topic C1 (atoms)

topic C1 (atoms)

1. atoms

   • atoms contain protons neutrons and electrons
   • they have a radius of about 0.1 nanometers
   • all substances are made from atoms
   • they are really tiny and too small to see
   • the nuclear symbol of ab atom tells you its atomic (proton) number and mass number
   • atomic number=number of protons
   • mass number=number of protons+number of neutrons
   • number of neutrons=mass number-atomic number
   • atoms have no charge overall. they are neutral;
   • the electron charge is the same as the proton charge, but opposite - so they cancel out
   • in an ion, the number of protons doesn't equal the number of electrons

2. elements

   • an element is a substance made up of atoms that all have the same number of protons in their nucleus
   • elements are made up of atoms with the same atomic number
   • the smallest part of an element that you can have is a single atom of that element
   • the number of protons in the nucleus decides what type of atom it is

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