Difference Between Atoms and Molecules

Definitions

• Atom: A single particle composed of one type of element.
• Molecule: A particle that contains two or more atoms. These atoms can be of the same or different types.

Examples

• Helium (He): Composed of single atoms, a pure element.
• Hydrogen Gas (H₂): A molecule since it consists of two hydrogen atoms bonded together, also a pure element.
• Water (H₂O): A molecule composed of two hydrogen atoms and one oxygen atom, not a pure element due to mixing of different types of atoms.

Pure Elements vs Compounds

• Pure Element: Composed entirely of one type of atom (e.g., O₂, Ne).
• Compound: Composed of different types of atoms (e.g., CO₂).

Examples

• Oxygen (O₂): A molecule and a pure element.
• Carbon Dioxide (CO₂): A molecule and a compound.
• Neon (Ne): Composed of single atoms, a pure element.
• Fluorine (F₂): A molecule and a pure element.

Difference Between Atoms and Ions

Definitions

• Atom: Electrically neutral with equal number of protons and electrons.
• Ion: Contains unequal numbers of protons and electrons, resulting in a charge.

Types of Ions

• Cation: Positively charged ion (more protons than electrons).
• Anion: Negatively charged ion (more electrons than protons).

Examples

• Aluminum Atom vs Aluminum Ion:
  • Aluminum Atom: 13 protons, 13 electrons (neutral).
  • Aluminum Ion (3+ charge): 13 protons, 10 electrons (cation).
• Phosphorus Ion (P³⁻): Anion with 15 protons and 18 electrons.

Compounds

Types of Compounds

1. Ionic Compounds: Composed of metals and nonmetals, involving transfer of electrons.
2. Covalent (Molecular) Compounds: Composed of nonmetals, involving sharing of electrons.

Examples

• Sodium Chloride (NaCl): Ionic compound (metal + nonmetal).
• Water (H₂O): Covalent compound (nonmetals).
• Carbon Monoxide (CO): Covalent compound (nonmetals).
• Magnesium Chloride (MgCl₂): Ionic compound (metal + nonmetal).
• Sulfur Hexafluoride (SF₆): Covalent compound (nonmetals).
• Calcium Oxide (CaO): Ionic compound (metal + nonmetal).

Exception

• Ammonium Chloride (NH₄Cl): Although composed of nonmetals, it is an ionic compound due to the presence of ions (NH₄⁺ and Cl⁻).

General Rule

• Ionic Compounds: Typically metal + nonmetal.
• Covalent Compounds: Typically two nonmetals.

Note

• Exceptions: Some compounds like NH₄Cl may not follow the typical rules due to ionic components.