Question

Arrange in order of atomic and ionic radii:
(a) Ni, Cu, Zn
(b) $$H^{+}$$, H, $$H^{-}$$
(c) Cr, V, Ti, Sc
(d) $$I^{+}$$, I,
(e) Cu, Ag, Au
(f) B, Be, Al, Mg

Answer 1

Hint: In order to arrange the given atoms in the increasing order of their atomic radii or ionic radii, we must know what an atomic radius is. Atomic radius of an atom is the measure of the size of the atom. In other words, we can say that it is the mean distance from the centre of the nucleus to the electron revolving in the outermost orbital.

Complete answer:
Let us first understand about the atomic radii. Atomic radius of an atom is the measure of the size of the atom. In other words, we can say that it is the mean distance from the centre of the nucleus to the electron revolving in the outermost orbital.
Now let us move to the given questions.
(a) Ni, Cu, Zn
Nickel, copper and zinc are the transition elements which belong to the d-block elements. They belong to the group IV of the periodic table. We know that the atomic radii will increase from the left to right. Therefore, the increasing order of the atomic radii of the above given elements are:
Ni < Cu < Zn.
(b) $$H^{+}$$, H, $$H^{-}$$
The atomic radius of the cation will be the smaller compared to the neutral atom size and anion size. The atomic radius of the neutral atom is smaller than the anion size. Therefore, we can write the atomic radius of the elements in the following order.
$$H^{+}$$< H < $$H^{-}$$
(c) Cr, V, Ti, Sc
For the periods, the atomic radius will first decrease and then increase, this is due to the pairing of the electrons in the d-orbitals,
Cr < V < Ti < Sc
(d) $$I^{+}$$, I, $$I^{-}$$
The atomic radius of the cation will be the smaller compared to the neutral atom size and anion size. The atomic radius of the neutral atom is smaller than the anion size. Therefore, we can write the atomic radius of the elements in the following order.
$$I^{+}$$< I < $$I^{-}$$
(e) Cu, Ag, Au
We know that the atomic radius of the elements in the periodic table will increase from the top to bottom. Therefore, we can write the order as
Cu < Ag < Au
(f) B, Be, Al, Mg
We know that the atomic radius of the element in the periodic table will increase from the top to bottom and the radius will decrease from left to right. Therefore, the order is given as
B < Al < Be < Mg

Note:
We have to remember that the atomic radius is of three types they are:
- Covalent radius
- Metallic radius
- Van Der Waals radius