M13 The first 20 elements

Aim: To present the first twenty elements of the Periodic Table using the Rutherford-Bohr model.


  The comments that were made about atomic dimensions in connection with illustrations M11 and M12 are also valid here.
Atomic radius decreases with increasing atomic number. In any period (row) of the periodic table the atoms on the right -hand side are smaller than those on the lefthand side. This is apparent from the atomic radii for the elements of the third period given below,which are expressed in pm (picometres): (picometer = 10-12 m)


With the exception of helium, the s-electrons which form electron pairs in the ground state are represented as unpaired so that chemical bonding can be explained simply.