Explain the variation of atomic radius along a period and along a group of the Periodic Table

The atomic radius is mostly influenced by the electron cloud and its interaction with the nucleus.Along a period, the atomic number increases, which indicates that the number of electrons also increases, given that an atom is a neutral species. However, the added electrons remain in the same orbital. At the same time, the number of protons increases, increasing the nucleus-electron cloud attraction. This overpowers the increment in electrons, so the atomic radius decreases.Along a group, however, the electrons are added to a new, more peripheral orbital. As such, this growth in volume is not compensated by the nucleus-electron cloud attraction, even though the number of protons is increasing. Thus, the radius increases.