Physics - P4 Notes

The Atomic Model

• People used to believe that atoms were tiny spheres that couldn't be broken apart
• Rutherford and Marsden's experiments which disproved the plum pudding model consisted of firing alpha particles through gold foil. The particles that were deflected meant that there was a concentrated mass in the centre but it was mostly just empty space
• If an electron releases EM radiation, they move to a lower energy level that is closer to the nucleus
• James Chadwick provided evidence to suggest the existence of the neutron
• The nucleus makes up most of the mass of an atom
• The overall charge of an atom is positive
• If an atom loses one or more of its electrons it becomes positively charged

Nuclear Decay and Half-Life

• The mass number defines what element an atom is
• An atomic number is the number of protons and the…