Atomic structure

Atomic structure

1. Fundamental particles

   • Protons
     • Charge +1
     • Mass 1
   • Neutrons
     • Charge 0
     • Mass 1
   • Electrons
     • Charge -1
     • Mass 1/1840

2. Key terms

   • Relative atomic mass, Ar
     • Average mass of 1 atom of an element divided by 1/12th mass of 1 atom of carbon 12
   • Relative molecular (formula) mass,Mr
     • Average mass of a molecule or a formula unit on a scale where an atom of carbon-12 is 12
   • Relative istopic mass
     • Mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12

3. Isotopes

   • Isotopes are atoms with the same number of protons but different numbers of neutrons.
   • Isotopes have similar chemical properties because they have the same electronic configuration/ the same number of electrons in the outer shell.
   • Their physical properties vary a little because they have different number of neutron/different masses.

4. an example of an element

   • 7 Li 3
   • mass number, A (top no. of an element) is the total number of protons and neutrons in the nucleus.
   • Atomic number,Z (bottom no. of an element) is the number of protons