Look at the following two examples of how to use the periodic table to work out chemical formulae for ionic compounds:
1+ 2+
Hydrogen 1
H 1
Lithium 7
Li 3 3 4 5 6 7
Sodium 23
Na 11
Potassium 39
K 19
Rubidium 85
Rb 37
Caesium 133
55
Cs 223
Francium 87
Fr
Beryllium 9
Be 4
Magnesium 24
Mg 12
Calcium 40
Ca 20
Strontium 88
Sr 38
Barium 137
Ba 56
Radium 226
Ra 88
Scandium 45
Sc 21
Yttrium 89
Y 39
Lanthanum 139
La 57 Ac *
Actinium 227
89 =
Titanium 48
Ti 22
Zirconium 91
Zr 40
Hafnium 178
Hf 72
Rutherfordium 104
Rf
Vanadium 51
V 23
Niobium 93
Nb 41
Tantalum 181
Ta 73
dubnium 105
Db
Chromium 52
Cr 24
Molybdenum 96
Mo 42
Tungsten 184
W 74
Seaborgium 106
Sg
Manganese 55
Mn 25
Technetium 99
Tc 43
Rhenium 186
Re 75
Bohrium 107
Bh 26
Ruthenium 101
Ru 44
Osmium 190
Os 76
Hassium 108
Hs Fe
Iron 56
Cobalt 59
Co 27
Rhodium 103
Rh 45
Iridium 192
Ir 77
Meitnerium 109
Mt
Nickel 59
Ni 28
Palladium 106
Pd 46
Platinum 195
Pt 78
Darmstadtium 110
Ds
Copper 64
Cu 29 Ag
Silver 108
47 Au
Gold 197
79
Roentgenium 111
Rg Zn
Zinc 65
30
Cadmium 112
Cd 48
Mercuy 201
Hg 80
Copernicium 112
Cn 5
Aluminium 27
Al 13
Callium 70
Ga 31
Indium 115
In 49
Thallium 204
Tl 81
Ununtrium 113
Uut
Boron 11
B 6
Silicon 28
Si 14
Germanium 73
Ge 32 Sn
Tin 119
50 Pb
Lead 207
82
flerovium 114
Fl
Carbon 12
C
Nitrogen 14
N 7
Phosphorous 31
P 15
Arsenic 75
As 33
Antimony 122
Sb 51
Bismuth 209
Bi 83
Ununpentium 115
Uup 8
Sulfur 32
S 16
Selenium 79
Se 34
Tellurium 128
52
Te 210
Polonium 84
Po
Livermorium 116
Lv
Oxygen 16
O
Fluorine 19
F 9
Chlorine 35-5
Cl 17
Bromine 80
Br 35
Iodine 127
I 53 210 Astatine At 85
Ununseptium 117
Uus 2 Ne
Neon 20
10
Argon 40
Ar 18
Krypton 84
Kr 36
Xenon 131
54
Xe 222
Radon Rn 86
Ununoctium 118
Uuo 3+ 4– 3– 2– 1– 0
Helium 4
He
K+
I–
: Fig. 19.8 How to use the periodic table to work out the formula of potassium iodide (KI)
1+ 2+
Hydrogen 1
H 1
Lithium 7
Li 3 3 4 5 6 7
Sodium 23
Na 11
Potassium 39
K 19
Rubidium 85
Rb 37
Caesium 133
55
Cs 223
Francium 87
Fr
Beryllium 9
Be 4
Magnesium 24
Mg 12
Calcium 40
Ca 20
Strontium 88
Sr 38
Barium 137
Ba 56
Radium 226
Ra 88
Scandium 45
Sc 21
Yttrium 89
Y 39
Lanthanum 139
La 57 Ac *
Actinium 227
89 =
Titanium 48
Ti 22
Zirconium 91
Zr 40
Hafnium 178
Hf 72
Rutherfordium 104
Rf
Vanadium 51
V 23
Niobium 93
Nb 41
Tantalum 181
Ta 73
dubnium 105
Db
Chromium 52
Cr 24
Molybdenum 96
Mo 42
Tungsten 184
W 74
Seaborgium 106
Sg
Manganese 55
Mn 25
Technetium 99
Tc 43
Rhenium 186
Re 75
Bohrium 107
Bh 26
Ruthenium 101
Ru 44
Osmium 190
Os 76
Hassium 108
Hs Fe
Iron 56
Cobalt 59
Co 27
Rhodium 103
Rh 45
Iridium 192
Ir 77
Meitnerium 109
Mt
Nickel 59
Ni 28
Palladium 106
Pd 46
Platinum 195
Pt 78
Darmstadtium 110
Ds
Copper 64
Cu 29 Ag
Silver 108
47 Au
Gold 197
79
Roentgenium 111
Rg Zn
Zinc 65
30
Cadmium 112
Cd 48
Mercuy 201
Hg 80
Copernicium 112
Cn 5
Aluminium 27
Al 13
Callium 70
Ga 31
Indium 115
In 49
Thallium 204
Tl 81
Ununtrium 113
Uut
Boron 11
B 6
Silicon 28
Si 14
Germanium 73
Ge 32 Sn
Tin 119
50 Pb
Lead 207
82
flerovium 114
Fl
Carbon 12
C
Nitrogen 14
N 7
Phosphorous 31
P 15
Arsenic 75
As 33
Antimony 122
Sb 51
Bismuth 209
Bi 83
Ununpentium 115
Uup 8
Sulfur 32
S 16
Selenium 79
Se 34
Tellurium 128
52
Te 210
Polonium 84
Po
Livermorium 116
Lv
Oxygen 16
O
Fluorine 19
F 9
Chlorine 35-5
Cl 17
Bromine 80
Br 35
Iodine 127
I 53 210 Astatine At 85
Ununseptium 117
Uus 2 Ne
Neon 20
10
Argon 40
Ar 18
Krypton 84
Kr 36
Xenon 131
54
Xe 222
Radon Rn 86
Ununoctium 118
Uuo
KI 3+ 4– 3– 2– 1– 0
Helium 4
He
Mg2+
I–
: Fig. 19.9 How to use the periodic table to work out the formula of magnesium iodide (MgI2
)
Mgl2
CONCENTRATE! The criss-cross method can help you write the formulae of chemical compounds. Using this method, the charge of the ions on the two atoms cross over and become the subscript of the other ion.
Mg+2
) Fig. 19.10 Criss- cross method for magnesium iodide