Q.What do you mean by Electron Transfer and Ion Formation?
Ans.
Positive and negative ions do not form independently. The loss and gain of electrons means the electrons must go to and come from somewhere.
Elements in the first three columns of the periodic table lose electrons until they are left with an outermost electron count of 8.
For example, as shown in the animation below, aluminum in column 3 loses 3 electrons to becomes Al3+. Since Al is losing the 3s2 3p1 electrons, its outermost electron configuration becomes 2s2 2p6 (a very stable octet). In fact, it is now like the noble gas neon.
On the other hand, elements in columns 5,6 and 7 gain electrons until they are left with an outermost electron count of 8.
For example, sulfur in column 6 gains two electrons to becomes S2-,as shown in the animation below. Since S's outermost electron configuration was already 3s2 3p4, it becomes 3s2 3p6 (a very stable octet) when it forms an ion. In fact, it is now like the noble gas argon.
In general, when forming ions, elements tend to become like noble gases in their outermost electron count, and therefore strive to achieve an octet of electrons.