Question

electron configuration and noble gas notation
match the elements below with their correct electron configuration ending.
bromine
strontium
lanthanum
4p^5 4f^1 5s^2

Explanation:

Bromine is in group 17 of the periodic table. Its electron - configuration ending is based on its position in the p - block. The outermost electrons are in the 4p orbital and it has 5 electrons in the 4p orbital, so the ending is $4p^{5}$. Strontium is in group 2, an alkaline - earth metal. It has 2 valence electrons in the 5s orbital, so the ending is $5s^{2}$. Lanthanum is a lanthanide. Its electron - configuration has a single electron in the 4f orbital, so the ending is $4f^{1}$.

Answer:

bromine - $4p^{5}$
strontium - $5s^{2}$
lanthanum - $4f^{1}$