Question

The pair that has similar atomic radii is:
(a) Sc and Ni
(b) Ti and Hf
(c) Mo and W
(d) Mn and Re

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 step by step 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.
We can easily find the pair which has the same atomic radii 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

87Fr

88Ra

89Ac

104 Rf

105 Db

106 Sg

107 Bh

108 Hs

109 Mt

110 Ds

111 Rg

112 Cn

113 Uut

114 Uuq

115 Uup

116 Uuh

117 Uus

118 Uuo

57 La

58 Ce

59 Pr

60 Nd

61 Pm

62 Sm

63 Eu

64 Gd

65 Tb

66 Dy

67 Ho

68 Er

69 Tm

70 Yb

71 Lu

89 Ac

90 Th

91 Pa

92 U

93 Np

94 Pu

95 Am

96 Cm

97 Bk

98 Cf

99 Es

100 Fm

101 Md

102 No

103 Lr

From the periodic table , we can see that the Sc has a larger radius than the Ni, Ti has smaller radii than Hf , Mo and W have almost similar radii as they lie next to each other while we move down the group and Re has larger radii than Mn.
So, Mo and W have almost similar radii.
So, the correct answer is “Option C”.

Note: Atomic radii is 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.