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Introduction to Chemistry Bohr Models and Lewis Dot Structures

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

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Introduction to Chemistry Bohr Models and Lewis Dot Structures

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  1. Introduction to ChemistryBohr Models and Lewis Dot Structures

  2. Atoms • Basic unit of matter • Consists of: Electrons, Protons, & Neutrons

  3. 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

  4. 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

  5. Periodic Table of Elements I VIII +1 II 0 III IV V VI VII +2 +3 +/-4 -3 -2 -1 = element charges = Valence Electrons

  6. Periods and Groups • Periods go from left to right • Groups go up and down

  7. 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.

  8. Energy Levels • When two atoms approach each other their nucleus do not touch • Only electrons are involved in Chemical Reactions

  9. 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.

  10. 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

  11. Try the following elements on your own: • H • He • O • Al • Ne • K Bohr Diagrams P: N:

  12. Valence Electrons • Electrons that are found on the outer most energy level. This determines the elements chemical properties

  13. 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)

  14. 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 the2nd grouphave two valence electrons, and so on.

  15. Try the following elements on your own: • H • He • O • Al • Ne • K Lewis Dot

  16. More Practice

  17. Answers

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