UNIT 4: Chemical Bonding and Structure

Ionic Bonds

Ionic Bonds

Bonds formed from the transfer of electrons from a metallic element to a non-metallic element, resulting in the formation of positively charged cations and negatively charged anions.

Cation

A positively charged ion formed when a metal loses electrons from its valence shell.

Anion

A negatively charged ion formed when a non-metal gains electrons.

Electrostatic Attractions

Strong attractions formed between oppositely charged ions (cations and anions) to form ionic compounds.

Ionic Lattice

An evenly distributed crystalline structure formed by ions arranged in a regular repeating pattern due to electrostatic forces of attraction between cations and anions.

Properties of Ionic Compounds

Different physical properties (melting/boiling points, electrical conductivity, and solubility) due to their different types of structure/bonding.

Covalent Bonds

Bonds formed between two non-metals through the sharing of electrons in molecular orbitals.

Lewis Structures

Simplified electron shell diagrams that show pairs of electrons around atoms, representing covalent bonds.

Resonance Structures

Different possible Lewis Structures for a molecule or ion that can be represented by resonance, indicating the delocalization of electrons.

Resonance Hybrid

The actual structure of a molecule or ion that is a combination of all the resonance structures, with electron density spread evenly between atoms.

Bond Polarity

The unequal sharing of electrons in a covalent bond due to differences in electronegativity, resulting in a polar bond.

Dipole Moment

A measure of how polar a bond is, with the direction of the dipole moment indicated by the arrow pointing towards the partially negatively charged end of the dipole.

Bond Energy

The energy required to break one mole of a particular covalent bond in the gaseous state, indicating the strength of the covalent bond.

Bond Length

The internuclear distance between two covalently bonded atoms, influenced by the forces of attraction between electrons and nuclei.

Multiple Bonds

Covalent bonds in which non-metals share more than one pair of electrons, resulting in different types of covalent bonds (single, double, and triple bonds).

VSEPR Theory

A theory that predicts molecular shape and bond angles based on the arrangement of electron pairs and lone pairs around the central atom.

Steric Number

The sum of the number of atoms and lone pairs around the central atom in a molecule.

Molecular Geometry

The three-dimensional arrangement of atoms in a molecule.

Giant Covalent Structures

Covalent lattices formed by nonmetal atoms that continue indefinitely, such as diamond, graphite, buckminsterfullerene, and graphene.

Dispersion Forces

Intermolecular forces that result from temporary dipoles created by the movement of electrons in atoms or molecules.

Dipole-dipole Attractions

Intermolecular forces between molecules with permanent dipoles.

Hydrogen Bonding

A special type of dipole-dipole attraction that occurs when a hydrogen atom is bonded to a highly electronegative atom (O, N, or F) and forms a bond with the lone pair of electrons on another molecule.

Allotrope

Different atomic or molecular arrangements of the same element in the same physical state.

Metallic Bonding

The bonding between metal atoms in a lattice structure, where the valence electrons are delocalized and free to move throughout the structure.

Alloys

Mixtures of two or more metals, or a metal and a nonmetal, that have improved properties compared to pure metals.

Alloys

Mixtures of metals or metals and non-metals that are physically combined but not chemically combined.

Metallic bonds

The binding of different metal ions in an alloy through their delocalized electrons, which are spread evenly throughout the lattice.

Distorted arrangement

The irregular arrangement of cations in an alloy due to the different sizes of the mixture of atoms, making it harder for the layers in the lattice structure to slide over each other.

Greater strength

Alloys are stronger than pure metals due to the distorted arrangement of cations in the lattice structure.

Resistance to corrosion/extreme temperatures

Alloys have higher resistance to corrosion and extreme temperatures compared to pure metals.

Brass

An alloy composed of copper and zinc, known for its strength and resistance to corrosion. Commonly used for door handles, hinges, and metal instruments.

Steel

An alloy composed of iron, carbon, and other elements such as chromium, vanadium, and molybdenum. It is very strong and commonly used in construction, bridges, and cars.

Solder

An alloy composed of lead and tin, known for its low melting point. It is used for joining metals in electrical circuits and in jewelry.

Bronze

An alloy composed of copper and tin, known for its hardness, strength, and resistance to corrosion. It is commonly used for medals, sculptures, and ship fittings.