C1.1 : Chemical Concepts

C1.1 : Chemical Concepts

1. The Atom

   • Nucleus
     • Middle of the atom
     • Protons (+ charge)
     • Neutrons (neutral charge)
     • Overall positive charge
   • Electrons
     • Move around the nucleus in fixed orbits
     • Negatively charged
     • Occupy shells around nucleus
     • Each shell has a fixed energy
   • Number of Protons= Number of electrons
   • Elements
     • consist of one type of atom only
     • ( number of protons in an atom decide what type of atom it is)

2. Periodic Table

   • Vertical columns=groups
   • Elements in the same group have the same number of electrons in their outer shells
   • Elements in the same group have similar properties
   • Element in the first column=group 0 (Noble gases)
   • Noble gases have full outer shells so they are stable
   • Mass number (top left) shows number of protons and neautrons
   • Atomic number (bottom left) shows number of protons

3. Electron Shells

   • Rules
     • Electrons ALWAYS occupy shells
     • The lowest energy levels are always filled first (ones closest to the nucleus
     • 1st shell= 2 electrons
     • Outer shells= 8 electrons
     • Atoms are stable and don't react when they have full outer shells
     • When the outer shell isn't full, atoms react to fill it
   • Electronic Structure
     • Work out number of electrons (same as Atomic number)
     • Work out how many electrons fill each shell (follow electron shell rules)

4. Compounds

   • Elements reacting and their atoms forming chemical bonds=Compounds
   • Making bonds= giving away, taking or sharing electrons
   • Only electrons are involved in bonding
   • Ionic Bonding
     • Compounds made of a metal and non-metal are made of ions
     • Metal atom LOSES electrons to make a positive ion
     • Non-metal atom GAINS electrons to make a negative ion
   • Covalent bonding
     • Compounds formed from non-metals consist of molecules
     • Atoms SHARE electrons to fill outer shells

5. Forces between Particles

   • Solids
     • Strong forces of attraction between particles=fixed positions=regular lattice arangement
     • Particles don't move so solids have a definite shape/volume
     • Particles vibrate-hotter solid means particles vibrate more so the solid expands
   • Liquids
     • Some forces of attraction between particles=they're free to move past each other but tend to stick together
     • Don't keep a definite shape and flow to fill bottom of container but keep same volume
     • Constantly (randomly) moving, hotter liquids expand
   • Gases
     • Next to no force of attraction between particles (travel in straight lines)
     • No definite shape or volume
     • Particles move randomly always. Expand when heated
   • Solutions
     • Mixture of solvent (liquid) and solute (solid)
     • Whether bond breaks depends on how strong the bonds are
     • Bonds break, molecules mix