Question

PLEASE HELP! QUICK!!
Why and how does the size of the atom decrease on moving along a period?

Answer 1

The size of an atom decreases across a period due to the increase of protons and electrons, but no extra shielding (shielding stays the same).

This means that there will be a greater nuclear attraction between the nucleus (protons in the nucleus) and the outer electrons, which basically pulls the outer shells in towards the nucleus, making the nuclear radii smaller. The more protons and electrons added, the greater the nuclear attraction is, making the outer shells get pulled in more.

This only applies to periods however, purely due to the fact that the shielding stays the same, so nuclear attraction is not affected by the 'protection' of the shells in the atom.

I hope this helps :)

Answer 2

THANKYOU VERY MUCH!!