Topic 1

• Matter 


  anything with mass and occupies space (volume)
• Pure Substance 


  fixed and definite composition

  E.g. compound and element
• Element 


  pure substance made up entirely of one type of atom
• Compound 


  pure substances containing two or more elements chemically combined in a fixed ratio
• Mixture 


  contains 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


  no new substance is created and can be done as it does not involve changing the composition of a substance
• chemical change 


  substances being changed into a new substance and is irreversible
• atomic number 


  number of protons - represented by Z
• mass number 


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


  in the shell model of an atom, the electric configuration is a means of representing the number of electrons in each shell
• isotopes 


  are atoms with the same number of protons but different numbers of neutrons
• relative formula mass 


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

  it is calculated by adding RAM of atoms shown in the formula of the substance
• relative atomic mass 


  weighted average of the relative isotopic masses of an element on the scale where carbon-12 is taken as 12 units exactly; symbol A
• mass spectrometry 


  an instrument that measures 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 


  a vertical column of elements in the periodic table
• period 


  a horizontal row of elements in the periodic table
• core charge 


  of an atom is a measure of the attractive force felt by the outer electrons in the nucleus

  core charge = # of protons in nucleus - # of total inner shell electrons
• atomic radius 


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


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


  measured without changing the composition of the substance

  E.g. melting and boiling point, density and hardness
• chemical properties 


  involve change, describes the reaction that substances undergo