Modelling atoms

1
Modelling atoms

• by Awhina, Justine, Lapana and Luke

2
The problem

• We have learnt that everything is made of
• atoms. Miss Mitchell told us that more than
• 2000 years ago a Greek called Democrite
• put forward the idea that atoms are so small
• they are invisible and cannot be divided.
• How can we make a model of that?

3
Moving on

• Democrites idea was forgotten while people
• called alchemists tried to change ordinary
• metals like lead into gold.
• In 1869 a Russian called Mendeleev made a
• list of the different types of atoms. These are
• called elements such as oxygen, iron and
• copper.
• A table is not a model!

4
At last, something we can make

• When Ernest Rutherford first went to
• England he worked with J.J Thomson. In
• 1897 Thomson discovered that atoms can
• release electrons.
• That means, said Awhina that atoms are
• made up of smaller bits of matter.
• At last we can start making a model said
• Luke.

5
Our first model

• Thomson said electrons carried a negative charge
• and thought of the atom as being like a plum
• pudding or raisin bread.
• The plums or the raisins were the negative
• electrons. Lets make an edible model, said
• Lapana and Luke. Being boys, they liked their
• kai.
• Justine insisted it should be a raisin bread
  model,
• she disliked plums, they were sour tasting.

6
An edible model

• Ingredients
• 1 package active dry yeast
• 0.25 cup warm water
• 1 cup raisins
• 0.25 cup soft butter
• 0.25 cup sugar
• 1.5 teaspoons salt
• 0.5 cup scalded milk
• 3.75 cups all-purpose flour
• 2 eggs, beaten
• The result

7
A problem with our model

• Its gone! We were all guilty of having a slice,
  then another. How can you present a few crumbs as
  an atomic model?
• Luke saved the day. He suggested an A3 piece of
  paper and that we could put materials on it
  representing the electrons.
• I have just the idea, said Awhina milk bottle
  tops.

8
Thank you Awhina (and Fonterra)

• We glued the tops onto
• the paper with the heading
• Thomsons raisin bread
• model of the atom.
• Key
• represents the
• negative electron.
• We used just one colour.
• The area in the black circle represents the
  positive sphere.

9
Miss Mitchell, again

• That is a very good start said Miss Mitchell.
• Start? asked Lapana, speaking for the
• group.
• Yes a start, Miss Mitchell continued.
• Remember Ernest Rutherford, he went on
• in 1911 to make his own model of an atom.
• More models then said Justine. More food
• then said Luke hopefully.

10
Time out for research

• Ernests model was very different to the
• Greeks model. It was mainly empty space
• and was divided up. At the centre was a small
• nucleus with a positive charge (protons) and
• the electrons circled it. If the size of the
• nucleus was a tennis ball, the edge of the atom
• was about 600m way.

11
Our Rutherford model

• Justine suggested we scale down our model
• and not worry about the size of the electrons
• and nucleus.
• Lapana reminded us we would need different
• coloured tops for the protons and the
• electrons.
• Awhina said we could use circles to show the
• electrons moving round the nucleus.
• Luke stated that the model reminded him of
• planets orbiting the Sun.

12
Ara Rutherfords planetary model

• Key
• electron
• proton
• orbit path of electron

13
Challenges from the team

• Awhina how could you make a Rutherfords
• model that is 3D?
• Justine what materials could you use other
• than milk bottle tops?
• Lapana later models had electrons in shells,
• with 2 in the first shell and up to 8 in the
  second
• shell. Make a model of carbon with 6 electrons
• Luke I am interested in an edible model. What
• could be used for electrons and protons?

14
The last word from Miss Mitchell

• In Science models represent part of what is
• real about something. No single model can
• explain all the features.
• Models use something that is familiar to
• explain or describe something that is not
• familiar.