Question

in what period is argon? in what group?
period =
group =

Explanation:

Argon (Ar) has an atomic number of 18. In the periodic table, the period number corresponds to the number of electron shells. Argon has 3 electron shells, so it's in period 3. The group number for noble gases (argon is a noble gas) is 18 (or 8A in some notations, but the modern group numbering for noble gases is 18).

Answer:

Period = 3
Group = 18