Module 2 - Foundations in chemistry

• What is the atom made up of?

  The atom consists of a tiny, dense nucleus that contains protons and neutrons. Electrons orbit the nucleus in shells (energy levels)
• What is the mass number?

  The number of protons and neutrons
• What is the atomic number?

  The number of protons (or electrons)
• What is an isotope?

  Atoms of an element with the same number of protons and electrons, but different number of neutrons
• Definition of relative isotopic mass:

  the mass of an atom of an isotope of an element relative to 1/12th the mass of an atom of carbon-12
• Definition of relative atomic mass:

  the weighted average mass of an atom of an element relative to 1/12th the mass of an atom of carbon-12
• How to work out the relative atomic mass:


  (mass x abundance) + (mass x abundance) / 100
• How can you find the Mr of a compound?

  By adding together all their Ar's (mass numbers)
• how do you work out the mols?

  Mols = mass / Mr
• How do you work out mols using avagadro's constant?

  Mols = number of particles / Avagadro's constant
• What is the empirical formula?

  the simplest whole number ratio of atoms of each element in a compound
• What is the molecular formula?

  The actual number of atoms of each element in a molecule