Molecular formulae: What are some compounds made up of?
small units called molecules - two or more atoms are held together by covalent bonds
Molecular formulae: What is the molecular formula?
the number of atoms of each element in a molecule
Empirical formula: What is the empirical formula?
the simplest whole-number ratio of atoms of each element in a compound
Empirical formula - What is the empirical formula important for?
substances that do not exist as molecules - this includes metals, and some non-metals (e.g. carbon - C, and silicon - Si)
Empirical formula - What do these substances form?
giant crystalline structures of atoms or ions
Empirical formula - What would it be impossible to base?
a formula on the actual number of atoms or ions as the numbers would go into billions and billions –> it would also vary depending on the size of the crystal
Empirical formula - Define the empirical formula in simple terms
the ratio of atoms or ions in the structure and they will always be the same
More relative masses - What do some compounds exist as?
simple molecules (e.g. water - H2O, and carbon dioxide - CO2)
More relative masses - What do other compounds exist as?
giant crystalline structures (e.g. all ionic compounds)
More relative masses - What are two terms needed for?
relative mass - one for simple molecules and another for giant structures
Relative molecular mass - What does relative molecular mass consist of?
it compares the mass of a molecule within the mass of an atom of carbon-12
Relative molecular mass - How can you easily calculate a relative molecular mass?
by adding together the relative atomic masses of the elements making up a molecule
