Question

The ratio between radii of $H{e}^{+}$ ion and H atom is?

• A. $\frac{1}{2}$
• B. $1$
• C. $\frac{3}{2}$
• D. $2$

Answer 1

The correct option is A $\frac{1}{2}$

The electrons in 'He${}^{+}$' and 'H' is '1'. But protons in He${}^{+}$ is 2 where in 'H' is '1'. So there is nuclear attraction in He${}^{+}$ which attracts electron and reduces size. Therefore , size of He${}^{+}$ is less than that in 'H'. So $\frac{H{e}^{+}atomicsize}{Hatomicsize}$ < 1.

From the given options, it is 1/2 [ only option less than 1]