Chemistry Unit 5

Nuclear Charge

  • The positive charge of the nucleus, determined by the number of protons.

  • Higher nuclear charge results in a stronger attraction for electrons, leading to changes in atomic properties.

Shielding

  • The effect of inner electrons reducing the full nuclear charge experienced by outer electrons.

  • More inner electrons result in greater shielding, reducing the effective nuclear charge ZeffZ_{eff}.

Atomic Radius

  • Definition: The distance from the nucleus to the outermost electron.

  • Trends:

    • Decreases across a period (left to right) due to increasing nuclear charge.

    • Increases down a group (top to bottom) due to adding electron shells and increased shielding.

Ionization Energy

  • Definition: The energy required to remove an electron from a gaseous atom or ion.

  • Trends:

    • Increases across a period due to increasing nuclear charge and decreasing atomic size.

    • Decreases down a group due to increasing atomic size and shielding.

Electronegativity

  • Definition: The ability of an atom to attract electrons in a chemical bond.

  • Trends:

    • Increases across a period due to increasing nuclear charge.

    • Decreases down a group due to increasing atomic size and shielding.

Reactivity

  • Metals: Reactivity increases down a group (more easily lose electrons) and decreases across a period (harder to lose electrons).

  • Nonmetals: Reactivity decreases down a group (harder to gain electrons) and increases across a period (easier to gain electrons).

AIMES Chart

  • Atomic Radius, Ionization Energy, Metallic Character, Electronegativity, Shielding.

  • A visual aid to understand and remember periodic trends.

Valence Electrons

  • Electrons in the outermost shell of an atom that participate in chemical bonding.

  • Determine the chemical properties of an element.

Ions

  • Atoms that have gained or lost electrons, resulting in a net charge.

  • Cations: Positively charged ions (lose electrons).

  • Anions: Negatively charged ions (gain electrons).

Lewis Dot Diagrams

  • Diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.

  • Useful for visualizing valence electrons and predicting bonding patterns.