Question

Arrange the following order in decreasing order of atomic size: Mg, Cl, Na, S, Si.

Answer 1

Hint: Generally you should know that the covalent radii are generally referred to as atomic radii. You should know that the distance is measured in picometers. Now try to recall the atomic radius patterns throughout the periodic table.

Complete step by step solution:
The atomic size decreases as we move from left to right in a period. This is because when we move along a period the nuclear charge increases which means the nucleus attracts the electrons more strongly, pulling the atom’s shell closer to the nucleus and hence the valence electrons are held closer towards the nucleus of the atom, due to which the atomic radius decreases.
Now, down the group the atomic radius increases. Here the valence electrons occupy higher levels due to increasing atomic number and here the electron shielding prevents these outer electrons from being attracted to the nucleus. Thus the resulting atomic radius is large.
Now, the decreasing order of atomic size of Mg, Cl, Na, S, Si is
Na, Mg, Si, S, Cl.

Note: To calculate the atomic radius, divide the distance between the nuclei of the atoms by two if the bond is covalent and did you know that hydrogen has the smallest atomic size because it has just one proton and no neutron.