C1.2 Flashcards

1
Q

Describe the difference between an atom and a molecule

A
  • An atom is the smaller particle of an element that still has its chemical properties. Different elements are made from different atoms.
  • A molecule is made from two or more atoms join together. They are joined by attractive forces called chemical bonds.
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2
Q

Describe what is inside of an atom

A
  • Atoms contain mainly empty space, but they do have three even smaller subatomic particles.
  • protons and neutrons are joined together as the nucleus at the centre.
  • electrons are surrounding the nucleus in shells.
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3
Q

How do you find the number of protons neutrons and electrons.

A

Protons = atomic number
Electrons = Protons
Neutrons = Atomic mass - atomic number

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4
Q

What is an isotope?

A

Isotopes are forms of the same element with the same number of protons and electrons, but different number of neutrons.

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5
Q

What are ions?

A

Ions are charged particles. They are formed when atoms, or groups of atoms, lose or gain electrons.

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6
Q

What did Dalton do?

A
  • In 1803, John Dalton suggested that all matter is made from atoms.
  • he believed that all atoms of an element are identical, and that different elements contain different types of atoms.
  • he imagined atoms as tiny solid balls.
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7
Q

What did Thomson do?

A
  • Joseph John Thomson discovered the first subatomic particle, the electron is 1897.
  • Thomsons model of the atom had to make sense of two observations: atoms contain electrons, and atoms are neutral overall.
  • In his plum pudding model, he suggested that atoms are spheres of positive charge with electrons spread out randomly inside
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8
Q

What did Rutherford do?

A

In 1909, Ernest Rutherford, hans Geiger and Ernest Marsden conducted an experiment which pointed beams of positively charged alpha particles at thin gold foil.
- Some atoms changed direction slightly, and some even came straight back. Rutherford explained the results by suggesting that an atom has a positively charges nucleus containing most of its mass. He also said that outside the nucleus, electrons orbit like planets in a solar system.

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9
Q

What did Bohr do?

A
  • Niels Bohr realised that orbiting electrons would attracted to the oppositely charged nucleus and would rapidly spiral inwards.
  • In 1913 he used mathematical models to improve Rutherfords model.
  • He showed that electrons occupy fixed energy levels, or shells, around the nucleus.
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