Atomic structure

Atomic structure

1. Electrons

   • Orbit the nucleus in shells
     • A full outer energy shell is stable
     • Row on periodic table= no of electron shells
       • Group no on periodic table=no of electrons in OUTER SHELL
   • Charge -1, mass very small 1/1836
     • ATOMS of an element have the same number of protons and electrons
       • Atoms can gain or lose electrons to become IONS
         • Metal atoms lose electrons to become postitive ions-CATIONS
         • non-metal atoms gain electrons to become negative ions-ANIONS

2. The nucleus

   • Neutrons
     • Charge 0, mass 1
     • Number of neutrons=mass number-atomic number
   • Protons
     • Charge +1, mass 1
     • Number of protons=atomic number
     • Number of protons determines what element an atom is