Define atomic size. Give its unit of measurement. In the Modern Periodic Table what trend is observed in the atomic radius in a group and a period and why is it so ?

Define atomic size. Give its unit of measurement. In the Modern Period

1.	Define atomic size. Give its unit of measurement. In the Modern Periodic Table what trend is observed in the atomic radius in a group and a period and why is it so ?
Answer» Solution :• Atomic SIZE is defined as the distance between the centre of nucleus and the outermost SHELL of an ISOLATED atom. • Atomic radius increases down the group. This is because new shells are being added. This increases the distance between the nucleus and outermost electrons. • Atomic radius decreases in moving from left to right along a period. This is due to increase in NUCLEAR charge which TENDS to pull the electrons closer to the nucleus and reduces the size of the atom.