Chem Unit 3 test

Aufbau Principle

Electrons fill the lowest-energy orbitals available first.

Pauli Exclusion Principle

An orbital can hold a maximum of two electrons with opposite spins.

Orbital

An area around the nucleus where an electron is likely to be found.

Electron Configuration

A notation that shows how electrons are distributed among energy levels and subshells.

Orbital Filling Order

The order in which electrons fill orbitals from lowest to highest energy.

Main-Group Elements

Elements in Groups 1, 2, and 13–18 of the periodic table.

Alkali Metals

Group 1 elements with one valence electron that typically form +1 ions.

Alkaline Earth Metals

Group 2 elements with two valence electrons that typically form +2 ions.

Boron Family

Group 13 elements with three valence electrons.

Carbon Family

Group 14 elements with four valence electrons.

Halogens

Group 17 elements with seven valence electrons that typically form −1 ions.

Noble Gases

Group 18 elements with full valence shells that are generally unreactive.

Valence Electrons

Electrons in the outermost occupied main energy level that influence bonding and reactivity.

Valence Electron Configuration

The part of an electron configuration that describes the valence-shell electrons.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Ion Formation

The process in which an atom gains or loses electrons to become a charged particle.

Typical Main-Group Ion Charges

Group 1: +1; Group 2: +2; Group 13: commonly +3; Group 15: commonly −3; Group 16: −2; Group 17: −1; Group 18: typically 0.

Cation Electron Configuration

The electron configuration of an atom after it loses electrons.

Anion Electron Configuration

The electron configuration of an atom after it gains electrons.

Atomic Radius

A measure of atomic size.

Periodic Trend

A predictable pattern in an element property across periods or down groups of the periodic table.

Atomic Radius Trend Down a Group

Atomic radius generally increases down a group because additional occupied energy levels and shielding place outer electrons farther from the nucleus.

Atomic Radius Trend Across a Period

Atomic radius generally decreases from left to right because increasing nuclear charge pulls electrons closer within the same main energy level.

First Ionization Energy

The energy required to remove the first electron from a neutral gaseous atom.

First Ionization Energy Trend Down a Group

First ionization energy generally decreases down a group because outer electrons are farther from the nucleus and more shielded.

First Ionization Energy Trend Across a Period

First ionization energy generally increases from left to right because nuclear attraction generally increases.

Electronegativity

An atom's ability to attract shared electrons in a chemical bond.

Electronegativity Trend Down a Group

Electronegativity generally decreases down a group because bonding electrons are farther from the nucleus and more shielded.

Electronegativity Trend Across a Period

Electronegativity generally increases from left to right as nuclear attraction for shared electrons increases.

Nuclear Attraction

The electrostatic attraction between the positively charged nucleus and negatively charged electrons.

Cation Size Compared with a Neutral Atom

A cation is generally smaller than its neutral atom because it loses electrons, reducing electron repulsion and sometimes losing an occupied energy level.

Anion Size Compared with a Neutral Atom

An anion is generally larger than its neutral atom because added electrons increase electron–electron repulsion.

Isoelectronic Ion Size Trend

Among isoelectronic species, the species with more protons is generally smaller because its nucleus attracts the same number of electrons more strongly.