Atomic Structure and Isotopes

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  • Created by: gracedean
  • Created on: 30-03-15 13:03
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  • Atomic structure and isotopes
    • Atoms contain three sub-atomic particles  called protons, neutrons and electrons. .
      • The protons and neutrons are found in the nucleus at the centre of the atom. The nucleus is very much smaller than the atom as a whole.
        • The electrons are arranged in energy levels around the nucleus.
          • Proton: Relative Mass =1 Relative Charge= +1
            • Neutron: Relative Mass=1 Relative Charge= 0
              • Electron: Relative Mass=almost zero Relative Charge= -1
      • The number of electrons in an atom is always the same as the number of protons, so atoms are electrically neutral overall. Atoms can lose or gain electrons. When they do, they form charged particles called ions
        • if an atom loses 1 or more electrons, it becomes a positively charged ion
          • if an atom gains 1 or more electrons, it becomes a negatively charged ion
    • Atomic Number and Mass number
      • The atomic number of an atom is the number of protons it contains.
        • All the atoms of a particular element have the same atomic number (number of protons). The atoms of different elements have different numbers of protons.
      • The mass number of an atom is the total number of protons and neutrons it contains. The mass number of an atom is never smaller than the atomic number. It can be the same, but is usually bigger.
      • The full chemical symbol for an element shows its mass number at the top, and its atomic number at the bottom.
        • You can work out the number of neutrons by subtracting the atomic number from the mass number
    • Isotopes
      • Isotopes are the atoms of an element with different numbers of neutrons. They have the same proton number, but different mass numbers.


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