Question

The correct order of the atomic radii of C, Cs, Al and S is:
(a) $S$ < $C$ < $Al$ < $Cs$
(b) $S$ < $C$ < $Cs$ < $Al$
(c) $C$ < $S$ < $Cs$ < $Al$
(d)$C$ < $S$ < $Al$ < $Cs$

Answer 1

Hint: As we move from left to right, atomic radii decreases and as we move from top to bottom, the atomic radii increases, so identify the positions of these elements in the periodic table and then, you can easily find the increasing order of atomic radii in these elements.

Complete answer:
First of all, let's discuss what an atomic radius is. By the term atomic radius, we mean the average distance of the outermost shell from the nucleus.
The atomic decreases as we move from right to left of the periodic table and increases as we move from top to bottom of the periodic table.
The increasing order of the atomic radii of the elements C, Cs, Al and S can be easily determined with the help of the periodic table as:

1 H

2 He

3Li

4Be

5 B

6 C

7 N

8 O

9 F

10 Ne

11Na

12Mg

13 Al

14 Si

15 P

16 S

17 Cl

18 Ar

19K

20Ca

21Sc

22Ti

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

37Rb

38Sr

39Y

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

55Cs

56Ba

57La

72 Hf

73 Ta

74 W

75 Re

76 Os

77Ir

78 Pt

79 Au

80 Hg

81 Tl

82 Pb

83 Bi

84 Po

85 At

86 Rn

From the periodic table , we can see that the Cs( cesium) has the largest atomic radii among all, followed by aluminum; Al then carbon; C and Sulphur; S has the smallest atomic radii of all. So, the increasing order of atomic radii is;
$S$ < $C$ < $Al$ < $Cs$

Hence, option(a) is correct.

Note:
Atomic radii s divided into three types;
1. Covalent radius : the distance between the two atoms when they are bound by a single bond in a covalent molecule is called the covalent radius.
2. Van Der Waals radius: the one half the distance between the nuclei of the two non covalently bonded atoms is called the Van Der Waals radius.
3. Metallic radius: it is one half the internuclear distance between the two adjacent metal atoms.