EL 1 

Atoms containing-

• Positive proton with mass 1 and charge 1 found in nucleus
• Neutral neutrons with mass 1 and charge 0 found in nucleus
• Electrons with mass 0 and charge -1 found around nucleus
  ==Mass number== = number of protons + number of neutrons in an atom
  ==Atomic numbe==r = number of protons in an atom

{{The history of the atom{{

• ==Dalton==- created the KS3 model of a partial
• ==Thomson==- found evidence for the electron, used the plum pudding model describing negative electrons embedded in a ball of positive charge
• ==Rutherford-== created the nuclear model describing negative electrons orbiting a positive nucleus
• ==Moseley==- in 1913 determined charges on nuclei allowing the periodic table to be arranged in order of atomic number instead of atomic mass
• ==Bohr==- in 1914 created a nuclear model with clearly defined orbits. The energy released when electrons fall from one shell to another is given out in an emissions spectrum
• ==Chadwick-== in 1932 Chadwick found evidence for partials in the nucleus with a mass but no charge to he discovered neutrons