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Flashcards in C4a Deck (10)
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1
Q

What did John Dalton do?

A
  • 19th century

- described atoms as solid sphere, and different spheres make different elements

2
Q

What did J J Thomson do?

A
  • 1897
  • concluding from his experiments that atoms weren’t solid spheres
  • his measurements of charge and mass showed that atoms must contain even smaller, negatively charged particles (electrons)
  • the theory was known as ‘plum pudding model’
3
Q

What did Ernest Rutherford do?

A
  • 1909
  • conducted famous gold foil experiment, firing positively charges particles at an extremely thin sheet of gold
  • expecting most particles to be deflected by positive ‘pudding’ that made up most of the atom
  • most particles passed straight through the gold atoms, very few deflected
  • he came up with a theory to explain this (theory of the nuclear atom)
  • tiny positively charged nucleus at the centre, surrounded by a cloud of negative electrons (most of the atom is empty space
4
Q

What did Niels Bohr do?

A
  • suggested electrons exist only in fixed orbits, or shells, and not everywhere in between
  • each shell has a fixed energy
  • his theory was supported by many experiments and helped to explain many other scientists observations at the time
5
Q

How do scientists back up their theories with evidence?

A
  • scientists do more experiments, get new evidence
  • nearly always leading to scientific knowledge developing (new evidence prompts people to come up with new, improved ideas)
  • these ideas can be used to make predictions, if proved right are good indication that the ideas are right
  • scientists put their ideas and research up for peer review (everyone gets to see new ideas, check for errors and then use it to develop their own work)
6
Q

What are the properties of an atoms nucleus?

A
  • middle of atom
  • protons and neutrons
  • positive charge because of protons
  • almost the whole mass of electron is concentrate in the nucleus
7
Q

What are the properties of electrons?

A
  • move around nucleus in electron shells
  • negatively charged
  • tiny, but cover lots of space
  • volume of orbit determines size of atom
  • virtually no mass
8
Q

What is the relation between protons and electrons?

A
  • number of protons equals number of electrons
  • the charge of electrons is the same as the charge of protons but opposite, so cancel each other out
  • making a neutral atom
9
Q

What is scientists realise about Rutherford’s model?

A

-the cloud of electrons around the nucleus of the atom would be attracted to the nucleus and cause the atom to collapse

10
Q

What are the properties of electrons, neutrons and protons?

A
  • protons are heavy and positively charged
  • neutrons are heavy and neutral
  • electrons are tiny and negatively charged