Curriculum
Science — First Preparatory
Unit 1: Matter
0/8
Unit 2: Forces
0/6
Unit 3: Life
0/6
Unit 4: Earth and Space
0/4
Text lesson
Chemical Bonds
Chemical Bonds
Ionic bonds and covalent bonds
Ionic bonds and covalent bonds
- An ionic bond forms between a metal and a non-metal.
- Electrons move from the metal to the non-metal, producing positive and negative ions that attract each other strongly.
- Example: sodium chloride NaCl.
- A sodium atom, arrangement 2, 8, 1, loses one electron and becomes Na+.
- A chlorine atom, arrangement 2, 8, 7, gains one electron and becomes Cl− (2, 8, 8).
- A covalent bond forms between two non-metals.
- The atoms share one or more pairs of electrons, so each outer level becomes full, and no electrons are permanently transferred.
| Substance | Type of bond | Number of shared electron pairs |
|---|---|---|
| Hydrogen H₂ | Covalent | One pair (single bond) |
| Oxygen O₂ | Covalent | Two pairs (double bond) |
| Nitrogen N₂ | Covalent | Three pairs (triple bond) |
| Water H₂O | Covalent | Two single bonds |
| Carbon dioxide CO₂ | Covalent | Two double bonds |
- Ionic compounds usually have high melting points, and they conduct electricity when melted or dissolved in water.
- Covalent compounds usually do not conduct electricity.
Chemical Bonds · 2 / 6