Chemistry C2

1. Chemistry C2 Revision PowerPoint - Big ideas Ionic and Covalent bondingMetallic structures

2. Covalent bonding In covalent bonding • non-metal atoms shareelectrons • simple molecules can form, or, giant covalent structures can form • a single covalent bond is a shared pair of electrons

3. Ionic bonding • In ionic bonding atoms transfer electrons, forming ions. • Positively and negatively charged ions attract each other in giant ionic lattices.

4. Ionic and covalent compounds • Ionic compounds form when metals react with non-metals. • Covalent compounds form when different non-metals react together

5. Drawing dot-cross diagrams • Dot-cross diagrams show the arrangement of electrons in ionic and covalent substances. The sodium ions, the chloride ions, the three hydrogen atoms and the nitrogen atom all have full outer shells of electrons, and are more stable in the compound than they were as separate elements.

6. Stable ions and molecules • Ions in ionic compounds and atoms in covalent compounds have stable electronic structures. • All outer electron shells are full

7. Ionic compounds - properties • Ionic compounds have high melting points and conduct electricity when molten or in solution.e.g. sodium chloride, NaCl

8. Metallic bonding • In metallic bonding, layers of closely packed ions are surrounded by a sea of delocalised electrons • Metals conduct electricity because their freely moving delocalised electrons • The properties of metals are altered by forming alloys – alloys are harder than pure metals because layers cannot form and slide