2.4The Particulate Nature of Matter
Ions and ionic bonds — Combined Science 0653 - Chemistry Revision Notes & Topical Questions
5 min read 9 parts Lesson 12 of 13 1 quiz
Lesson summary
2.4 Ions and ionic bonds — COMBINED SCIENCE (CHEMISTRY) notes: Describe how ions form, how ionic bonds hold compounds together and the properties of ionic compounds.Ion — = electrically charged atom or group of atoms formed by the loss or gain of electrons.Reason — electrons are …
- Sodium chloride
- Overall charge
- Outer electrons
- Giant lattice
- Ion charge
- Electrostatic force
Part 1 of 7Formation of ions
Ion
- = electrically charged atom or group of atoms formed by the loss or gain of electrons.
Reason
- Reason electrons are lost or gained to give a full outer shell like a noble gas.
Cations
- Cations positive ions formed when atoms lose electrons; all metals form them.
Anions
- Anions negative ions formed when atoms gain electrons; non-metals form them.
Part 2 of 7Charges of simple ions
| Group | Ion charge | Example |
|---|---|---|
| I | 1+ | Na+ |
| II | 2+ | Mg2+ |
| VI | 2− | O2- |
| VII | 1− | Cl- |
Part 3 of 7Ionic bonding
Formation
- Formation metal atoms transfer their outer electrons to non-metal atoms.
Ionic bond
- = strong electrostatic force of attraction between oppositely charged ions.
Sodium chloride
- Sodium chloride sodium loses one electron to give Na+ and chlorine gains one electron to give Cl-;
- formula NaCl.
Overall charge
- Overall charge an ionic compound has no overall charge, so charges must balance.
- Magnesium oxideMg2+ and O2- give MgO.
- Magnesium chlorideMg2+ and two Cl- give MgCl2.
Part 4 of 7Dot-and-cross diagrams
Outer electrons
- Outer electrons only the outer shell electrons are shown, as dots and crosses.
Ions
- Ions each ion is drawn separately in square brackets with its charge at the top right.
Part 5 of 7Lattice structure
- Giant lattice
- ionic compounds have a regular, repeating arrangement of alternating positive and negative ions.
Part 6 of 7Properties of ionic compounds
| Property | Ionic compounds | Reason |
|---|---|---|
| State at room temperature | Usually solid | Strong forces between ions |
| Melting and boiling points | High | Much energy is needed to overcome the strong attractions in all directions |
| Conductivity when solid | Poor | Ions are fixed in the lattice |
| Conductivity when molten or dissolved | Good | Ions are free to move and carry charge |
- Ion charge
- the greater the charge on the ions, the stronger the forces and the higher the melting point.
- Magnesium oxide melts at a higher temperature than sodium chloride.
Part 7 of 7More from the specification
More from the specification
Dot-and-cross diagrams
- Structural diagrams showing how valence electrons are transferred between atoms to attain stable noble gas octets.
Giant ionic lattice structure
- A regular three-dimensional alternating network of positively and negatively charged ions held by strong electrostatic attractions.
Ion formation
- Metallic elements lose valence electrons to form positive cations, while non-metals like oxygen gain electrons to form negative anions.
Electrostatic attraction
- Omnidirectional forces of attraction binding oppositely charged ions tightly within crystal lattices.
Element
- A substance made of only one type of atom.
Oxygen
- A gas that relights a glowing splint.
Key terms
| Term | Meaning |
|---|---|
| Ion | Charged atom or group of atoms. |
| Cation | Positive ion. |
| Anion | Negative ion. |
| Ionic bond | Electrostatic attraction between oppositely charged ions. |
| Lattice | Regular repeating arrangement of ions. |
| Electrostatic force | Force of attraction between opposite charges. |
Avoid these mistakes
1
Saying ionic compounds conduct as solids — ions are fixed.
2
Saying electrons carry charge in molten ionic compounds — ions do.
3
Drawing shared pairs for an ionic compound — electrons are transferred.
4
Writing ion charges inside the brackets — they go outside at the top right.
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