# Help Zone

### Student Question

Secondary IV • 1yr.

In a periodic table, how do the electronegativity, atomic mass, ionization energy, and atomic radius of the elements vary?

Science

## Explanations (1)

• Explanation from Alloprof

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

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Team Alloprof • 1yr.

Hi!

First, the electronegativity of an element is the force with which its nucleus attracts electrons from its last electron shell. In the periodic table, this force increases from left to right along a period, because the elements on the right have a nucleus with more protons, therefore attracting more electrons. The force also increases from the bottom up along the families, since the lower the elements, the more their electron cloud widens and it becomes more difficult for the nucleus to keep these electrons nearby given the distance between them. .

Then the atomic mass varies increasing from left to right, as well as from top to bottom. In fact, the array is designed to follow the order of the atomic mass of its elements, since the atomic mass tracks the number of protons in an element, the atomic number, and the array is ordered according to those numbers.

As for the ionization energy, it represents the energy necessary to tear an electron from an atom. This energy is proportional to the electronegativity of an atom; if an atom has a high electronegativity, it will be difficult to remove the electrons, which will require a high ionization energy. It therefore increases from left to right, as well as from bottom to top.

Finally, the atomic radius is the distance between the nucleus of an atom and the electrons on its last electron shell. This force is inversely proportional to the electronegativity of an atom: the more a nucleus attracts its electrons, the closer they will be to the nucleus, the smaller the radius will be. So the atomic radius increases from bottom to top, and then from right to left.