Chart of Periodic Table Trends

Electronegativity

Electronegativity reflects how easily an atom can form a chemical bond. Generally, electronegativity increases from left to right and decreases as you move down a group. Keep in mind, the noble gasses (column at the right-hand side of the periodic table) are relatively inert, so their electronegativity approaches zero (exception to the overall trend). The larger the difference between electronegativity values, the more likely two atoms are to form a chemical bond.

Ionization Energy

Ionization energy is the smallest amount of energy needed to pull an electron away from an atom in the gas state. Ionization energy increases as you move across a period (left to right) because the increasing number of protons attracts the electrons more strongly, making it harder to remove one.

As you go down a group (top to bottom), ionization energy decreases because an electron shell is added, moving the outermost electron further away from the atomic nucleus.

Atomic Radius (Ionic Radius)

Atomic radius is the distance from the nucleus to the outermost stable electron while ionic radius is half the distance between two atomic nuclei that are just touching each other. These related values display the same trend in the periodic table.

As you move down the periodic table, elements have more protons and gain an electron energy shell, so atoms become larger. As you move across a row of the periodic table, there are more protons and electrons, but the electrons are held more closely to the nucleus, so the overall size of the atom decreases.

Metallic Character

Most of the elements in the periodic table are metals, which means they display metallic character. Properties of metals include metallic luster, high electrical and thermal conductivity, ductility, malleability, and several other traits. The right-hand side of the periodic table contains the nonmetals, which do not display these properties. As with the other properties, metallic character relates to the configuration of valence electrons.

Electron Affinity

Electron affinity is how easily an atom accepts an electron. Electron affinity decreases moving down a column and increases moving left to right across a row of the periodic table. The value cited for an atom's electron affinity is the energy gained when an electron is added or the energy lost when an electron is removed from a single-charged anion. This depends on the configuration of the outer electron shell, so elements within a group have a similar affinity (positive or negative). As you might expect, elements that form anions are less likely to attract electrons than those that form cations. Noble gas elements have an electron affinity near zero.