Periodic Trends - AP Chemistry

Covalent radius decreases across a period. Same trend as atomic radius due to nuclear charge.

Noble gases have positive or zero electron affinity. Stable electron configurations resist gaining electrons.

Density generally increases across a period. More protons and electrons in smaller volume.

Reactivity increases down the group. Larger size makes valence electrons easier to lose.

Metallic character decreases across a period. Atoms lose electrons less easily with higher nuclear charge.

Helium. Small size and high nuclear charge resist electron removal.

Ionic radius increases down a group. Additional electron shells increase ionic size.

Cesium. Largest number of electron shells among all elements.

Ionic radius decreases across a period. Higher nuclear charge contracts electron clouds around ions.

P-block. Contains fluorine and other highly electronegative nonmetals.

Noble gases. Electronegativity undefined for unreactive noble gases.

Boiling points vary; metals generally increase. Stronger metallic bonding with more valence electrons.

Melting points vary but generally increase across metals. More bonding electrons and smaller size strengthen bonds.

Melting points decrease down the group. Weaker metallic bonding with larger atomic size.

Helium. Highest nuclear charge with no shielding electrons.

High ionization energy due to full valence shell. Stable electron configurations require maximum energy to ionize.

Varies slightly but generally high. D-electrons provide consistent metallic bonding across period.

Francium. Largest atomic size with lowest nuclear charge effect.

Electron affinity becomes less negative down a group. Increased size and shielding reduce attraction for electrons.

Electronegativity increases across a period. Higher nuclear charge increases attraction for electrons.

Covalent radius decreases across a period. Same trend as atomic radius due to nuclear charge.

Density generally increases across a period. More protons and electrons in smaller volume.

Noble gases have positive or zero electron affinity. Stable electron configurations resist gaining electrons.

Reduction in effective nuclear charge by inner electrons. Core electrons block valence electrons from nuclear attraction.

Varies widely, often multiple oxidation states. D-electrons can be lost in different combinations.

Density generally increases down a group. More massive atoms with larger size pack more densely.

Noble gases have a full valence shell. Complete octets provide maximum stability and low reactivity.

Boiling points vary; metals generally increase. Stronger metallic bonding with more valence electrons.

Noble gases. Electronegativity undefined for unreactive noble gases.