As you move from left to right across a period, what happens to the atomic radii?

As you move from left to right across a period, atomic radii decreases.

Explanation:

Because the no. of protons increases in the nucleus of the atom as we move from left to right across a period on a periodic table. As the number of protons increases, the force of attraction between the protons and the electrons increases.

So, the last shell gets attracted closer, the atomic size also decreases.

Answer;

The atomic radii decreases

Explanation; The atomic size is determined by how far the last shell of electrons is away from the nucleus. Atomic radii decreases when we move from left to right across periodic table that is when we move left to right in a period because the number of valence electrons increases and the attraction between electron and the nucleous increases hence the shell shrinks towards the nucleous. The greater the number of protons, the more will be the force of attraction between between the protons and the electrons, i. e. the protons in the nucleus of the atom will pull the electrons closer with a greater force.