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An atom it made up of three parts: Protons - neutrons - electrons.

An atom has same number of protons as electrons so atom has no electrical charge.

All atoms of a particular element have the same number of protons.

Atoms of different elements have different numbers of protons.


Proton: relative mass = 1, relative charge = +1

Neutron: relative mass = 1, relative charge = 0

Electron: relative mass = Very small, relative charge = -1

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  • Radioactive isotopes are atoms with unstable nuclei. May disintegrate and emit radiation.
  • This is radioactive decay.
  • Can result in formation of a different atom with different number of protons.


Alpha Decay - original atom decays by ejecting an alpha particle from the nucleus.

  • Alpha particle is a helium nucleus - particle made up of two protons and two neutrons.

Beta Decay - original atom decays by changing a neutron into a proton and an electron.

  • Newly formed high-energy electro ejected from nucleus, is a B decay.

Also Gamma - unlike alpha and beta, gamma emissions have no effect on structure of nucleus.

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Good work

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