write the electron configuration for a neutral atom of bromine.

Explanation:

Step1: Determine bromine's atomic number

Bromine (Br) has an atomic number of 35. This means a neutral bromine atom has 35 electrons.

Step2: Fill electron - subshells

We fill the subshells according to the Aufbau principle (1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p etc.). 1s can hold 2 electrons: $1s^{2}$ 2s can hold 2 electrons: $2s^{2}$ 2p can hold 6 electrons: $2p^{6}$ 3s can hold 2 electrons: $3s^{2}$ 3p can hold 6 electrons: $3p^{6}$ 4s can hold 2 electrons: $4s^{2}$ 3d can hold 10 electrons: $3d^{10}$ 4p needs to hold the remaining electrons. We have used $2 + 2+6 + 2+6 + 2+10=30$ electrons so far. So 4p holds $35 - 30 = 5$ electrons: $4p^{5}$

Answer:

$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}$