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Unit 3

Unit 3. Valence Electrons and Ions. Subatomic Particles. In an atom Protons and neutrons are clumped together in a very small dense nucleus The Electrons are found outside of the nucleus in various electron clouds. Principle Energy Levels.

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Unit 3

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  1. Unit 3 Valence Electrons and Ions

  2. Subatomic Particles • In an atom Protons and neutrons are clumped together in a very small dense nucleus • The Electrons are found outside of the nucleus in various electron clouds

  3. Principle Energy Levels • The electron clouds are found at specific distances from the nucleus called Principle Energy Levels • Lowest energy levels are closest to the nucleus • Highest energy levels are farthest from the nucleus • Fill from Lower  Higher energy levels

  4. Energy Level ‘Clouds’ phycomp.technion.ac.il/~phr76ja/lecture1.html hoku.as.utexas.edu/.../a309f04/lect1cos.html

  5. Bohr • The Bohr model is used to show electron placements in the energy levels. • Elements in the same row of the periodic table have the same number of occupied energy levels

  6. Energy Levels First energy level- max 2 electrons Second energy level- max 8 electrons Third energy level- max 8 electrons Fourth energy level- max 18 electrons

  7. Valence Electrons • The electrons that occupy the highest energy level (or the outer shell) are called Valence Electrons • Valence electrons are important because they are the electrons involved in chemical reactions • This means that the number of valence electrons determines an element’s chemical properties

  8. Valence Electrons • Elements in the same column of the Periodic Table have the same number of valence electrons and have similar chemical properties.

  9. Ions • When elements undergo chemical reactions they either share or exchange electrons with other elements to fill their outer shells. • Atoms that have either lost or gained electrons are called ions. • Unlike neutral atoms, ions have a net charge.

  10. Ion Charges • The number of electrons that it has lost or gained determines an ion’s charge • Ions that GAIN electrons have a NEGATIVE charge and are called anions. • Ions that LOSEelectrons have a POSITIVE Charge and are called cations.

  11. Lithium Loses an Electron Li Li+1 Li Li+1 + 1 e-

  12. Fluorine gains an electron F F-1 F + 1 e- F-1

  13. Lithium Fluoride Li Li+1 + 1 e- F + 1 e- F-1 Li + F LiF

  14. HCl • Draw Bohr Models for Hydrogen and Chlorine and then show how they combine. H H+1 + 1 e- Cl + 1 e- Cl-1 H + Cl HCl

  15. Ion Drawings • Draw Bohr models for the following elements: • Oxygen • Sodium • Magnesium • Bromine

  16. Ion Drawings • In your lab groups draw Bohr models for the following elements: • Oxygen (2) • Hydrogen (2) • Sodium (1) • Chlorine (1) • Magnesium (1) • Calcium (1) • Bromine (2)

  17. Combine Ions • Cut out the circles and combine the Ions to make the following compounds. Draw arrows to show the movement of the electrons • H2O Water • NaCl Sodium Chloride • CaBr2 Calcium Bromide • MgO Magnesium Oxide

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