The element with electronic configuration $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^3$ belongs to which group and period?

**Period** equals the highest principal quantum number, which is 4 here. So Period 4. **Group**: the outermost shell ($n=4$) has $4s^2 4p^3$. For p-block elements, group number = 10 + (number of $s$ valence + number of $p$ valence) = 10 + (2 + 3) = **15**. This configuration matches **arsenic (As)**, atomic number 33. Check: As is below P and N in group 15 (nitrogen family), period 4. ✓