Vocab

• matter 


  anything with mass and occupies space
• pure substance


  fixed and definite composition and has an uniform composition (homogeneous)
• element 


  atoms that contains the same number of protons and made up entirely of pure substances
• compound 


  pure substance containing two or more elements chemically combined in a fixed ration
• mixture 


  contain two or more pure substances, physically combined in a variable ratio
• homogenous 


  uniform distribution of constituent substances
• heterogeneous 


  variable distribution of constituent substances
• physical change 


  do not involve the changing the composition of a substance - nothing new is created and can be undone
• chemical change 


  substance being changed into a new substance - cannot be reversed
• atomic number 


  number of protons - represented by Z
• mass number 


  number of protons and neutrons in the nucleus - represented by A
• electron configuration 


  shell model of an atom, represents the number of electrons in each shell
• isotopes 


  are atoms with the same number of protons but different number of neutrons
• relative formula mass (Mr)

  mass of one formula units of that compound compared to 1/12th of the mass of an atom of carbon -12

  calculated by adding RAM of atoms shown in the formula of the substance
• Mr Formula

  Mr(CO2) = 12.01 + 2(16.00)

  = 44.01
• relative atomic mass (Ar)

  weighted average of the relative isotopic masses of an element on the scale where 12C is taken as 12 units exactly

  mass of an atom of that element compared to the 1/12th the mass of an atom of carbon-12
• Ar Formula 


  Ar = (sum of (% abundance x Ar of each isotope)) / total percentage abundance
• mass spectrometry 


  instrument that measure the mass-to-charge ratio of particles
• valence electrons 


  an electron found in the valence shell; an outermost electron in an atom or ion
• group (periodic table) 


  a vertical column of elements in PT
• period (PT) 


  horizontal row of elements in PT

  start of new period corresponds to the outer electron of that element beginning a new shell
• core charge 


  measure of the attractive force felt by outer electrons to the nucleus

  core charge = #protons = # total inner shell electrons
• atomic radius 


  distance between the nucleus and the outer boundary of an atom
• ionisation energy 


  energy required to remove the outermost electron from one mole of gaseous atoms or ions in the gas phase