Question

The energy of electron in first energy level is - 21.79 ×10⁻¹²
erg per atom. The energy of electron in second energy level
is :
(a) -54.47×10⁻¹² erg atom⁻¹
(b) -5.447×10⁻¹² erg atom⁻¹
(c) -0.5447×10⁻¹²2 erg atom⁻¹
(d) -0.05447×10⁻¹² erg atom⁻¹

Answer 1

The energy of electron in second energy level

is :

(b) -5.447×10⁻¹² erg atom⁻¹

1. The energy of electron in different Bohr's energy levels is given by the equation,

E =-21.79 ×10⁻¹² x(1/n^2) erg atom⁻¹ where n is the principal quantum number.

2. In this case, we have n = 2.

3. Thus, E= -21.79 ×10⁻¹² x(1/2^2)

= -21.79 ×10⁻¹² x(1/4)

= -5.447×10⁻¹² erg atom⁻¹

4. Thus, (b) is the correct answer.

Answer 2

The energy of electron in second energy level is (b) -5.447×10⁻¹² erg atom⁻¹.

• The energy is expressed here as the work that is required to remove the electron indefinitely.
• The electron's energy in infinity is taken as zero.
• The electron at infinity is free from the proton's effect. When the electron becomes attracted to the proton, the interaction evolves, and thus electron's energy decreases and becomes negative.
• If n=1, then the electron's energy in the H atom is - 21.79 ×10⁻¹². The minus sign denotes the moving away of the electron from the proton