# PHYSICAL CHEMISTRY

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• Atomic Structure
• Chemical properties of elements  depend on atomic structure and arrangement of electrons around nucleus
• Physical Chemistry
• Amount of substance
• relative atomic mass and relative molecular mass
• relative ATOMIC mass (Ar)
• carbon- 12
• is used as a baseline for relative atoimic mass - Mass spectrometer means  we able to measure masses of individuals istopes accuratley
• reative atomic mass is define as ................. Ar = average mass of an atom / 1/12 of 1 atom of C-12
• relative FORUMLA mass is used for ionic compounds because they don't exist as molecules. but have same symbol ( Mr)
• relative    MOCULAR  mass (Mr)
• defined as ......         Mr = average mass of an entity / 1/12 of 1 atom of C-12
• Carbon-12
• compare mass of a molecule with that of an atom of Carbon -12
• The mole and Avogradro constant
• defined as the number of atoms in 12g of Carbon-12
• actual number of atoms in 1g of hydrogen is huge and usually written as 6.022 x 10^23
• The mole
• the amount of substance that contains 6.022 x 10^23 particles
• to find moles
• mass/ Mr
• concentration x volume / 1000
• to find concentration
• number of moles / volume
• ideal gas equation
• PV = nRT
• n= moles
• V= volume
• R= gas constant
• P= pressure
• T = temperature
• Empirical formula
• is the simplest whole number ration of atoms of each element in a compound
• to find empirical formula
• 1. find masses of elements present            2. work out number of moles                3. convert No. of moles into a whole number ratio
• molecular formula gives the actual number of atoms of each element of the compound
• Mr/ mass of empirical  formula
• Blanced eqations and assoiciate equations
• balanced equations
• Make sure there are the same number reactants and products on each side
• ionic equations
• 1.write out equation         2. note which ions are present          3. rewrite equation with ions               4. get rid of that appear on both sides - these arte spectator ions
• Atom economy
• mass of desired product / total mass of reactants x 100
• percentage yield
• the number of moles of a specified product / theoretical maxium number of moles of the product x 100
• Chemists use amount of a subatnce in moles because one mole of a subatnce always contains same number of entiites of the substance
• Arrangement  of electrons in orbritals linked to the way in which elemnets are orgsnised in periodic table
• Measure mass of atoms using mass spectrometer
• Fundamental particles
• Protons
• Charge = +1
• Mass = 1
• Electrons
• Charge = -1
• Mass = very small
• Neutrons
• Charge= no charge
• Mass = 1
• Carbon - 12
• Chosen as its mass  per nucleon is around average
• Therefore an atomic mass unit is defined as 1/12th of the mass of one atom of Carbon-12
• Mass number and isotopes
• Atom is named after number of protons in nucleus
• The number of protons in the nucleus of an atom is called the ATOMIC NUMBER
• It has the symbol Z
• The MASS NUMBER is the sum of protons and neutons in neuclus of atom
• it has the symbol A
• ISOTOPES  are atoms with the same atomic number but different mass numbers
• They therefore differ in relative atomic  mass but have same chemical properties
• Time Of Flight (TOF) Mass Spectrometer
• it can be used to:                     find the abundance and mass of each isotope in an element allowing us to determine relative atomice mass...
• .....And find the relative molecular mass of substances made from molecules
• stage 1
• Ionisation
• Electronspray
• sample dissolved in a volatile solvent. injected into mass spectrometer
• Particles are ionised by gaining a proton from electron spray
• Its used for   substances with higher molecular mass
• stage 2
• Acceleration
• Positive ions are then accelerated using electric field to give them all the same kinetic energy
• Lighter particles have a faster velocity and heavier particle have a slower  velocity
• Stage 3
• Flight  tube ( ion drift )
• Ions travel through hole in the negatively charged plate into a ube
• TOF of each paricle depends on its velocity and therefore mass
• Stage 4
• Detection
• + Ions hit - charged electric plate. the + ions are discharged by gaining electrons from the plate
• This generates a movement of electrons and an electric current is measured
• it can be used to identify elements and determine relative molecular mass
• Gives accurate information about relative isotopic mass and also the relative abundance of isotopes
• electron configuration
• FIRST IONISATION ENERGY  Is the energy required to remove one mole of the most loosely held electrons from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of +1
• The maximum No. of electrons in each shell are:
• Shell 1 :
• shell 2:
• shell 3:
• Sub shells
• D: 10 electrons
• P: 6 electrons
• F: 14 electrons
• S: 2 electrons
• Orbitals
• S orbital
• P orbitals
• ionisation energies
• SECOND IONISATION ENERGY bigger than 1st - when 1st electron is removed a + ion forms - increases attraction between remaining electrons so energy reuired to remove nexdt electron is larger
• Chosen as its mass  per nucleon is around average
• Therefore an atomic mass unit is defined as 1/12th of the mass of one atom of Carbon-12