Module 2: Chemical Bonding: Properties of Compounds

What is a chemical bond?

The force that holds atoms together in compounds.

Why do atoms form bonds?

To achieve stability by completing their outermost electron shell (octet rule).

What is the octet rule?

Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their valence shell.

What is an ionic bond?

The transfer of electrons from a metal to a nonmetal, producing cations and anions.

What is a covalent bond?

The sharing of electrons between two nonmetal atoms.

What is a metallic bond?

The attraction between metal cations and a "sea of delocalized electrons."

State 3 properties of ionic compounds.

High melting/boiling points, soluble in water, conduct electricity when molten or dissolved.

Why are ionic compounds brittle?

Shifting layers of ions cause repulsion between like charges, breaking the crystal structure.

State 3 properties of covalent compounds.

Low melting/boiling points, usually insoluble in water, poor conductors of electricity.

Why do covalent compounds have low melting and boiling points?

They have weak intermolecular forces that are easy to break.

What gives metals their malleability and ductility?

The delocalized electrons allow layers of atoms to slide over each other.

Why are metals good conductors of heat and electricity?

The mobile sea of electrons carries charges and energy easily.

What is electronegativity?

The ability of an atom to attract shared electrons in a bond.

What type of bond forms if ΔEN > 1.7?

Ionic bond.

What type of bond forms if ΔEN is 0.4 - 1.7?

Polar covalent bond.

What type of bond forms if ΔEN < 0.4?

Nonpolar covalent bond.

Example of an ionic compound.

NaCl (table salt).

Example of a covalent compound.

H₂O (water).

Example of a metallic bond.

Copper (Cu) in electrical wires.

What does VSEPR stand for?

Valence Shell Electron Pair Repulsion theory.

What does VSEPR theory state?

Electron pairs around a central atom arrange themselves to minimize repulsion.

Shape of a molecule with 2 bonding pairs, no lone pairs.

Linear (180°).

Shape of a molecule with 3 bonding pairs, no lone pairs.

Trigonal planar (120°).

Shape of a molecule with 4 bonding pairs, no lone pairs.

Tetrahedral (109.5°).

Shape of H₂O (2 bonding pairs, 2 lone pairs).

Bent/angular.

Shape of NH₃ (3 bonding pairs, 1 lone pair).

Trigonal pyramidal.