Bonding and Structure

A vocabulary-style set of flashcards covering the key concepts of bonding and structure from the notes.

Ion

An atom or molecule that carries a net electric charge due to gain or loss of electrons (e.g., Cu → Cu2+ + 2e−).

Cation

A positive ion formed when an atom loses electrons; attracted toward the cathode in electrolysis.

Anion

A negative ion formed when an atom gains electrons; attracted toward the anode in electrolysis.

Ionic bond

An omnidirectional electrostatic attraction between oppositely charged ions that holds them in a lattice.

Ionic lattice

A repeating, rigid arrangement of ions in a solid ionic compound (giant ionic lattice).

Octet rule

Ions tend to have a full outer shell of eight electrons and are often isoelectronic with noble gases.

Isoelectronic

Having the same electronic configuration as a noble gas (e.g., Ca2+ is isoelectronic with Ar).

Dot-and-cross diagram

A diagram showing electrons from different atoms with dots and crosses to represent transfer or sharing of electrons.

Dative covalent bond

A covalent bond where both shared electrons come from one atom (coordinate bond); e.g., Al2Cl6.

Covalent bond

A strong bond formed by the sharing of a pair of electrons between two atoms.

Pure (non-polar) covalent bond

A covalent bond in which electrons are shared equally due to similar electronegativities.

Polar covalent bond

A covalent bond in which electrons are shared unequally, producing partial charges on atoms.

Polarization

Distortion of an ion’s electron cloud by another ion, giving covalent character to a bond.

Polarizing power

The ability of a cation to distort an anion’s electron cloud; higher with small, highly charged cations.

Polarizable

Able to have its electron cloud distorted by an external charge.

Electronegativity

The ability of an atom in a covalent bond to attract the shared electrons toward itself.

Pauling scale

A scale used to quantify electronegativity values for elements.

Electronegativity trend across a period

Increases from left to right due to increasing nuclear charge and constant shielding.

Electronegativity trend down a group

Decreases down a group as atomic size increases and shielding grows.

Bond polarity

A bond in which electron distribution is asymmetrical due to electronegativity differences.

Dipole moment

μ = product of the charge difference and the distance between centers of positive and negative charges; measures polarity.

Polar molecule

A molecule with a net dipole moment because polar bonds do not cancel (e.g., H2O).

Bond length

The distance between the nuclei of two bonded atoms.

Bond energy

The energy required to break one mole of covalent bonds in the gaseous state.

VSEPR theory

Valence shell electron pair repulsion; electron pairs repel to minimize repulsion, determining molecular shapes.

Lone pair

A non-bonding pair of electrons that affects molecular geometry.

Linear (molecule)

Molecular geometry with 2 bond pairs and 0 lone pairs; bond angle ~180° (e.g., BeF2).

Trigonal planar

Molecular geometry with 3 bond pairs and 0 lone pairs; bond angle ~120° (e.g., BF3).

Tetrahedral

Molecular geometry with 4 bond pairs and 0 lone pairs; bond angle ~109.5° (e.g., CH4).

Trigonal pyramidal

3 bond pairs and 1 lone pair; bond angle ~107° (e.g., NH3).

Bent

2 bond pairs and 1–2 lone pairs; bond angle less than ~109.5° (e.g., H2O ~104.5°).

Trigonal bipyramidal

Five bond pairs (and zero lone pairs); bond angles around 90° and 120°.

Octahedral

Six bond pairs (zero lone pairs); bond angles ~90°.

Diamond

Giant covalent structure where each carbon bonds to four others; very hard with a high melting point; non-conductor.

Graphite

Layered giant covalent structure where each carbon bonds to three others in sheets; conducts electricity due to delocalised electrons.

Allotrope

Different physical forms of the same element in the same state (e.g., diamond and graphite).

Graphene

A single layer of graphite; a 2D nanomaterial that conducts electricity and is very strong.

Delocalised electron

An electron not associated with a single atom, free to move in a lattice (e.g., in graphite and metals).

Metallic bonding

Giant lattice of metal cations in a sea of delocalised electrons; non-directional, strong attraction.

Sea of delocalised electrons

The mobile electrons in a metal lattice that enable electrical and thermal conductivity.

Malleability

The ability of a material to be hammered into shape without breaking.

Ductility

The ability of a material to be drawn into wires.

Electrical conductivity (metals)

Conductivity due to the movement of delocalised electrons under an electric field.