Atoms, Molecules and Ions1806Atomic Theory of Matter

1. Matter consists of indivisible atoms

2. All atoms of a given element have identical properties3. Different elements have atoms that differ in mass4. Atoms are indestructible and chemical reactions are a rearrangement of atoms5. Compounds contain a definite and small number of atoms

John Dalton

1. Matter consists of indivisible atoms

subatomic particles 1. electrons2. protons3. neutrons

electrons charge = -1.60 x 10-19 C = -1mass = 9.1 x 10-31 kg

protons charge = +1mass = 1.673 x 10-27 kg

neutrons charge = 0mass = 1.675 x 10-27 kg

1. Matter consists of indivisible atoms

nucleus = protons + neutrons

electrons move around the nucleuselectron “cloud” = volume of atom

average diameter of atom 10-10 m = ångström (Å)

2. All atoms of a given element have identical properties

atoms of an element = same number of protonsatomic number = Z

XZ

elements neutral # e- # protons =

elements different # neutronsproton + neutron = A = mass number

A

Z = 6 carbon= CZ = 30 = Zn zinc

6C30Zn

6 e-

30 e-

? not exactly

element can have isotopes 7 nuclides of Ccarbon Z = 6

6Cmost abundant 6 neutrons

12

Carbon-14 dating C6

14

6 protons + neutrons

What is the symbol for a nuclide that contains22 neutrons and 18 protons?

Ar1840

2. All atoms of a given element have identical properties

XZA

8

4. Atoms are indestructible and chemical reactions are a rearrangement of atoms

valence electronsreactionsvalence e- = Group number

12 3 4 5 6 7

8

12 3 4 5 6 7

8

elements arranged by atomic numbercolumn grouprow period

chemical properties

Noble gasesunreactive

monatomic gases

8 valence electrons

Alkali metalssoft solidsvery, very reactive1 valence electron lose 1 electron

Na( protons, e-)1111 Na ( protons, e-)11 10+

cation

(He 2 valence e-)

Alkaline earth metalssolidsreactive2 valence electrons lose 2 electrons

Sr Sr2+

metals non-metals

conduct heat, solids (Hg)

electricity

lose e-

Non-metals

Si 14

C 6B 5 N 7 O 8 F 9

P 15 S 16 Cl 17

As33 Se34 Br35

Te52 I 53

At85

3 4 5 6 7

= metalloids

poor conductorssolids, liquids, gases

Group 7 halogens X2

very reactive7 valence electrons gain 1 electron

Cl ( protons, e-)17 17 Cl ( protons, e-)17 18-

anion

non-metals gain electrons

H 1 doesn’t fit anywherelose e-

H ( proton, e-)1 1 H ( proton, e-)1 0+

protonH ( proton, e-)1 1 H ( proton, e-)1 2-

hydride

gain e-

5. Compounds contain a definite and small number of atoms Ionic solids

cation + anion+ -

metal non-metal

lithium oxygenLi O+ 2-

+Li O lithium oxide

magnesium nitrogen+Mg N2+ 3- Mg N magnesium nitride

3 2

strong interactions (ion-ion)

sodium chlorineNa Cl+ -

+NaCl sodium chloride

2

high melting points

801o C

> 1700oC

Transition metals

more than 1 form except Ag+

Zn2+

Cd2+

Al3+

aluminum+sulfurAl3+ S2-

Al S2 3aluminum sulfide

manganese oxygen+Mn1+ Mn2+ Mn3+ Mn4+

Mn4+ O2- MnO2

manganese(IV) oxide Mn3+ Mn2O3

manganese(III) oxide

O2-

Covalent compounds

share valence electrons = chemical bondscarbon + chlorine

C Cl -4+

CCl4

carbon chloridetetra

1 mono2 di3 tri4 tetra5 penta6 hexa7 hepta8 octa

nitrogen + oxygenN O 2-?

NO nitrogen monoxide 2+

NO2 nitrogen dioxide 4+

N2O4 dinitrogen 4+

non-metal + non-metal

tetroxide

Covalent compounds

H

N H1-3+ NH3 nitrogen trihydride ammonia

O2-1+ H2O dihydrogen monoxide water

weak forces low m.p. 0.0oC

Polyatomic ions

NH4+ ClO3

-

Table 2.5 p. 62

ammoniumOH- hydroxideNO3

- nitrateSO4

2- sulfatePO4

3- phosphate

chlorateMnO4

- permanganateCrO4

2- chromateCO3

2-carbonate