Atomic structure

• What are atoms

  Building blocks of matter
• What do atoms have at there centre?

  Tiny dense nucleus
• What orbits the nucleus?

  Elections
• What does the nucleus contain?

  protons and neutrons
• What is the relative charge of protons?

  +1
• What is the relative charge of neutrons?

  0
• What is the relative charge of electrons?

  -1
• Relative mass of protons

  1
• Relative mass of neutron?

  1
• Relative mass of electron

  1/2000
• What do electrons orbit on?

  Energy levels
• How do electrons move up to a higher energy level?

  They absorb electromagnetic radiation
• What is the electron when it moves up an energy level?

  Unstable
• What will the electron eventually do?

  Move back down to its original energy level
• When the electron moves back down what does it emit?

  A wave of electromagnetic radiation
• What are isotopes?

  atoms with the same number of protons but different number of neutrons
• What is an ion?

  Is an atom or particle with a non-zero charge
• Which scientist discovered the electron?

  JJ Thomson
• What did he make?

  The plum pudding model
• What is the plum pudding model?

  Negatively charge electrons embedded into a ball of positive charge
• Plum pudding model diagram

  
• What is the alpha scattering experiment?

  It was when they directed a beam of positive alpha particles at a thin gold foil and expected the alpha particles to travel through the gold foil and maybe change direction a small amit
• Instead what did they discover?

  Most of the alpha particles passed straight through the foil

  Some of the alpha particles changed direction as it repelled the foil

  Few of the alpha particles bounced back off the gold foil
• What is the conclusion made when most of alpha particles passed through the gold foil?

  Atoms are mostly empty space
• What is the conclusion made when a few particles were deflected from their path but continued through the gold foil?

  The nucleus of the atom has a strong positive charge
• What is the conclusion made when a small number of alpha particles rebounded?


  The atoms contain a small , heavy nucleus
• What did Rutherford propose about the atom?

  The nuclear model of the atom
• What does the nuclear model contain?

  Nearly all of the mass of the atom is concentrated in the centre of the atom (nucleus)

  The nucleus is positively charged

  Negatively charged electrons orbit the nucleus at a distance
• Diagram of nuclear model v plum pudding model

  
• What does the Bohr model of the atom contain?

  Electrons orbit the nucleus at different distances

  The different orbit distance are called energy levels
• Bohr model diagram

  
• Successes of the Bohr Model

  Able to explain the findings from different experiments better than the nuclear model

  It was able to explain the process of absorption and emission of electromagnetic radiation
• When was the nuclear model improved?

  When the particles within the nucleus were discovered and Rutherford discovered it
• Who discovered the neutron?

  James Chadwick
• Difference between the Plum pudding and nuclear model table

  
• Why did the alpha particles bounce back during Rutherford's experiments?

  It repels because both the nucleus and alpha particle are positive
• What is process is radioactive decay?

  A random process and means it is not possible to know exactly when a particular nucleus will decay
• What are objects containing radioactive nuclei called?

  Sources of radiation
• What is the activity of a radioactive source defied as?

  The rate at which the unstable nuclei from a source of radiation decays
• What is this activity measured in?

  Becquerels(Bq)