To draw the Lewis dot structure for xenon dibromide (XeBr2), we start by determining the total number of valence electrons available. Xenon, a noble gas in group 8A, contributes 8 valence electrons, while each bromine atom, from group 7A, contributes 7 valence electrons. With two bromine atoms, the total valence electrons sum up to 22 (8 from xenon + 7 × 2 from bromine).
In the Lewis structure, xenon is placed at the center, bonded to the two bromine atoms. To satisfy the octet rule for the surrounding bromine atoms, we distribute electrons around them. Each bromine will have three lone pairs (6 electrons) and one bond (2 electrons), totaling 8 electrons for each bromine. This arrangement uses up 16 of the 22 available valence electrons.
With 6 electrons remaining, we place these around the xenon atom as three lone pairs. This results in xenon having a total of 10 electrons (2 from each bond with bromine and 6 from the lone pairs). Although this configuration breaks the octet rule, it is permissible for xenon, as it can accommodate more than 8 electrons due to its position in the periodic table. In fact, xenon can ideally hold up to 12 or even 16 electrons in certain compounds, but in this case, it is stable with 10 electrons.
Thus, the Lewis dot structure for xenon dibromide illustrates xenon at the center with two bromine atoms bonded to it, each surrounded by three lone pairs, demonstrating that central atoms like xenon can exceed the octet rule while remaining stable.