Question

Why are elements Na,Mg,AI,Si,S,CI and argon in the same period?

Answer 1

Explanation:

In period the elements have same number of shells.

e.g.Na(2,8,1)

Mg(2,8,2)

Al(2,8,3)

Si(2,8,4)

S(2,8,5)

Cl(2,8,7)

Ar(2,8,8)

That's why they are in same period.

Answer 2

Answer:

In the whole of period 3, the outer electrons are in 3-level orbitals. ... That causes greater attraction between the nucleus and the electrons and so increases the ionisation energies. In fact the increasing nuclear charge also drags the outer electrons in closer to the nucleus.