GCSE science <3

• J.J Thomson discovered the plum pudding model of the atom
• Rutherford's experiment discovered that the atom is mostly empty space and that the nucleus must be positively charged
• The plum pudding model is a positively charged sphere with negative electrons embedded into it
• In the plum pudding model, the charge and mass are evenly distributed throughout the whole structure
• The mass number is the total number of protons and neutrons in an atom.
• The atomic number is the number of protons (and electrons) in the nucleus of an atom.
• Electrons are found in orbit around the nucleus
• Electrons have a very small mass and a charge of -1
• Protons and neutrons are found in the nucleus of an atom.
• Neutrons have a mass of 1 and no charge
• Protons have a mass of 1 and a charge of +1
• Number of neutrons = mass number - atomic number
• An atom is neutral - The positive charges of the protons and negative charges of the electrons will cancel out
• Number of protons = 4

  Number of neutrons = 5

  
• (d) Freezing

  (e) Evaporation

  
• The existence of neutrons was discovered by James Chadwick
• The total positive charge in every atom of an element is always the same because positive charge is provided by protons
• Isotopes of the same element will have the same atomic number and a different relative atomic mass
• • 1st Shell - 2 electrons
  • 2nd shell - 8 electrons
  • 3rd shell - 8 electrons
• Electron shells fill across a period (the horizontal row on the periodic table)
• A vertical column on the periodic table is called a group
• A horizontal row on the periodic table is called a period
• The common thing about elements in the same group is that they have the same number of electrons on the outer shell
• The common thing about elements in the same period is that they have the same amount/number of shells