1.1 Atomic Structure

plum pudding model

atoms were a sphere of positive charge with small negative charged embedded within

electron shell model

atoms consisted of a small dense nucleus surrounded by orbiting electrons in shells (discovered by Rutherford in 1911). nucleus is positive as made of from protons and neutrons

relative mass of an electron

1/1840

mass number (A)

total number of protons + total number of neutrons

atomic number (Z)

number of protons

relative atomic/molecular/formula

the average mass of an atom/molecule/compound on a scale where an atom of carbon-12 is exactly12

isotope