periodic table

Across a period, nuclear charge increases as the number of protons increases. Increase in shielding effect is negligible as successive electrons are added to the same outermost shell. Since the increase in nuclear charge outweighs the increase in shielding effect, valence electrons are more strongly attracted to the nucleus.

Atomic radius increases across the period

Down a group, nuclear charge increases as the number of protons increases. As the number of inner shells increases, valence electrons are further away from the nucleus. Valence electrons are less strongly attracted to the nucleus

Atomic radius increases down the group

Nuclear charge remains constant (as nuclear charge of both atom and its cation are the same). The cation has one less shell of electrons that it’s atom. Hence, it’s valence electrons experience lower shielding effect and are more strongly attracted to the nucleus

Cationic radius is smaller than corresponding parent atom

Nuclear charge remains constant (as nuclear charge of both atom and its anion are the same) The anion has more electrons than its atom. Hence, the attraction between the nucleus and its valence electrons decreases

anionic radius is greater than corresponding parent atom

Nuclear charge increases as the number of protons increases. Shielding effect is the same as the ions are isoelectronic. Valence electrons are more strongly attracted to the nucleus

Ionic radius of isoelectronic ions decreases across the period

Across a period, nuclear charge increases as number of protons increase. Increase in shielding is negligible as successive electrons are added to the same valence shells. Since the increase in nuclear charge outweighs the increase in shielding effect, valence electrons are more strongly attracted to the nucleus. More energy is required to remove a valence electron from each atom

First ionisation energy generally increases across the period

Down a group, nuclear charge increases as number of protons increases. As number of inner shells increase, valence electrons are further away from the nucleus and shielding effect increases. Valence electrons are less strongly attracted to the nucleus. Less energy is required to remove the valence electron

First ionisation energy decreases down a group

Electronegativity

Ability of an atom in a molecule to attract bonding electrons to itself

Across a period, nuclear charge increases as number of protons increases. Increase in shielding is negligible as successive electrons are added to the same outermost shell. Since the increase in nuclear charge outweighs the increase in shielding effect, the ability of the atom to attract bonding electrons to itself increases.

Electronegativity increases across a period

Down a group, nuclear charge increases as number of protons increases. As number of inner shells increase, valence electrons are further away from the nucleus and shielding effect increases. Hence, the ability of the atom tonatttact bonding electrons to itself decreases.

Electronegativity decreases down a group

Electrical conductivity increases from Na to Al, drops sharply from Al to Si, decreases to 0 from P to Cl