What is an Ion?

Ions

1. Ions are charged particles present in compounds of metals and non-metals.
2. Types of ions:
1. Monoatomic ion → formed from a single atom (e.g., Na⁺, Cl⁻)
2. Polyatomic ion → ion made of a group of atoms with a net charge (e.g., SO₄²⁻, OH⁻).

Types of Ions

1. Cation – Positive Ion: Formed when an atom loses electrons.
   1. Example: Na⁺ (Sodium ion)
2. Anion – Negative Ion
   1. Formed when an atom gains electrons.
   2. Example: Cl⁻ (Chloride ion)

Example: Sodium Chloride (NaCl)

1. Constituents:
1. Sodium ion (Na⁺) → Cation
2. Chloride ion (Cl⁻) → Anion
2. Together they form an ionic compound.

Polyatomic Ion

1. a cluster of atoms joined by bonds that together possess an overall charge.
2. Examples:
1. Hydroxide ion (OH⁻)
2. Sulfate ion (SO₄²⁻)

Non-metals vs Metals: Molecules or Lattice?

Non-metals

1. Non-metals combine through covalent bonds.
2. This results in discrete molecules (small independent particles).
3. Examples: O₂, H₂O, CO₂, N₂
   That’s why we say: “molecules of non-metals”

Metals

1. Metals combine through metallic bonds.
2. Atoms release their valence electrons → electrons form a “sea of electrons”.
3. Metals do not exist as discrete molecules; instead, they form a metallic crystal lattice (solid structure).
4. Examples: Na, Fe, Cu (all exist as crystal lattices).
   ???? That’s why we say: “metallic lattice” or “metallic crystal”, not molecules.

✅ Final Comparison

Property	Non-metals	Metals
Bond type	Covalent bond	Metallic bond
Basic unit	Molecule	Metallic lattice
Examples	O₂, H₂O, CO₂	Na, Fe, Cu
Nature	Discrete small particles	Continuous solid lattice

Final Answer:

1. Non-metal → molecules
2. Metal → metallic lattice (not molecules)

 

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