Download Atoms, Molecules and Ions Atomic Theory of Matter

Atoms, Molecules and Ions
John Dalton 1806
Atomic Theory of Matter
1. Matter consists of indivisible atoms
2. All atoms of a given element
have identical properties
3. Different elements have atoms that
differ in mass
4. Atoms are indestructible and chemical
reactions are a rearrangement of atoms
5. Compounds contain a definite and small number
of atoms
1. Matter consists of indivisible atoms
subatomic particles
1. electrons
2. protons
3. neutrons
electrons
charge = -1.60 x 10-19 C = -1
mass = 9.1 x 10-31 kg
protons
charge = +1
mass = 1.673 x 10-27 kg
neutrons
charge = 0
mass = 1.675 x 10-27 kg
1. Matter consists of indivisible atoms
nucleus = protons + neutrons
electrons move around the nucleus
electron “cloud” = volume of atom
average diameter of atom 10-10 m = ångström (Å)
2. All atoms of a given element
have identical properties ? not exactly
A
ZX
atoms of an element = same number of protons
atomic number = Z
Z = 6 = C carbon
Z = 30 = Zn zinc
6C
30Zn
6 e30 e-
elements neutral # protons = # eelements different # neutrons
proton + neutron = A = mass number
2. All atoms of a given element
have identical properties
element can have isotopes
carbon Z = 6
A
ZX
7 nuclides of C
12 C
6
most abundant 6 neutrons
Carbon-14 dating
6 protons + 8 neutrons
14 C
6
What is the symbol for a nuclide that contains
22 neutrons and 18 protons?
40
18 Ar
4. Atoms are indestructible and chemical
reactions are a rearrangement of atoms
reactions involve valence electrons
valence e- = Group number
1
8
2
3 4 5 6 7
1
8
2
3 4 5 6 7
non-metals
metals
elements arranged by atomic number
column
group
chemical properties
row
period
are determined by an
element’s group
Noble gases
unreactive
8 valence electrons (He 2 valence e-)
monatomic gases
Alkali metals
soft solids
very, very reactive
1 valence electron
lose 1 electron
+
Na ( 11 protons, 10 e-)
Na (11 protons, 11 e )
cation
Alkaline earth metals
solids
reactive
2 valence electrons
Sr
Sr2+
7
lose 2 electrons
Halogens
very reactive
7 valence electrons
Cl (17 protons, 17
e -)
gain 1 electron
-
Cl (17 protons, 18 e-)
anion
Properties of Metals
Good conductors of heat and electricity
Solids
Lose e- to form cations
Properties of Non-metals
Poor conductors of heat and electricity
Solids, liquids and gases
5
3 4
B
C
N
Gain e- to form anions
5
6
Si
14
P
6
7
7
O
15
S 16
Cl 17
Se34
Br35
Te52
I 53
As33
= metalloids
8
F
9
At85
H1
doesn’t fit anywhere
lose eH (1 proton, 1 e-)
gain eH (1 proton, 1 e-)
+
H (1 proton, 0 e-)
proton
H (1 proton, 2 e-)
hydride
5. Compounds contain a definite and small number of atoms
Ionic solids include a metal and a non-metal
cation + anion Æ neutral molecule
+
sodium + chlorine
Na+
Cl -
NaCl
sodium chloride
lithium + oxygen
2Li +
O
Li 2 O
lithium oxide
magnesium + nitrogen
Mg 3 N2 magnesium nitride
Mg 2+
N3strong interactions (ion-ion) Æ high melting points
(801o C for NaCl; >1700o C for Li2O)
Transition metals
more than 1 form except Ag+, Zn2+, Cd2+, Al3+
aluminum+ sulfur
Al3+
S2Al2 S 3
aluminum sulfide
manganese + oxygen
Mn1+ Mn2+ Mn3+ Mn4+
Mn4+ O2MnO2
manganese(IV) oxide
Covalent compounds
non-metal + non-metal
share valence electrons = chemical bonds
carbon + chlorine
1 mono
4+
Cl
C
2 di
3 tri
CCl4
4 tetra
carbon tetrachloride
5 penta
nitrogen + oxygen
?
N
O 2(2+) NO nitrogen monoxide
(4+) NO2 nitrogen dioxide
(4+) N2O4 dinitrogen tetroxide
6
7
8
hexa
hepta
octa
More covalent compounds
N 3+ H1-
NH3
nitrogen trihydride
ammonia
H 1+ O2-
H2O
dihydrogen monoxide
water
weak forces Æ low m.p.
(0.0o C for water)
Table 2.5 p. 62 Polyatomic ions
NH4+
OHNO3SO42PO43-
ammonium
hydroxide
nitrate
sulfate
phosphate
ClO3MnO4CrO42CO32-
chlorate
permanganate
chromate
carbonate