cation同anion既問題

Atoms of most metals have only one or two electrons in their highest energy level. Being in the highest energy level, these electrons are relatively loosely held. Thus metals tend to lose electrons and become positively charged.

For example:A sodium atom has 11 positively charged protons and 11 negatively charged electrons, giving it a net charge of zero. If it loses an electron it has only 10 negative charges; Compare this to fluorine. Fluorine can either lose seven electrons or gain one to achieve a complete outer energy level. Tearing away seven electrons takes vast amounts of energy. Far easier to find a passing sodium atom floating around and to accept from it a loosely held electron. If sodium donates (gives the influence over) one electron to fluorine, both have full outer energy levels. And both have charge. Sodium, now +11 (protons) and -10 (electrons), has a +1 charge and is written Na+. It is an ion with a positive charge, called a cation. (Remember '+' in the middle of ca+ion. Sorry.)

Fluorine, now +9 and -10, has a -1 charge and is written F-. Negatively charged ions are called anions. As opposites attract, Na+ and F- will tend to join chemically on the basis of their opposite charges. So Na+ + F- ---> NaF.


To sum up,metals tend to lost electron and non-metal tend to gain electron because it is the simplest method for them to be stable.Since metals have less outermost shell electrons than non-metal,so it is easy for them to lose it.