Atoms and elements

Atoms and elements

1. Atoms

   • Atoms have small nucleus surrounded by shells.
     • The nucleus
       • Protons
         • Protons have a positive charge
         • The mass of a proton is 1
       • Neutrons
         • Neutrons are neutral
         • The mass of a neutron is 1
       • The nucleus has a positive charge
     • The shells
       • Electrons
         • They move around the nucleus
         • They are negatively charged
         • They have a mass of nearly 0
       • They have an overall negative charge
     • Atoms have an overall neutral charge

2. Elements

   • Elements consist of one type of atom only
     • There are about 100 different elements and some haven't been fully discovered
   • Elements have no overall charge because they have the same amount of protons as electrons
     • If an electron is added or taken away the atom becomes charged and is then an ion
   • Different elements have different number of protons and electrons
   • The protons and electrons are equal to the atomic number
   • The neutron number is the atomic mass number - the atomic number
   • Potassium has: 19 protons and electrons. It has 20 neutrons because 39-19=20

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