Chemical Bonding and Atomic Structure Fundamentals

The Octet Rule

In chemical compounds, atoms tend to exchange electrons with other atoms to complete 8 electrons in their valence shell, with the exception of hydrogen, which requires 2 electrons.

Ionic Bonds

Ionic bonds result from the electrical attraction between positive and negative ions. Metals typically form ionic compounds when reacting with nonmetals.

Properties of Ionic Bonds

• Solid at room temperature with very high melting and boiling points.
• Hard and resistant to scratching.
• Do not conduct electricity in a solid state.
• Soluble in water and conduct electricity when fused.

Covalent Bonds

Covalent bonds occur when two atoms share pairs of electrons to complete their valence shells.

Properties of Covalent Bonds

• Solid at room temperature.
• High melting and boiling points.
• Very hard.
• Do not conduct heat or electricity.
• Insoluble in water.

Metallic Bonds

Metallic bonds occur when positive metal ions share a cloud of electrons.

Properties of Metallic Bonds

• Solid at room temperature (except for mercury).
• High melting and boiling points.
• Excellent conductors of heat and electricity.
• Usually malleable and ductile.
• Hard, but prone to corrosion when exposed to air.

Fundamental Chemical Concepts

Atomic and Molecular Mass

• Atomic Mass: The mass of an atom measured in atomic mass units (u).
• Molecular Mass: The sum of the atomic masses of the atoms forming a molecule.

Atoms and Molecules

• Atom: The smallest portion of an element that can participate in a chemical compound.
• Molecule: A group of a specific number of atoms held together by covalent bonds.

Physical vs. Chemical Changes

• Physical Changes: Substances retain their nature and properties remain the same.
• Chemical Changes: The nature of the substance is modified, resulting in a new substance with different properties.

Chemical Reactions

• Effective Impact: Requires appropriate orientation and sufficient energy.
• Exothermic: Releases energy in the form of light, heat, or electricity.
• Endothermic: Absorbs energy in the form of light, heat, or electricity.

The Mole

A mole contains a mass in grams that coincides with its atomic or relative molecular mass and contains 6.023 × 10²³ particles (Avogadro's number).

Formula: 1 mol = 6.023 × 10²³ molecules = X grams