The Element with the Smallest Atomic Radius: Helium (Number 9 in Periodic Table)

In the periodic table, one important property that helps us understand the behavior and characteristics of elements is their atomic radius. The atomic radius is defined as half the distance between the nuclei of two identical bonded atoms. It measures the distance from an atom's nucleus to its outermost electron orbital.

As we move across a period in the periodic table, we notice that the atomic radius decreases. This is because the nuclear charge increases, attracting electrons more closely to the nucleus. In contrast, as we progress down a group, the number of electrons and shells increases, causing the atomic radius to increase.

The element with the smallest atomic radius is helium (Number 9 in the periodic table), which has an atomic radius of just 31 picometers. This means that the electrons in helium are pulled extremely closely to its nucleus, resulting in a very small atomic radius.

Helium's unique properties can be attributed to its position in the top period and farthest right group of the periodic table. Its small atomic radius is due to the strong attraction between the positively charged protons in its nucleus and the negatively charged electrons.

In summary, understanding the atomic radius of elements like helium (Number 9) is crucial in grasping many properties and behaviors of atoms. By recognizing trends in the periodic table, such as changes in atomic radius across periods and groups, we can gain insight into the fundamental nature of matter.

Number 9 in periodic table