State and explain the trend in 1st ionisation energies shown...?

Question

by the elements with the atmic numbers 2,10 and 18.

Answer 1

As you move down a family in the periodic table, the number of shells of electrons increases (draw the Bohr- Rutherford diagrams), and the atoms increase in size.

The larger the atom, the further the valence electrons are from the nucleus, and the weaker the hold it has on them. So, it becomes easier to remove a valence electron.

Since IE measures the amount of energy needed to remove an electron from an atom, this value will decrease, moving down the family from He to Rn.