Atomic size refers to the radius of an atom. The atomic size may be visualized as the distance between the centre of the nucleus and the outermost shell of an isolated atom.
The atomic radius of the hydrogen atom is 37 pm pm. Atomic size decreases in going from
left to right along a period.
U (3)
Be (4)
F 19)
B (5)
C(6)
N17
OB)
Elements of 2
period atomic radius
(pm)
133
89
BD
77
66
70
N (111)
Al (13)
Mg (12)
Si (14)
5 (16)
CI (171
P (15)
Elements of 3
period atomic radius
(pm)
154
136
125
117
110
104
99
Q17. (i) Identify the reason for the decrease of atomic size in the period-