Question

My textbook says that this happens because the number of protons, and thus the total positive charge, increases - a greater attractive force acts on each electron. The book says that this is despite the fact that the number of electrons increases, as each new electron is added to the outermost shell and so the increase in the repulsive force between electrons (electron shielding) is small. But I do not see how this justifies the increase in the force per electron despite the increase in electrons. Help!

Answer 1

The increase in the force per electron despite the increase in electrons can be explained by the concept of electron shielding and effective nuclear charge. Electron shielding refers to the blocking of the attractive force between the nucleus and an electron by other electrons in the atom. Core electrons are more effective at shielding than valence electrons.

Step-by-step explanation:

The increase in the force per electron despite the increase in electrons can be explained by the concept of electron shielding and effective nuclear charge. Electron shielding refers to the blocking of the attractive force between the nucleus and an electron by other electrons in the atom. Core electrons are more effective at shielding than valence electrons. Therefore, although the number of electrons increases, the increase in repulsive force between electrons is small. On the other hand, the effective nuclear charge experienced by the electrons increases as we move from left to right across a period because the attractive force between the protons in the nucleus and the electrons is stronger. As a result, the electrons are drawn closer to the nucleus, making the atom smaller.