Section 1- Principles of Chemistry (part 2)

Section 1- Principles of Chemistry (part 2)

1. Electron Shells

   • Nucleus
     • 1st Shell= 2 electrons
       • 2nd Shell= 8 electrons
         • 3rd Shell= 8 electrons
   • Atoms= happy when they're outer shell is full
     • Therefore they react with other atoms to complete their shells
   • Electronic configuration= 2,8,8 ect..

2. Ionic Bonding+ Ionic Compounds

   • ALL ATOMS WANT THEIR LAST SHELL TO BE FULL
   • If the atom only has 1 electron in its outer shell then it wants to get rid of it.
     • This atom would love to react with one with 7 in its outer shell because this one wants one more, there's too many to give away!
   • ion: "an atom or molecule with a net electric charge due to the loss or gain of one or more electrons"
   • Group 1 and 2 elements are metals and lose electrons to form +ve ions (cations)
   • Group 6 and 7 elements are non-metals and gain electrons to form -vs ions (anions)

3. Covalent Bonding+ Covalent substances

   • A covalent bond is a shared pair of electrons
   • Both atoms have a full outer shell and they are happy
   • Strong attraction between the shared electron pair and the nuclei of the atoms involved
   • Diamond+Graphite
     • Diamond=hardest substance in world! +makes 4 bonds per carbon atom
     • Graphite= Conducts electricity+makes 3 bonds per carbon atom

4. Balencing Equations

   • Word Equation= copper + oxygen = copper oxide
     • Symbol Equation= 2Cu + O2 = 2CuO
   • State symbols= Solid (s) Liquid (l) Gas (g) Aqueous (dissolved in water (a))
   • Practise Questions
   • You have to have the same amount of everything on either side of an equation or it will be sad

5. Isotopes and Relative Atomic Mass

   • An isotope is a different version of an atom
   • Carbon isotopes:
   • They have the same number of protons but a different number on neutrons
   • How to calculate relative atomic mass:
     • (mass of isotope x % abundance) + (mass of isotope x % abundance) ___________________________________________________________ 100
       • E.g. Boron= (11x80) + (20x10) ------------------ 100
         • = 10.8

6. Relative Formula Mass

   • Look at elements atomic mass on periodic table
     • Use the numbers to add up masses of formulas
   • E.g. MgCl2
     • Mg= 24
     • Cl= 35.5
     • 24+35.5+35.5= 95

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