Flashcards
Section 1 - Chemical concepts
Cards in this deck (16)
- 1What is an atom?An atom is a tiny particle of matter (stuff that has mass). Atoms make up everything in the universe.
- 2Who described atoms as solid spheres at the start of the 19th century?At the start of the 19th century John Dalton described atoms as solid spheres and said that different spheres made up the different elements.
- 3Who concluded from his experiments in 1897 that atoms were not solid spheres?J J Thomson concluded from his experiments in 1879 that atoms were not solid spheres. His measurements of charge and mass showed that atoms must contain even smaller negatively charged particles - electrons.
- 4Describe the plum pudding model of the atom.In the plum pudding model of the atom, most of the atom consists of positively charged "pudding" and there are tiny electrons in the pudding.
- 5Who showed that the plum pudding model was wrong?Ernest Rutherford and his students Hans Geiger and Ernest Marsden conducted the 'gold foil experiment' that showed the plum pudding model to be wrong.
- 6What was the gold foil experiment?The gold foil experiment was first conducted in 1909. Positively charged particles were fired at a thin sheet of gold.
- 7What were the results of the gold foil experiment?It was predicted by Rutherford that the positively charged particles would be repelled by the "pudding" of the gold atoms. In fact, most of the particles passed straight through the gold atoms and a very small number were deflected backwards.
- 8Describe the theory of the nuclear atom.In the theory of the nuclear atom there is a tiny, positively charged nucleus at the centre, surrounded by a 'cloud' of negative electrons - most of the atom is empty space.
- 9What was the problem with electrons in a 'cloud' around the positively charged nucleus as Rutherford described?The electrons would be attracted to the nucleus causing the atom to collapse.
- 10How does the Bohr model differ from the the theory of the nuclear atom?In the Bohr model the electron exist in fixed orbits or shells, and nowhere inbetween.
- 11Niels Bohr suggested that electron shell had a fixed ____.Energy.
- 12The nucleus1) It's in the middle of the atom.
2) It contains protons and neutrons.
3) Protons are positively charged.
4) Neutrond have no charge (they're neutral)
5) So the nucleus has a positive charge.
6) It's tiny compared with the rest of the atom. - 13The electrons1) They move around the nucleus.
2) They're negatively charged.
3) They're tiny, but they cover a lot of space.
4) They occupy shells around the nucleus.
5) These shells explain the whole of Chemistry - 14The number of protons is always equal to the number of what in the atom?The number of protons is always the same as the number of electrons, because their charges are the same size but opposite and an atom is neutral. If any electrons are added or removed the atom becomes charged and is then an ion.
- 15The number of what in an atom decide what type of atom it is?Protons
- 16—
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- Year 9 Chemistry Flashcards on Section 1 - Chemical concepts, created by Tom Hahn on 22/08/2016.
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- Tom Hahn
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