JEE MAIN - Physics (2003 - No. 1)
Which of the following atoms has the lowest ionization potential ?
$${}_7^{14}N$$
$${}_{55}^{133}\,Cs$$
$${}_{18}^{40}\,Ar$$
$${}_8^{16}\,O$$
Explication
The ionisation potential increases from left to right in a period and decreases from top to bottom in a group. Therefore ceasium will have the lowest ionisation potential.