Introduction to Chemistry Bohr Models and Lewis Dot Structures
Atoms Basic unit of matter Consists of: Electrons, Protons, & Neutrons
Atoms Review Consists of: Electrons, Protons, & Neutrons Electrons: particles orbiting around nucleus with a negative charge Protons: particles in the nucleus with positive charge Neutrons: particles in the nucleus with no charge
Element a pure chemical substance consisting of one type of atom Atomic Number= Number of Protons or Electrons Symbol Name Atomic Mass= Number of Protons + Number of Neutrons
Periodic Table of Elements VIII +1 II III IV V VI VII +2 +3 +/-4 -3 -2 -1 = element charges = Valence Electrons
Periods and Groups Periods go from left to right Groups go up and down
Bohr Models Proposed by Niels Bohr in 1915 Electrons orbit the nucleus in orbits that have a set size and energy. The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.
Energy Levels When two atoms approach each other their nucleus do not touch Only electrons are involved in Chemical Reactions
Bohr Diagrams Find out which period (row) your element is in. Elements in the 1st period have one energy level. Elements in the 2nd period have two energy levels, and so on.
Bohr Models RULE Show just electrons with energy levels 1st level holds 2 2nd holds 8 3rd holds 18 but is stable at 8 2-8-8 RULE!! Must fill an energy level to capacity before moving to the next energy level
Bohr Diagrams Try the following elements on your own: H He O Al Ne K P: N:
Valence Electrons Electrons that are found on the outer most energy level. This determines the elements chemical properties
Lewis Dot Structures Named after Gilbert Newton Lewis Show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule Show only valence electrons (outer energy level)
Lewis Dot Structures and Groups Find out which group (columns) your element is in. Elements in the 1st group have one valence electron. Elements in the 2nd group have two valence electrons, and so on.
Lewis Dot Try the following elements on your own: H He O Al Ne K
More Practice
Answers