Atomic Structure

Atomic Structure

1. Chemical Formulers and symbols

   • Chemical symbols are shortened versions of elements e.g H = Hydrogen
   • Chemical formulers are used to represent elements and compounds.
     • Balanced formulers are when the reactants and products are equal
   • word equations are equations with words of the elements
     • reactants -> Products.
     • In chemical reactions the products and reactants are equal in mass (same amount of atoms)
     • To balance a chemical equation keep adding until the reactants and products are equal

2. Compounds

   • compounds are substances of elements that are chemically bonded together
   • elements in compounds are in fixed proportions eg 12g of carbon every 32g of oxygen
   • NON-METAL COMPOUNDS: MON - 1, IDE - 2, TRI - 3

3. Atoms

   • All substances and elements are made out of atoms
   • Molecules are made of two atoms e.g I^2
   • Ions are made when an atom loses or gains an electron
     • ions in a formular must give an equal number of positive and negative charges
   • Radius = 1nm (1 x 10-10 M)
   • Radius of nucleus = 1 x 10-14 m
   • Protons (+ 1 charge) (1 mass) (neucleus)
   • Neutron (0 charge) (1 mass) (nucleus)
   • Electron (- 1 charge) (almost 0 mass) (electron shell)

4. History of the Atom

   • Plum pudding (Thomson)
     • ball of positive charge with negative electrons embedded into
     • Nuclear Model (Rutherford)
       • had a positive mass at the centre and is mostly empty space
         • Alpha scattering experement
           • gold foil, alpha particles (positive) fired at foil. most went though (mostly empty), as some repled, (positive mass)
       • Boar added electron shells that allowed electrons to orbit the nucleus
         • Chadwick discovered neutrons also resided in the nucleus

5. Periodic table

   • Mass number
     • Number of protons and neutrons in nucleus
     • on top
   • Atomic number
     • on bottom
     • amount of protons (number of electrons is the same)
   • Isotopes
     • same amount of protons but different number of neutrons
     • element - mass number e.g Carbon - 12 is carbon with mass 12
     • Chemical properties are the same. ELECTRONS DESIDE THE CHEMICAL PROPERTIES
     • Relative atomic mass
       • average weight of a elements isotopes
       • relative atomic mass of chlorine = 35.5 (2 different isotopes)
       • Calculating relative atomic mass
         • Ar = Total mass of atoms / total number of atoms
         • chlorine 35 = 75% chlorine 37 = 25%
           • every 100 chlorine 75 = chlorine 35, 25 = chlorine 37
           • (75x35)+(37x25) / (75 + 25)
             • 2625 + 925 / 100
               • 3550 / 100 = 35.5
       • average mass of atoms compared to 1/12 of a carbon-12 atom