The atom having the valence-shell configuration 4s^2 4p^5 would be in what group and period?

1 Answer
Jan 4, 2017

The atom would be in Period 4 and Group 17.

Explanation:

The valence shell configuration is "4s"^2 "4p"^5.

The principal quantum number (4) gives you the Period number.

Start with H in Period 1 and count down to the fourth row (Period 4).

That brings you to "K".

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(Adapted from Chemistry - About.com)

Now, start counting to the right through the "s"-block to "Ca" ("4s"^2) and the "d"-block to "Zn".

Now that you have come to the "p"-block, count five more atoms, for a "4p"^5 configuration.

This brings you to the desired atom, "Br".

You have counted horizontally through 17 atoms, so "Br" is in Group 17.