Understanding atomic properties and their periodic trends
The distance from the nucleus to the outermost electron shell.
Trend: Increases down a group, decreases across a period.
Reason: Down a group: more electron shells. Across a period: increased nuclear charge pulls electrons closer.
Energy required to remove an electron from an atom.
Trend: Decreases down a group, increases across a period.
Reason: Down a group: outer electrons are farther from nucleus. Across a period: increased nuclear charge holds electrons tighter.
Energy change when an atom gains an electron.
Trend: Generally decreases down a group, increases across a period.
Reason: Down a group: added electron is farther from nucleus. Across a period: increased nuclear charge attracts electrons more strongly.
Ability of an atom to attract electrons in a bond.
Trend: Decreases down a group, increases across a period.
Reason: Down a group: increased distance and shielding reduce attraction. Across a period: increased nuclear charge enhances electron attraction.
Reduction of nuclear charge felt by outer electrons due to inner electrons.
Trend: Increases down a group, remains relatively constant across a period.
Reason: Down a group: more electron shells increase shielding. Across a period: electrons are added to same shell with similar shielding.
Net positive charge experienced by valence electrons.
Trend: Increases across a period, changes slightly down a group.
Reason: Across a period: nuclear charge increases while shielding remains similar. Down a group: increased nuclear charge is offset by increased shielding.