(1) The element with a valence electron configuration of 3s23p2 is in group and period (2) The element with a valence electron configuration of 4s24p1 is in group and period .

Answer 1

Since the valence shell is n = 3 it is in Period 3. Since there are 4 valence electrons (2 in 3s and 2 in 3p) it is in Group 4A (14).

For 4s2 4p1, the valence shell in n = 4 so this is in Period 4 and there are 3 valence electrons putting it in group 3A (13)

Answer 2

If you take a look at a periodic table that shows orbitals¹ you can see what elements have which configurations. An element with the valence shell configuration 3s²3p² has a full s-orbital (because s-orbitals can hold at most two electrons) and two electrons in the p-orbitals. The table linked below shows which row (or period) on the table has elements with valence 3p orbitals. Because there are two electrons in the p-orbital, the column (or group) that this element is in will be the second in the 3p row.

The element in the second column of the p-orbitals and third row would be silicon (Si). It's not shown in the linked table, but the group that this element is in is shown at the top of the table; it's also just the number of the column counting from left to right. So silicon is in the third row and fourteenth column, or third period and fourteenth group.

The same exact logic goes to find that Gallium is in the fourth period and the thirteenth group.

1. Periodic table with orbitals: https://files.mtstatic.com/site_4334/1281/0?Expires=1596469161&Signature=jjTVR8VgBL~vr6R~WYF14I~9v7WsySEwDDu0lCc9Gs-rzTKG4TEvqk6ZBOfQip6tCF-QQFUpPmHkr8qY7A~6wjjSGkmpDV-zNZneYgqdj0hEwOZFYQGBr6dVtZtl37QIu9dFI2zfSxYnYqiptYckI1rQ4ZaE8g00-oHJtSIJk1k_&Key-Pair-Id=APKAJ5Y6AV4GI7A555NA

Answer 3

This video uses the periodic table to give you a really helpful visual understanding of how orbital notation works. I hope this helps. :)