Remember the periodic table of the elements. The location of each element in the periodic table is determined by its atomic number, the number of protons in the nucleus of the atom.

Hydrogen, for example, has only one proton and thus occupies the first space on the periodic table. Most of the weight of a hydrogen atom comes from its single proton, and from a neutron which may or may not be present. The surrounding electrons, in contrast, weigh very little.

Periodic Table of the Elements
1
H
2
He
3
Li		 4
Be
5
B		 6
C		 7
N		 8
O		 9
F		 10
Ne
11
Na		 12
Mg
13
Al		 14
Si		 15
P		 16
S		 17
Cl		 18
Ar
19
K		 20
Ca
21
Sc		 22
Ti		 23
V		 24
Cr		 25
Mn		 26
Fe		 27
Co		 28
Ni		 29
Cu		 30
Zn		 31
Ga		 32
Ge		 33
As		 34
Se		 35
Br		 36
Kr
37
Rb		 38
Sr
39
Y		 40
Zr		 41
Nb		 42
Mo		 43
Tc		 44
Ru		 45
Rh		 46
Pd		 47
Ag		 48
Cd		 49
In		 50
Sn		 51
Sb		 52
Te		 53
I		 54
Xe
55
Cs		 56
Ba		 71
Lu		 72
Hf		 73
Ta		 74
W		 75
Re		 76
Os		 77
Ir		 78
Pt		 79
Au		 80
Hg		 81
Tl		 82
Pb		 83
Bi		 84
Po		 85
At		 86
Rn
87
 Fr 		 88
Ra		 103
Lr		 104
Rf		 105
Db		 106
Sg		 107
Bh		 108
Hs		 109
Mt		 110
Ds		 111
Rg		 112
Uub		 113
Uut		 114
Uuq		 115
Uup		 116
Uuh		 117
Uus		 118
Uuo

The color coding for atomic numbers is described below.