What are the trends in atomic size down a group?

Atomic size increases as you move down a group in the periodic table.

In the periodic table, a group refers to a vertical column. As you move down a group, the atomic size or atomic radius increases. This is due to the addition of energy levels or shells. Each period in the periodic table corresponds to a new energy level. So, as you go down a group, the number of energy levels increases, and each additional level is further from the nucleus, making the atom larger.

The atomic size is determined by the distance between the nucleus of an atom and its outermost shell where the valence electrons are located. The more energy levels there are, the larger the distance between the nucleus and the outermost electrons, hence the larger the atomic size.

Another factor contributing to the increase in atomic size down a group is electron shielding. Electron shielding refers to the ability of inner shell electrons to shield outer shell electrons from the attractive force of the protons in the nucleus. As you move down a group, the number of inner shell electrons increases, enhancing the shielding effect. This reduces the pull of the nucleus on the outermost electrons, allowing them to move further away, which in turn increases the atomic size.

However, it's important to note that the increase in atomic size down a group is not always consistent. Other factors such as the atomic structure and the number of protons in the nucleus can also influence the atomic size. But generally, the trend is that atomic size increases as you move down a group in the periodic table.