Answer
Al : It will lose 3 electrons to attain stable configuration
Sn : It will lose 4 electrons to attain stable configuration
Br : It will gain 1 electron to attain stable configuration
Se : It will gain 2 electrons to attain stable configuration
Work Step by Step
The number of valence electrons is determined by the group number of the element.
Al : 3 (Group 13 : valence electrons = 13 -10 = 3) - It will lose 3 electrons to attain stable configuration
Sn : 4 (Group 14 : valence electrons = 14 -10 = 4) - It will lose 4 electrons to attain stable configuration
Br : 7 (Group : valence electrons = 17 -10 = 7) - It will gain 1 electron to attain stable configuration
Se : 6 (Group 16 : valence electrons = 16 -10 = 6) - It will gain 2 electrons to attain stable configuration
