Atomic Structure and the Periodic Table

• What are atoms?

  Smallest part of an element that can exist
• What do chemical symbols represent?

  An atom of an element
• How are compounds formed?

  By chemical reactions between elements
• What do chemical reactions involve when forming compounds?

  Formation of new substances and energy change
• What do compounds contain?

  Two or more elements chemically combined
• How can compounds be represented?

  By formulae using chemical symbols
• What is the formula for hydrochloric acid?

  HCl
• How can compounds be separated into elements?

  Only by chemical reactions
• What is a mixture?

  Two or more substances not chemically combined
• How do the chemical properties of substances in a mixture compare to those in a compound?

  They remain unchanged in a mixture
• What processes can separate mixtures?

  Filtration, crystallisation, distillation, chromatography
• What distinguishes the separation of mixtures from compounds?

  Mixtures use physical processes, compounds use chemical
• What was the first model of the atom?

  Atoms were thought to be tiny spheres
• What did the plum pudding model propose?

  Atom is a ball of positive charge with electrons
• What did the alpha particle scattering experiment conclude?

  Mass of an atom is concentrated at the nucleus
• What was observed in the alpha particle scattering experiment?

  Particles emerged at different angles
• Why were some alpha particles deflected in the experiment?

  Repelled by positive charge in the nucleus
• What did later experiments reveal about the nucleus?

  Positive charge can be subdivided into protons
• Who suggested that electrons orbit the nucleus?

  Neil Bohr
• Who provided evidence for neutrons in the nucleus?

  James Chadwick
• What is the atomic number?

  Number of protons in an atom
• How do atoms of a particular element compare?

  They have the same number of protons
• How do atoms of different elements differ?

  They have different numbers of protons
• Relative Charge

  Proton -> +1

  Neutron -> 0

  Electron -> -1
• What is the overall charge of an atom?

  0
• Why does an atom have an overall charge of 0?

  Because the number of protons equals electrons
• What is the approximate radius of an atom?

  0.1 nm
• How does the size of a nucleus compare to that of an atom?

  The nucleus is less than 1/10,000 of the atom
• What does the mass number represent?

  The sum of protons and neutrons
• What are isotopes?

  Atoms of the same element with different neutrons
• How is relative atomic mass defined?

  An average value considering isotope abundance
• How do you calculate the relative atomic mass of carbon with isotopes carbon-14 and carbon-12?

  Use the formula with their abundances
• What is the relative atomic mass of carbon given carbon-14 (20%) and carbon-12 (80%)?

  12.4
• What do electrons occupy in an atom?

  The lowest available energy levels
• What does the electronic structure of an atom indicate?

  How many electrons are in each shell
• What is the electronic structure of sodium?

  2, 8, 1
• What is the process to calculate relative atomic mass using isotopes?

  • Multiply each isotope's mass by its abundance
  • Sum the results
  • Divide by 100
• What are the key characteristics of isotopes?

  • Same element
  • Different numbers of neutrons
  • Affect relative atomic mass
• Relative Mass:

  Proton -> 1

  Neutron -> 1

  Electron -> very small
• How are elements arranged in the periodic table?

  By atomic number and similar properties