GCSE Chemistry (AQA)

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Electronic Structure

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Atomic structure and the periodic table A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

Electronic Structure

7:45 Electron Energy Levels of Atoms
Spec 4.1.1.7
Previous Relative Atomic Mass Next Periodic Table Structure
  • Electrons are found in shells around the nucleus.
  • Atoms have a basic structure with a central nucleus made of protons and neutrons.
  • Electrons are arranged in shells (energy levels) around the nucleus.
  • The innermost shell has the lowest energy level, closest to the nucleus.
  • Energy levels increase moving outwards from the nucleus.
  • Each shell can contain a certain number of electrons: first shell (2), second shell (8), third shell (8).
  • Argon atom example: first shell (2 electrons), second shell (8), third shell (8).
  • Electrons fill the shell with the lowest available energy level first.
  • Beryllium atom example: 4 electrons, first shell (2), second shell (2).
  • Sodium atom example: 11 electrons, first shell (2), second shell (8), third shell (1).
  • Electron structure refers to the arrangement of electrons in an atom.
  • Electron structure can be written as numbers or shown on a diagram using dots and crosses.
  • Beryllium's electronic structure: 2, 2.
  • Sodium's electronic structure: 2, 8, 1.
  • Diagrams can use dots or crosses to represent electrons.
  • Magnesium example: atomic number 12, 12 electrons, first shell (2), second shell (8), third shell (2).
  • Ensure correct number of electrons in each shell and overall.
  • Be comfortable figuring out electron structures for the first 20 elements in the periodic table and elements in group one and seven.

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