What causes the trend in atomic radius?

Answer 1

As you go across a period, radius shrinks because you are adding protons. The added positive charge increases pull on the electron shells.

As you go down a group, radius gets larger because you are increasing shells of electrons. This increases shielding of the nucleus' positive charge, so the electrons are not pulled in as much.

Answer 2

The nuclear charge and the amount of filled shells the atom has. A larger nuclear charge will bring electrons closer to the nucleus. More shells between the valence shell and the nucleus will limit the pull of the nucleus on valence shells, making them spread out and creating a larger radius.

Answer 3

The "atomic radius" is usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius.

The radius can change due to the phase of the matter (solid liquid, gas, plasma) and if there are other forces applied.

Answer 4

The trend for atomic radius, and most other trends on the Periodic Table, can be explained by the amount of attraction between the positively charged nucleus and the negatively charged electrons. Other factors that come into play are the number of electrons in the outer energy level (valence shell) and the distance between the outer electrons and the nucleus (number of energy levels.)

Answer 5

1) Nuclear Charge

2) Screening Effect or or shielding effect

Answer 6

The nuclear charge, number of electron shells, and shielding

Answer 7

effective nuclear charge and screening effect