Periodic Trends

The periodic table of elements is a highly organized chart that puts elements in groups with other elements of similar behavior. When organized by atomic number, elements display several trends. Atomic radius increases down the groups from top to bottom and decreases across the periods from left to right. Ionization energy is strongly influenced by atomic radius. The further the electrons are away from the nucleus, the less pull the nucleus will exert on them. This means that it takes less energy to remove an electron from these elements.

Electronegativity is also influenced by radius. Elements with a smaller radius tend to pull electrons toward themselves more than larger atoms. Elements that tend to lose electrons are on the left of the table (metals) and elements that tend to gain electrons are toward the right (non-metals). The larger atoms tend to lose electrons as a result of the increased distance between the electrons and the nucleus. The inner electrons also shield the outer electrons from the nucleus. These two factors result in a weaker pull by the nucleus on the valence electrons. By analyzing all of the trends in the periodic table, you have now unlocked all of the “secrets” this chart holds.