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Atomic Structure

Proton -                                    Ions have different numbers of protons and electrons.

Relative Charge: +1             Isotopes - same element but a different number of neutrons.

Relative Mass: 1


Reltive Charge: 0

Relative Mass: 1


Relative Charge: -1

Relative Mass: 0      

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Atomic Models

In the 1800's John Dalton described atoms as solid spheres, and that different spheres made up different elements.

In 1897 JJ Thomson concluded that atoms weren't solid and indivisible. He discovered that atoms must contain smaller, negatively charged particles. He called these corpsucles (but we now call them electrons). His model was called the plum pudding model which was a positively charged sphere with negative electrons embedded in it.

In 1909 Rutherford conducted the gold foil experiment, it involved firing alpha particles at a very thin sheet of gold. According the plum pudding model most of the alpha particles should have been deflected but Rutherford found that most of them went straight through. This led to the nuclear model, a positive nucleus with electrons around it.

The Bohr model was another improvement as it showed that the electrons are in fixed shells with fixed energies, and the radiation has a fixed frequency.

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Groups 1 & 2 Alkali Metals

  • Weak bonds between atoms
  • React vigorously with water to form a metal hydroxide and hydrogen
  • The elements towards the bottom of the group are more reactive, because the one outer electron is further away from the positive nucleus, so the force needed to take the electron away is comparatively less than the elements toward the top of the group.
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