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General Science

General Science . 10/3/12. Warm-up. Make sure you have a book and have it opened to chapter 3 lesson 2. Objectives . Describe how electrons in an atom are arranged Explain how electrons fill the energy levels Explain how atoms combine to form compounds

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General Science

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  1. General Science 10/3/12

  2. Warm-up • Make sure you have a book and have it opened to chapter 3 lesson 2

  3. Objectives • Describe how electrons in an atom are arranged • Explain how electrons fill the energy levels • Explain how atoms combine to form compounds • Explain how ions form chemical bonds

  4. Arrangement of Electrons in an Atom • Electrons move around the nucleus • Each electron moves in its own space a certain distance from the nucleus. This is called the energy level.

  5. Energy Levels • Each energy level is labeled with a letter (p. 74) • Level K is the closet to the nucleus and is the smallest • Electrons in the outer energy levels have the most effect on the properties of an element

  6. Energy levels continued • Each energy level can hold only a certain number of electrons • The levels farther from the nucleus can hold more electrons than the levels closer to the nucleus

  7. How electrons fill energy levels • The electrons fill the energy levels in order • Level K is filled the first • Then L • This goes on until all the electrons are in place • Sodium example p.75

  8. How atoms combine • When atoms form compounds, they share, lend, or borrow electrons that are in their outer energy level • An atom has the tendency to fill its outer energy level • An atom becomes more stable when its outermost energy level is filled

  9. How atoms combine continued • An atom shares, lends, or borrows electrons to fill its outer energy level • Some atoms become more stable when they gain or borrow one electron from another atom

  10. Attraction between atoms • Example NaCl • P.76 • If the atom has more protons than electrons, it has a positive charge • If the atom has more electrons than protons, it has a negative charge • If an atom has equal protons and electrons it is said to have no charge

  11. Attractions between atoms • An atom that has either a positive or negative charge is called an ion • Positive and negative ions strongly attract each other • The attractive force between atoms is called a chemical bond • The chemical bond between ions holds the atoms together when they form a compound

  12. Assignment • Work on lesson 2 review (p.77)

  13. General Science 10/4/12

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