First ionization energy is the amount of energy required to remove an electron from an atom. Elements on the left side of the periodic table have less electrons in their outer shell. This means they will achieve the octet rule more easily by giving away their electrons, and are more likely to do so. Elements on the right side of the periodic table have more electrons in their outer shell, and will have an easier time achieving the octet rule by gaining electrons.

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.

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.

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.

The atomic radius of atoms will decrease across a period from left to right. Atomic radius is defined by two factors. The amount of electron shells in the atom, and the attraction between the protons in the nucleus and the electrons. Going across the period atoms will have more protons and electrons. This increases the amount of attraction between them and creates a higher nuclear charge. Since the attraction is stronger, the distance between the electrons and protons will be shorter. This means that that the atomic radius is smaller.

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.

For neutral atoms, the number of valence electrons is equal to the atom's main group number. According to the periodic table, oxygen is in group 6; therefore, it has 6 valence electrons in its outer shell.

Generally speaking, as you go across a period and up a group on the periodic table, electronegativity increases. Fluorine is the most electronegative element, with a Pauling scale electronegativity ranking of approximately 4.0.

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.

The amount of electrons in the outer shell is easily determined by which group an element is in. Elements in group 15 have 5 electrons in the outer shell. P is the only listed element in group 15.