Everything Science Grade 10

CHAPTER 12. THE PARTICLES THAT SUBSTANCES ARE MADE OF 12.1

Chapter 12 | Summary

See the summary presentation ( Presentation: VPdvy at http://www.everythingscience.co.za)

• The smallest unit of matter is theatom. Atoms can combine to formcompounds.


• Acompoundis a group of two or more different atoms that are attracted to each other
  by relatively strong forces or bonds. The atoms are combined in definite proportions.


• In a compound, atoms are held together bychemical bonds. Covalent bonds, ionic
  bonds and metallic bonds are examples of chemical bonds.


• Acovalent bondexists between non-metal atoms. Anionic bondexists between
  non-metal and metal atoms and ametallic bondexists between metal atoms.


• Covalent molecular structuresinteract and exist as separate molecules.


• Network structuresexist as giant repeating lattices. Network structures can consist
  of covalent, ionic or metallic compounds.


• A chemical formula is an abbreviated (shortened) way of describing a compound.


• Themolecular formulais a concise way of expressing information about the atoms
  that make up a particular covalent molecular compound. The molecular formula
  gives the exact number of each type of atom in the molecule.


• Theempirical formulais a way of expressing the relative number of each type of atom
  in a chemical compound. The empirical formula does not show the exact number of
  atoms, but rather the simplest ratio of the atoms in the compound.


• The structure of a compound can be represented by stick, ball-and-stick or space-
  filling models.


• Astickmodel use coloured sticks to represent compounds.


• Aball-and-stickmodel is a 3-dimensional molecular model that uses “balls” to rep-
  resent atoms and “sticks” to represent the bonds between them.


• Aspace-filling modelis also a 3-dimensional molecular model. The atoms are repre-
  sented by spheres.

Chapter 12 End of chapter exercises

1. Give one word or term for each of the following descriptions.

a. A composition of two or more atoms that act as a unit.

b. Chemical formula that gives the relative number of atoms of each

element that are in a molecule.

2. Give a definition for each of the following terms:

a. molecule

b. ionic compound

c. covalent network structure

Chemistry: Matter and materials 211