How are ions formed?
Metals lose electrons to form positive ions (cations).
Non-metals gain electrons to form negative ions (anions).
What charges do metals in Groups 1, 2, and 3 form?
Group 1: +1 (e.g. Na⁺, K⁺)
Group 2: +2 (e.g. Mg²⁺, Ca²⁺)
Group 3: +3 (e.g. Al³⁺)
What charges do non-metals in Groups 5, 6, and 7 form?
Group 5: −3 (e.g. N³⁻)
Group 6: −2 (e.g. O²⁻, S²⁻)
Group 7: −1 (e.g. Cl⁻, Br⁻, I⁻)
What are the charges of common ions to learn?
Ag⁺, Cu²⁺, Fe²⁺, Fe³⁺, Pb²⁺, Zn²⁺
H⁺ (hydrogen)
OH⁻ (hydroxide)
NH₄⁺ (ammonium)
CO₃²⁻ (carbonate)
NO₃⁻ (nitrate)
SO₄²⁻ (sulfate)
How do you write the formula of an ionic compound?
Balance the total positive and negative charges so they cancel out.
Examples:
Na⁺ and Cl⁻ → NaCl
Mg²⁺ and Cl⁻ → MgCl₂
Al³⁺ and O²⁻ → Al₂O₃
What do dot-and-cross diagrams show?
Electron transfer between atoms to form ions — metals lose electrons, non-metals gain them.
Example:
Na donates one electron to Cl → Na⁺ and Cl⁻ form NaCl.
What is ionic bonding?
A strong electrostatic attraction between oppositely charged ions.
Why do ionic compounds have high melting and boiling points?
They have giant ionic lattices with strong electrostatic forces between ions that require lots of energy to break.
Why do ionic compounds not conduct electricity when solid?
Ions are fixed in place and cannot move.
Why do they conduct when molten or dissolved in water?
Ions are free to move and carry charge.
