Valence configuration and the periodic table

As described earlier the first element in each row of the periodic table has its outer electron in a shell with a number corresponding to the number of the row. In electron configurations the number of the row is given the symbol n.

The elements in the first row of the periodic table (H and He) have n equal to one, and the electron configuration for H is 1s¹ and for He is 1s².

For a variety of reasons these elements do not fit well into the block structure of the periodic table.
For example, these elements are nonmetals and have quite different properties to s-block elements which are metals.

The diagram showing how valence configuration can be written from the possition of the element in the periodic table begins with row 2 of the periodic table. This diagram shows that each group has a characteristic configuration with the same number of outer electrons in the same types of subshells.

s-block
ns^x
x < 2

valence configuration for rows 2 - 6
of the periodic table

p-block
——— ns² np^x ———
x < 6

ns¹

ns²

np¹

np²

np³

np⁴

np⁵

np⁶

3
Li

4
Be

5
B

6
C

7
N

8
O

9
F

10
Ne

11
Na

12
Mg

d-block
ns² (n-1)d^x (x < 10)

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

The difference between the elements in the groups is that the valence electrons occupy different shells with the number of the shell (given by n).
The number n of the shell which the valence electrons occupy is the same as the period number for s and p block elements.

Examples:

Valence configuration for potassium: 4s¹
Valence configuration for phosphorus: 3s² 3p³
Valence configuration for lithium: 2s¹