Metals are elements that give off “free” electrons. Metals generally have anywhere between 1 to 3 electrons excess of a closed shell. Non-metals on the other hand have similar number of electrons in deficit of the numbers required for a closed shell.
Element | Symbol | Atomic Number | Electronic Configuration |
Sodium | Na | 11 | 1s 2 2s 2 2p 6 3s 1 |
Aluminium | Al | 13 | 1s 2 2s 2 2p 6 3s 2 3p 1 |
Calcium | Ca | 20 | 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 |
Element | Symbol | Atomic Number | Electronic Configuration |
Carbon | C | 6 | 1s 2 2s 2 2p |
Oxygen | O | 8 | 1s 2 2s 2 2p 4 |
Chlorine | Cl | 17 | 1s 2 2s 2 2p 6 3s 2 |
It is clear from these tables that to complete a given orbit, metals give off electrons and become positive ions. Non-metals accept electrons and become negative ions. Hydrogen (H) and Helium (He) are two light elements which are non-metallic in nature. Hydrogen lacks one electron to complete its one and only one shell. Helium has 2 electrons in its only orbit.The metals are placed on the left side and the centre of the periodic table. The non-metals are placed on the right side of the periodic table. Hydrogen is the only non-metal that is placed on the left-hand side of the periodic table. The reason for this is that the electronic configuration of H is 1s1, same as the Group I A elements or the alkali elements such as Na, and K. The middle portion of the periodic table consists of elements that are called transition metals elements. These elements are metallic in nature but not as metallic as alkali (Na, K, Cs etc) or alkaline earth metals (Mg, Ca etc.)