Atom size is determined by the number of shells and how many protons and electrons are present in the atom. Any atom in a higher number period (row) is larger than any atom in a lower number period, since the number of electron shells increases as the number of the period increases. Within the same period, atoms get smaller as you move towards the right. This is because the atomic number increases, increasing the number of protons in the nucleus. These protons attract the surrounding electrons, pulling them in closer, and shrinking the total size of the atom.

In general, atomic radius will increase as you move down and to the left. This makes helium the smallest atom and francium the largest.

Ions of atoms vary in their size. When an atom gains electrons the atomic size increases, and when an atom loses electrons the atomic size decreases. Nitrogen with a formal charge of negative three will have the largest size because it has the most electrons. Remember that adding electrons will cause a negative ion, while removing electrons will cause a positive ion.

Moving left to right on the periodic table causes an increase in atomic number (number of protons) as well as electron affinity and electronegativity.

Atomic radius, however, will decrease when moving left to right. As more protons are added to the nucleus, they have a stronger attraction to the electrons. This pulls the electrons closer to the nucleus, resulting in a smaller atomic radius.

The periodic table is set up so that we can quickly tell which elements will react in a similar chemical fashion. The elements from the same group, that is the same column, will have similar properties. This is due to the same number of valence electrons in the outer shell.

Ionization energy is the amount of energy needed to remove an electron from an atom. Alkali metals only need to lose one electron in order to achieve the stable noble gas octet. As a result, the loss of this electron requires very little energy since the resulting ion is favorably stable. This property causes alkali metals (found in group I) to have the lowest first ionization energies.

The trend for atomic radius is as follows: atomic radius increases from right to left within a row and from top to bottom within a group on the periodic table.

Fluorine is the most electronegative element. The trend for electronegativity is as follows: electronegativity increases from left to right within a row and from bottom to top within a group of the periodic table.

Francium is the least electronegative element. The trend for electronegativity is as follows: electronegativity increases from left to right within a row and from bottom to top within a group of the periodic table.

The trend for atomic radius is as follows: atomic radius increases from right to left within a row and from top to bottom within a group on the periodic table.

Lithium has the greatest ionization energy because it is the smallest of the options available. The smaller an element/atom is, the closer to the nucleus of the atom the valence electrons are. The closer valence electrons are to the center of an atom, the harder it us to take one away, because it's strongly attracted to the protons in the center of an atom. The trend for ionization energy is as follows: ionization energy increases from left to right within a row and from bottom to top within a group on the periodic table