Question

Which atoms are listed in order of increasing size (smallest to largest)?

	a.	C < N < O < F
	b.	N < O < P < Si
	c.	Mg < Ca < K < Rb
	d.	Cl < S < O < F

Answer 1

a)

C, N, O and F are in same period

Size decreases as we move from left to right in a period

So, size order is:

C > N > O > F

a is wrong

b)

P and Si are in period 3.

N and O are in period 2

So, P and Si are larger than N and O

Between N and O, O should be smaller as O lies to the right of N

So, b is wrong

c)

Mg should be smallest as this is in period 3

Rb should be smallest as this is in period 5

Both Ca and K are in period 4

Ca is smaller than K because Ca is to the right of K in periodic table

c is correct

d)

F is in period 2 and hence should be smaller than Cl and S.

Answer: c