Atoms

Atoms

1. Elements

   • Protons
     • Positively charged
     • Part of the nucleus of an atom
   • Nuetrons
     • Neutral (has no charge)
     • Part of the nucleus of an atom
   • Electrons
     • Move around nucleus
     • Neagtively charged
     • Occupy the shells of an atom
   • Nucleus
     • In the middle of an atom
     • Contains protons and nuetrons
     • Has a positive charge overall

2. Periodic Table

   • Vertical columns are called groups
   • Elements in the same group have the same number of electrons in their outer shell
   • Bottom number is the atomic number
   • Top number is the mass number
     • total number of protons and nuetrons

3. Electron Shells

   • Lowest energy shells are always filled first
     • 1st = 2
     • 2nd = 8
     • 3rd = 8
   • Electrons always come in pairs
   • Atomic Structure is the number of electrons in each shell
     • Sulfur = 2,8,6
   • 4th shell not often used
     • Can hold 2 electrons

4. Compounds

   • Atoms joined together
   • Made up of multiple elements
   • If an atom shares an electron with another this a convalent bond
   • More free electrons = more reactive

5. Balancing Equations

   • Atoms can not be made or destroyed
   • Both sides of an equation must have equal number of each element
     • Number can only be added before compounds
   • Big number multiplied by smaller