Answer
Helium- gain 0 - lose 0
Oxygen- gain 2 - lose 6
Carbon- gain 4 - lose 4
Sodium- gain 7 - lose 1
Chlorine- gain 1 - lose 7
Work Step by Step
Helium has two electrons in its outer shell, meaning it already has a complete outer shell.
Oxygen has 6 electrons in its outer shell. In order to gain a complete outer shell it must either lose 4 electrons, removing its second electron shell entirely, or gain 2 electrons in order to max out its second shell with a total of 8.
Carbon has 4 electrons in its second shell of electrons. it must either lose 4 electrons, removing its second shell entirely, or gain 4 electrons in order to max out its second shell with a total of 8.
Sodium has 1 electron in its third energy level. it must either lose 1 electron which will remove its third energy level entirely, or gain 7 electrons which will max out its third electron shell with a total of 8.
Chlorine has 7 electrons in its third energy level. It must either lose 7 electrons which will remove its third energy level entirely, or gain 1 electron which will max out its third electron shell with a total of 8.
