nonmetals]Name is nitrogen dioxide

Molecular mass of NO2 = sum of atomic masses

Molecular mass of NO2 = (1 x atomic mass of nitrogen) + (2 x atomic mass of oxygen)

Molecular mass of NO2 = (1 x 14.01 amu) + (2 x 16.00 amu)

Molecular mass of NO2 = 46.01 amu

Representing Molecules with Formulas and Models

Mixtures: Classification and SeparationIn the natural world, matter usually occurs as mixtures…

Sample of clean air consists of many elements and compounds physically mixed togethero O2, N2, CO2, the noble gases [Group 8A (18)], and

water vapor Oceans are complex mixtures of dissolved ions and

covalent substances includingo Na+, Mg2+, Cl –, SO4

2-, O2, CO2, and of course H2O Rocks and soils are mixtures of numerous compounds,

including calcium carbonate, silicon dioxide, aluminum oxide, and iron (III) oxide.

Living things contain thousands of substances – carbohydrates, lipids, proteins, nucleic acids, and many simpler ionic and covalent compounds.

There are two broad classes of mixtures…

Heterogeneous mixtureso Its composition is not uniform (varies from one region

to another) Homogeneous mixtures

o Its composition is uniform (the same throughout the entire sample)

Aqueous solutions – solutions in water

Mixtures differ from compounds…

(1) The proportions of the components can vary in a mixture.

(2) The individual properties of the components of a mixture are observable.

(3) The components of a mixture can be separated by physical means.