Argon has atomic number 18 and belongs to third period and eighteenth group. Predict the group and period for the elements having atomic number 17 and 19 respectively.

Which of these belong to same group:

Which of these belong to same period:

What is the basic difference in the electronic configurations of the elements belonging to group 1 and group 17? How do these help to explain different properties of the elements?

What is metallic character? How does it change in a period?

An atom has the electronic configuration $2, 8, 7$. To which of the following element would it be chemically similar (atomic numbers are given)?

$\mathrm{N} \left(7\right), \mathrm{F} \left(9\right), \mathrm{P} \left(15\right), \mathrm{Ar} \left(18\right)$

Which has the larger atomic radius?

$\mathrm{Na}$ or $\mathrm{K}$