Answer:
Lithium develops a positive charge because it has one valence electron. Instead of lithium trying to steal 7 electrons from other elements to obtain an octet, it is easier to lose its one electron to become stable. Because neutral atoms contain the same amount of protons and electrons, when lithium loses one electron, there is one more proton than electrons.
In other words
Lithium has 3 protons and 3 electrons in its neutral state, but it loses one electron to become stable so it now has 3 protons and 2 electrons, and there is one more proton than electrons: +3 -2 = +1 charge
Step-by-step explanation: