atomic radii?

Question

why the pattern of atomic radii in the periodic table? (move down in a family, or group, it increases, move across a period and it decreases.) does it have to do with the structure of the atom and atomic mass?

Answer 1

As you move down a group, atomic radii increases because there are more shells. For example, potassium (K) has a larger atomic radius than sodium (Na) because it has one more shell (K has 4 shells and Na has 3 shells).

As you move across a period, the number of shells remains the same, but the atomic number goes up. When the atomic number goes up, it means that there are more protons. More protons means more protons (in the nucleus) pulling on the surrounding electrons, thus making the radii smaller.

Answer 2

okay...as you go down a group the radii increases correct?? this is because each element after another going down gains an "energy level" thus allowing for more electrons to be held. as you are moving across periods... you gain 1 valence electron (except for the transistion elements) and you also gain a proton. these two are attracted to eachother and they pull close to eachother decreasing the size of an atom.

Answer 3

When we move down the periodic table, a new shell keeps getting added to the outermost level... Thus obviously it increases the radius...

And as you go to the right, the number of electrons on the outermost shell keeps increasing. Thus the net negative charge on the outermost shell increases, which increases the attraction to it and the positively charged nucleus, thus the pull being stronger results in the radius becoming lesser...

Answer 4

Hi. The atomic radius is a function of electron 'clouds'. More electrons come with more protons, and more protons usually means more neutrons.

Answer 5

across = decrease b/c of greater nuclear pull (of the protons on the electrons). down = increase b/c of shielding (more electrons)