Periodic Trends
Across a period the effective nuclear charge climbs, so ionization energy, electronegativity, and electron affinity all trend upward; down a group the added shells win and each of these falls.
Pick which element is higher, or rank them, for the property named in each problem below.
Common Questions
What is ionization energy and how does it trend?
Ionization energy is the energy needed to remove an electron from an atom. It increases across a period (more protons hold electrons tighter) and decreases down a group (outer electrons are farther from the nucleus and easier to remove).
What is electronegativity and how does it trend?
Electronegativity is an atom's ability to attract shared electrons in a bond. It increases across a period and decreases down a group. Fluorine is the most electronegative element.
What is electron affinity?
Electron affinity is the energy change when an atom gains an electron. A more negative electron affinity means the atom more readily accepts an electron. It generally increases across a period and decreases down a group (with exceptions).
Why do periodic trends exist?
Trends arise from two competing factors: increasing nuclear charge (more protons pull electrons closer) across a period, and increasing electron shells (electrons are farther away) down a group. The balance of these factors determines each property.