P2- radioactivity

observing nuclear radiation

• nuclei of radioactive substances is unstable and they become stable by  radioactive decay- they emit radiation and turn into other elements
• three types of radioactive radiation- alpha, beta and gamma
• radioactive decay is a random process that isnt affected by external conditions
• background radiation is always around us- its from radioactive stuff in the environment, space and devises like x-ray tubes

discovery of the nucleus

• the plum pudding model- atoms are spheres made of positive charge with electrons stuck in them
• rtherford, geiger and marsden created the alpha particle scattering experiment- they fired alpha particles at thin gold foil
• most passed through- most of atom is empty space
• some were deflected by small angles- nucleus has positive charge
• a few rebounded- nucleus has a large mass and very large positive charge

nuclear reactions

• alpha decay- nucleus looses 2 protons and 2 neutrons which are emitted as alpha radiation
• beta decay- a neutron changes into a proton and a electron and the electron is instantly emitted as beta radiation
• relative mass of an electron= 0.0005
• if an atom gains or looses an electron is becomes charged and is called an ion
• all atoms of same element have same no. of protons but atoms of same element with different number of neutrons are clled isotopes
• when a nucleus emits an alpha particle the atomic number goes down by 2 and…