Atoms

Atoms

1. Atomic Structure

   • The Atom
     • The atom is the smallest part of an element ehich can take part in a chemical reaction
     • sub-atomic particles
       • protons
         • +1 charge
         • in the nucleus
         • 1 AMU
       • neutrons
         • 0 charge
         • in the nucleus
         • 1 AMU
       • electrons
         • -1 charge
         • orbiting the nucleus
         • 0 AMU
   • Atomic Numbers and Mass Number
     • Atomic number is the number of protons (or electrons) in an atom of an electron
     • Number of protons = Number of electrons
     • Mass number is the number of protons and neutrons in an atom of an element
     • arrangement of electrons is called electronic configuration
   • The Bohr Structure
     • Electrons represented in dots
     • The first shell holds two electrons and the rest hold up to eight
   • Isotopes
     • Isotopes are atoms of the same element which have the same atomic number but different mass numbers
       • same number of protons, different number of neutrons

2. Forms of Atoms

   • All substances are made up of atoms
   • Elements are substances made up of only one type of atom
   • Molecules are made up of two atoms chemically combined
     • Hydrogen gas has chemical formula H2
       • hydrogen atoms not stable on their own
         • pair up into molecules
       • Oxygen
         • O2
       • Nitrogen
         • N2
       • Chlorine
         • Cl2
   • Compounds are made of two or more elements chemically combined
     • formed when atoms/molecules react with each other in order to become more stable
     • The properties of a compound differ from those of the elements from which it is made
   • Mixtures contain two or more different substances mingled together but not chemically combined
     • easily separated
     • air
       • mixture if gasses
     • sea water
       • water and salts
     • alloys
       • mixture of metals