Everything Science Grade 10

CHAPTER 4. THE ATOM 4.6

possible for you to show this.

• Are there any ways in which our
  model could be improved?

Now look at what other groups have

done. Discuss the same questions for

each of the models you see and record

your answers.

Build an atom

See simulation: ( Simulation: VPcmk at http://www.everythingscience.co.za)

See simulation: ( Simulation: VPcph at http://www.everythingscience.co.za)

Chapter 4 | Summary

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

• Some of the scientists who have contributed to the theory of the atom includeJ.J.Thomson
  (discovery of the electron, which led to the Plum Pudding Model of the atom),
  Marie and Pierre Curie(work on radiation),Ernest Rutherford(discovery that posi-
  tive charge is concentrated in the centre of the atom) andNiels Bohr(the arrangement
  of electrons around the nucleus in energy levels).


• Because of the very small mass of atoms, their mass is measured inatomic mass units
  (u). 1 u= 1, 67 × 10 −^24 g.


• Therelative atomic massof an element is the average mass of all the naturally oc-
  curring isotopes of that element. The units for relative atomic mass are atomic mass
  units. The relative atomic mass is written under the elements’ symbol on the periodic
  table.


• An atom is made up of a centralnucleus(containingprotonsandneutrons), sur-
  rounded byelectrons. Most of the atom is empty space.


• Theatomic number(Z) is the number of protons in an atom.


• Theatomic mass number(A) is the number of protons and neutrons in the nucleus
  of an atom.

Chemistry: Matter and Materials 91