CC3: Atomic substances

• What were Daltons ideas about the atom?


  
  

  • all matter was made of tiny particles called atoms (cant be broken down into simpler and are identical)
  • except the atoms of different elements are different from one another
  • during chemical reactions atoms rearrange to make different substances
• How and why did Daltons ideas about the atom change?

  Because of the discovery of subatomic particle.
• How are the subatomic particles arranged in an atom?


  Electrons orbit the nucleus in energy levels or shells. The nucleus contains protons and neutrons.
• how are atoms of a different element different?

  Different number of protons.
• what are the charges the three subatomic particles?

  Proton: +1

  Neutron: 0

  Electron: -1
• what are the relative masses of the three subatomic particles?

  Protons: 1

  Neutrons: 1

  Electrons: negligible
• why do atoms have no overall charge?

  It contains equal numbers of protons and electrons which have equal and opposite charges, this means that atoms are neutral overall.
• how does the size of the atom compare to the size of its nucleus?

  The nucleus is around 100,000 times smaller than the atom as most of an atom is empty space.
• where is most of the mass of an atom found?

  the nucleus
• what is the atomic number?

  The number of protons in an atom's nucleus.
• what is the mass number?

  The total number of protons and neutrons in an atom's nucleus.
• how does the number of electrons relate to the atomic number?

  They are equal
• how do you calculate the number of protons, neutrons and electrons using atomic and mass numbers?

  Protons: Atomic number Neutrons: Mass number - Atomic number Electrons: Protons (in a neutral atom)
• what is an isotope?


  An isotope is a variant of an element that has the same number of protons but a different number of neutrons in its nucleus.
• how do you identify isotopes from information about the structure of atoms?


  the atoms with the same number of protons but different number of neutrons are isotopes.
• why is the relative atomic mass of many elements not a whole number?

  The mass of the different atoms of an element including isotopes are averaged.
• how do you calculate the relative atomic mass of an element from the relative masses and abundances of its isotopes?

  Relative atomic mass=

  Isotope mass X isotope abundance /100