Atomic structure and perodic table

• Whats an atom size?

  0.1 nanometres
• Facts about nucleus?

  Middle of atom

  Protons & neutrons

  radius of 1/10000 of radius of an atom

  Positive charge (because of protons)

  Almost whole mass of atom is concentrated in nucleus
• Facts about electrons?

  Move around nucleus in electron shells

  Negative charged and tiny, cover lots of space

  Volume of their orbits determines size of the atom

  Virtually no mass
• Why does an atom's proton number equal the electron number?

  Theres same number of protons and electrons, charge on each is the same size but opposite- cancel eachother out
• Whats an ion?

  Atom/group of atoms thats lost/gained electrons
• What does the nuclear symbol do?

  Tells you the atomic(proton number) & mass number
• Whats the atomic number?

  Tells you how many protons
• Whats the mass number?


  Total number of protons and neutrons in an atom
• Whats an element?


  Substance made up of atoms that have same number of protons in the nucleus
• What does an elements number of protons decide?

  What type of atom it is
• What are isotopes?

  Different forms of same element- same number of protons, different number of neutrons

  Same atomic number, different mass numbers
• Whats used to refer an element as a whole?

  Relative atomic mass (Ar)- Average mass, taking account of different masses and abundances (amount)
• Whats the relative atomic mass formula?


  Sum of (isotope abundance* isotope mass number)/sum of abundances of all isotopes
• What did John Dalton do?


  Described atoms as solid spheres, different spheres made up different elements in early 19th century
• What did J.J Thompson do?


  In 1897, concluded atoms weren't solid spheres, measurements of charge and mass showed atom contains smaller negative charged particles (electrons). This was the 'plum pudding model'
• What did the plum pudding model show?


  Ball of positive charge with electrons stuck in it
• What did Ernest Rutherford do?


  1909, him and student, Marsden conducted alpha particle scatering experiments, so came up with nuclear model
• What was the alpha particle scattering experiment?


  Fired positively charged particles at thin sheet of gold, from plum pudding model they expected the particles to pass straight through/slightly deflect

  Most particles did go straight through, some deflected more then thought and some deflected backwards

  Plum pudding model couldn't be right
• What was the nuclear model?

  Positively charged nucleus at centre, where most mass is concentrated

  Most of atom is empty space
• Why did Rutherford conclude most of atom is empty space?

  Because in the alpha particle scattering experiment, when alpha particles came near concentrated, +ve nucleus, they were deflected