Answer: A. [tex]MgBr_2[/tex]
Explanation: Ionic bonds are formed by transfer of electrons between metal and non metals.
Electronic configuration of magnesium:
[tex][Mg]:12:1s^22s^22p^63s^2[/tex]
Magnesium atom will lose two electron to gain noble gas configuration and form magnesium cation with +2 charge.
[tex][Mg^{2+}]:10:1s^22s^22p^6[/tex]
Electronic configuration of bromine:
[tex][Br]:35:1s^22s^22p^63s^23p^64s^23d^{10}4p^5[/tex]
Bromine atom will gain one electron to gain noble gas configuration and form bromide ion with -1 charge.
[tex][Br^-]:361s^22s^22p^63s^23p^64s^23d^{10}4p^6[/tex]
In magnesium bromide, two electrons from metal gets transferred to bromine atom and thus form an ionic bond to give [tex]MgBr_2[/tex]
