Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Period
1
1
1.008
Hydrogen still accounts for 90% of all known matter in the universe. One proton and one electron out there with all this space for just one poor electron to wander! (Actually there are lots of them) The isotope deuterium, which has a proton and a neutron in its nucleus, is occasionally formed over time, especially in hot stars, and the deuteriums can combine to create helium (as well as some radiation energy in those hot suns) – Helium has two protons (which fills the first “shell” so helium is inert)
2
4.0026
2
3
6.94
4
9.0122
Lithium, the first of the alkali metals (Grp 1) has one extra electron available in the second “shell”, which is why it is so reactive. And so on (keep adding deuteriums and hydrogens in the centers of really hot stars) until the second “shell” is filled – with our second noble gas (filled shell) neon. The valence can be seen to be defined by the number of electrons in the outer shell. And so forth. boron, carbon, nitrogen, oxygen, fluorine, neon…….
5
10.81
6
12.011
7
14.007
8
15.999
9
18.998
10
20.180
3
11
22.990
12
24.305
Mendeleyev first outlined these patterns in 1869 – way before anyone was aware of protons and electrons. Later, quantum theory put all these quantities (particularly the flying, zooming, orbiting electrons) onto a dual wave/particle basis. Quantum theory succeeds in making all this sub-atomic activity thoroughly predictable yet totally incomprehensible. That’s it for remembering what we are made of today.
13
26.982
14
28.085
15
30.974
16
32.06
17
35.45
18
39.948
4
19
39.098
20
40.078
21
44.956
22
47.867
23
50.942
24
51.996
25
54.938
26
55.845
27
58.933
28
58.693
29
63.546
30
65.38
31
69.723
32
72.63
33
74.922
34
78.96
35
79.904
36
83.798
5
37
85.468
38
87.62
39
88.906
40
91.224
41
92.906
42
95.96
43
[97.91]
44
101.07
45
102.91
46
106.42
47
107.87
48
112.41
49
114.82
50
118.71
51
121.76
52
127.60
53
126.90
54
131.29
6
55
132.91
56
137.33
*
71
174.97
72
178.49
73
180.95
74
183.84
75
186.21
76
190.23
77
192.22
78
195.08
79
196.97
80
200.59
81
204.38
82
207.2
83
208.98
84
[208.98]
85
[209.99]
86
[222.02]
7
87
[223.02]
88
[226.03]
**
103
[262.11]
104
[265.12]
105
[268.13]
106
[271.13]
107
[270]
108
[277.15]
109
[276.15]
110
[281.16]
111
[280.16]
112
[285.17]
113
[284.18]
114
[289.19]
115
[288.19]
116
[293]
117
[294]
118
[294]
*Lanthanoids *
57
138.91
58
140.12
59
140.91
60
144.24
61
[144.91]
62
150.36
63
151.96
64
157.25
65
158.93
66
162.50
67
164.93
68
167.26
69
168.93
70
173.05
**Actinoids **
89
[227.03]
90
232.04
91
231.04
92
238.03
93
[237.05]
94
[244.06]
95
[243.06]
96
[247.07]
97
[247.07]
98
[251.08]
99
[252.08]
100
[257.10]
101
[258.10]
102
[259.10]

The periodic table is a table of the chemical elements in which the elements are arranged by order of atomic number in such a way that the periodic properties (chemical periodicity) of the elements are made clear. The standard form of the table includes periods (usually horizontal in the periodic table) and groups (usually vertical). Elements in groups have some similar properties to each other. There is no one single or best structure for the periodic table but by whatever consensus there is, the form used here is very useful. The periodic table is a masterpiece of organised chemical information. The evolution of chemistry’s periodic table into the current form is an astonishing achievement with major contributions from many famous chemists and other eminent scientists.