Question

The minimum kinetic energy required for ionization of a hydrogen atom is $E_1$ in case electron is collided with hydrogen atom. It is $E_2$ if the hydrogen ion collided and $E_3$ when helium ion is collided. Then,

• A. $E_1=E_2=E_3$
• B. $E_1>E_2>E_3$
• C. $E_1\text{<}{E}_2\text{<}{E}_3$
• D. $E_1>E_3>E_2$

Answer 1

Answer: (C)

$E_1\text{<}{E}_2\text{<}{E}_3$

In case of hydrogen there is only $1$ proton. Hence $Z=1$

For hydrogen ion, $2$ protons, $Z=2$

For helium ion, $Z=3$

Therefore, $E=\frac{-13.6Z^2}{n^2}$

Therefore, energy required is most in $E_3>E_2>E_1$