# Atoms and reactions

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• Atoms and Reactions
• Atomic Structure
• atomic number
• number of protons in the nucleus
• mass number
• number of particles (protons and neutrons) in the nucleus
• electrons
• 0 mass, 1- charge
• neutrons
• 1 mass, 0 charge
• protons
• 1 mass, 1+ charge
• Atomic masses
• relative isotopic mass
• mass of an atom of an isotope
• relative atomic mass
• weighted mean mass of an atom of an element
• (% abundance)/ 100 X mass number
• relative molecular mass
• weighted mean mass of a molecule
• relative formula mass
• weighted mean mass of a formula unit
• The mole
• amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12 isotope
• 6.02x10^23
• Types of formula
• Empirical formula
• 1) find the molar ratio of atoms
• 2) divide by the smallest number
• 3) write empirical formula
• 2) divide by the smallest number
• 3) write empirical formula
• Molecular formula
• 1) empirical formula
• 2) number of CH2 units in a molecule= Mr/empirical
• 3) molecular formula= no of units X CH2
• 2) number of CH2 units in a molecule= Mr/empirical
• 3) molecular formula= no of units X CH2
• Standard solutions
• 1) find the amount in mol
• 2) convert mols to grams=    m=n xM
• 2) convert mols to grams=    m=n xM
• Moles and reactions
• Reacting masses
• 1) work out amount in moles
• 2) compare against equations
• 3) m=n x M
• 2) compare against equations
• 3) m=n x M
• Reacting masses and gas volumes
• 1) amount in moles
• 2) compare against equations
• 3) V = n x 24
• 2) compare against equations
• 3) V = n x 24
• Water of crystallisation
• 1) amount in mol of anhydrous
• 2) amount in mol of water
• 3) determine ratio
• 2) amount in mol of water
• 3) determine ratio
• Titration calculations
• always work out amount in mol
• compare against equation
• use appropiate formula
• Oxidation numbers
• uncombined element = 0
• combined oxygen= -2
• combined hydrogen= +1
• simple ion = charge on ion
• combined fluorine = -1