Trends in Atomic Radius

The number of electron shells surrounding the nucleus increases from left to right across a period.

The number of electron shells increases as you move down a group.

The inner electrons shield the outer electrons from the full attraction of the nucleus, making the outer electrons less tightly held, leading to a larger atomic radius.

As the number of protons increases, the attraction between the nucleus and the electrons increases, pulling them closer and decreasing the atomic radius.

The decrease in atomic radius across a period is mainly due to the increase in nuclear charge, which outweighs the shielding effect.

The increase in atomic radius down a group is due to the increase in the number of electron shells, which overcomes the increase in nuclear charge.

Across a period, the number of electron shells stays the same.

Down a group, the number of electron shells increases.

The shielding effect decreases across a period because the number of inner electrons stays the same, while the nuclear charge increases.

The shielding effect increases down a group because the number of inner electrons increases, creating a stronger shield against the nucleus.

As you move down a group, the nuclear charge also increases, but the shielding effect increases even more.

The strong attraction between the nucleus and the electrons in a smaller atom leads to a higher ionization energy. It takes more energy to remove an electron from a smaller atom.

The larger atomic radius of elements down a group means that the outermost electrons are farther from the nucleus, and are easier to remove.

The smaller atomic radius of elements across a period means that the outer electrons are more attracted to the nucleus, making it harder to remove them.

Atoms with a larger atomic radius tend to have a lower electronegativity. The farther away the valence electrons are from the nucleus, the less they attract electrons from other atoms.

Atoms with a smaller atomic radius tend to have a higher electronegativity. The closer the valence electrons are to the nucleus, the more they attract electrons from other atoms.