Which of the following represents alkali metals (i.e. 1 group metals) based on $(IE{)}_1$ and $(IE{)}_2$ values?

The correct option is C

Z = 195; 500

Recollect the periodic table.

Where are the alkali metals placed?

Yeah, you are right.

Group 1.

This means that if we remove an electron from an alkali metal it will become more stable because it will be in the noble gas configuration.

So, removing the first electron will be easy. So, $I{E}_1$ will be low.

But, to remove the second electron from an alkali metal we have to provide a lot more energy because it is very stable.

So, what are we looking for in the data? There should be large difference between $I{E}_1$ and $I{E}_2$.

X = $(IE{)}_1$ $\to$ 100; $(IE{)}_2$ $\to$ 110 (False)

Y = $(IE{)}_1$ $\to$ 95; $(IE{)}_2$ $\to$ 120 (False)

Z = $(IE{)}_1$ $\to$ 195; $(IE{)}_2$ $\to$ 500 (True)

M = $(IE{)}_1$ $\to$ 200; $(IE{)}_2$ $\to$ 250 (False)

Therefore, Z is following the characteristics of alkali metals.