Chemistry: bonding and properties of substances (grade 10) · lesson

Ionic, covalent, and metallic bonds

💡 Metal plus nonmetal usually forms ionic bonds, two nonmetals share electrons, and metals share a sea of electrons.

In an ionic bond, a metal gives electrons to a nonmetal. Sodium gives one to chlorine, making Na⁺ and Cl⁻ ions that attract.

In a covalent bond, two nonmetals share electrons. Water's hydrogen and oxygen atoms are held by covalent bonds.

In a metal, atoms share electrons that are free to move through the whole piece.

🧠 Let's work it out

Classify each atom as metal or nonmetal.
One of each: ionic.
Both nonmetals: covalent.
All metals: metallic.

What do you think comes next?

ionic bond: attraction between ions formed by electron transfer
covalent bond: a shared pair of electrons

🔗 Khan Academy: Chemical bonding · Khan Academy (free) ↗

💡 Each shared pair of electrons is one covalent bond.

A single bond is one shared pair, or two electrons. A double bond is two shared pairs (four electrons). A triple bond is three shared pairs (six electrons).

Nitrogen atoms in N₂ share three pairs, so N₂ has a triple bond.

🧠 How to think about it

Count the shared pairs, not the single electrons. Two electrons = one pair = one bond.

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Properties reveal the bond type

💡 Melting point and when a substance conducts tell you what kind of particles it has.

Ionic compounds have high melting points because many strong attractions must break. They conduct only when melted or dissolved, when ions can move.

Metals conduct even as solids, because their electrons are free to move.

Molecular substances often have low melting points and do not conduct, because they have no free charges.

🧠 Let's work it out

Use two clues.
Conducts as a solid → metal.
Conducts only when dissolved, high melting point → ionic.
Never conducts, low melting point → molecular.

What do you think comes next?

conduct: to let electric current flow

Attractions between molecules

💡 Stronger attractions between particles mean a higher boiling point, and polar and nonpolar substances don't mix.

Boiling pulls whole molecules apart from each other. It does not break the bonds inside each molecule.

Water is polar: one end is slightly negative and the other slightly positive. Water molecules attract each other strongly, through hydrogen bonds. Methane is nonpolar, with weak attractions, so it boils far colder.

Polar water molecules stick to each other and push nonpolar oil aside. That is why oil and water separate.

🧠 How to think about it

Rank attractions: weak between nonpolar molecules, stronger hydrogen bonds between water molecules, strongest between ions in salt. Boiling points follow the same order.

polar: having a slightly positive end and a slightly negative end

🔗 PhET: Molecule Polarity · PhET Interactive Simulations (free) ↗

Ionic, covalent, and metallic bonds

Single, double, and triple bonds

Properties reveal the bond type

Attractions between molecules