Chemistry Unit 2.1 - Structure and Bonding

Chemistry Unit 2.1 - Structure and Bonding

1. Compounds = Substances in which atoms of 2+ elements are chemically combined

2. Group 7 Elements - The Halogens

   • All react with metals (alkali) to form ionic compounds
     • The ions have a single negative charge
       • E.g. Chlorine forms Chlorine ions Cl-

3. Chemical Bonding = Transferring or sharing electrons in the outer shells of atoms (Ionic or covalent)

   • Ionic Bonding = When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions
     • The metal atoms give electrons to the non-metal atoms. Metal atoms = positive, Non-metal atoms = negative
     • Magnesium Oxide (MgO)
   • Covalent Bonding = Strong bond between 2 non-metal atoms, which consists of a shared pair of electrons
     • Dot and Cross Diagrams
     • Hydrogen Chloride (HCl)
     • Some covalently bonded structures contain simple molecules (HCl, H20, H2, Cl2) but others have giant covalent structures (Diamond and Silicon Dioxide)

4. Ionic substances form GIANT ionic lattices which contain oppositely charged ions

   • Have high boiling and melting points, and conduct electricity when dissolved in water or melted
   • Held together by strong electrostatic forces of attraction between positive and negative ions
     • Formed when a metal reacts with a non-metal
     • Example of an ionic lattice
       • NaCl (Na+, Cl-)

5. Group 1 Elements - Alkali Metals

   • All react with non-metal elements to form ionic compounds
     • The metal ion has a single positive charge
       • E.g. Sodium forms Sodium ion Na+

6. Electrons in the outer shell of atoms are DELOCALISED

   • They are free to move through the whole structure

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