The elements of the second period along with their atomic number in parentheses are given below:

CBSE Class 10 CBSE Class 10 Science
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1

(i) The elements of the second period along with their atomic number in parentheses are given below:
B (5), Be (4), 0(8), N(7), Li(3), C(6), F(9)
(a) Arrange them in the same order as they are in the periodic table.
(b) Which element has the largest and smallest atom ?
(ii) Why does the atomic radius change as we move from left to right in a period?

2

(i) (a) Li, Be, B, C, N, O, F
(b) The largest atom is Lithium and smallest is Fluorine.
(ii) The atomic radius decreases in moving from left to right along a period.
This is due to increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.