The empirical formula is XeO₃.
<u>Explanation:</u>
Assume 100 g of the compound is present. This changes the percents to grams:
Given mass in g:
Xenon = 73.23 g
Oxygen = 26.77 g
We have to convert it to moles.
Xe = 73.23/
131.293 = 0.56 moles
O = 26.77/ 16 = 1.67 moles
Divide by the lowest value, seeking the smallest whole-number ratio:
Xe = 0.56/ 0.56 = 1
O = 1.67/ 0.56 = 2.9 ≈3
So the empirical formula is XeO₃.
Magnesium (Mg) has atomic number 12 with electronic configuration :

The valence shell of Mg is 3s which has 2 electrons as shown in above electronic configuration.
Therefore, A = 3 and B =2
Seven valence electrons .