Answer
$NaBr$
Work Step by Step
In order to determine the ratio in which two elements combine, you must find the ionic charge of each element. The positive and negative charges will balance in the ionic compound.
Na is in the first column. This means it's ion has a +1 charge.
Br is in the second to last column. This means it's ion has a -1 charge.
Na and Br will therefore combine in a 1:1 ratio.
