Atomic Structure and The Periodic Table

Atomic Structure and The Periodic Table

1. Definitions

   • Element = A substance mad up of one type of atom
   • Compound
     • 2 or more elements that are chemically bonded together
   • Mixture
     • 2 or more elements or compounds that are combined with each other but not chemically bonded
   • Isotope - The same element (same protons) but a different number of neutrons

2. Structure of the Atom

   • Is a central positively charged nucleus made up of neutrons and protons
     • Surrounded by negative electrons that orbit the atom in shells
       • Shells = 2, 8, 8...
   • Mass Proton-1 Neutron-1 Electron-Negligible
     • Charge Proton-1 Neutron-0 Electron- -1

3. Periodic Table

   • Development
     • Dalton - Atomic Weight Order
       • Law of Octaves, properties repeat every 8 elements
         • Mendeleev - Switched elements to make the fit the pattern, left gaps for undiscovered elements and correctly predicted their properties
           • Modern - No Gaps, Noble gases, up to 118
   • Groups
     • 1
       • Alkali Metals
         • Reactivity increases as you move down group
           • Group 1 has 1 electron in outer shell, which it needs to lose to gain a noble gas structure, Further down the group means more shells so the outer electron is further away from the nucleus, so a weaker force of attraction on the electron from the nucleus, so less energy is needed to lose it and therefore react
         • All react vigorously with water in order to create an alkali solution
         • 1 electron in outer shell
     • 7
       • Halogens
         • React with non-metals to form a covalent compound
         • Reactivity increases and MP/BP decrease as you go up the group
     • 0
       • Noble gases - unreactive, BPs and MPs increase as you go down the group