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Periodic Table Study Guide

Periodic Table Study Guide. How to Draw Lewis Structures. www.middleschoolscience.com 2008. Objective/Warm-up. SWBAT draw Lewis dot structures. How many valence electrons do each of the following elements have? Ca K O S C Br N. Groups - Review. Group 8 = 8 electrons.

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Periodic Table Study Guide

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  1. Periodic Table Study Guide How to Draw Lewis Structures www.middleschoolscience.com 2008

  2. Objective/Warm-up • SWBAT draw Lewis dot structures. • How many valence electrons do each of the following elements have? • Ca • K • O • S • C • Br • N

  3. Groups - Review Group 8 = 8 electrons Group 1 = 1 electron Except for He, it has 2 electrons Group 2 = 2 electrons • Each column is called a “group” 3,4,5,6,7 • Each element in a group has the same number of electrons in their outer orbital. • The electrons in the outer shell are called “valence electrons” www.chem4kids.com

  4. Lewis Structures • Find out which group (column) your element is in. • This will tell you the number of valence electrons your element has. • You will only draw the valence electrons. www.chem4kids.com

  5. Lewis Structures • Write the element symbol. • Carbon is in the 4th group, so it has 4 valence electrons. • Starting at the right, draw 4 electrons, or dots, around the element symbol. C

  6. Review-Octet Rule • Atoms bond in order to have 8 valence electrons. • Exception: • Hydrogen only needs 2 valence electrons to be complete.

  7. Rules for drawingLewis Dot Structures Example: CH2Cl2 C= 4 valence H=1 x 2 valence Cl=7 x 2 valence Total=20 valence • Count all the valence electrons for your atoms. • Draw the first atom (Second atom if the first is Hydrogen) listed in the center, then connect all other atoms to the center atom with single bonds. • Each bond counts as 2 electrons. • Complete any octets with remaining electrons. H H C Cl Cl

  8. Try these… • CH4 • NF3

  9. Double and triple bonds • What happens if you don’t have enough electrons? • Example: • CO2 • Make double or triple bonds.

  10. Try these… • OF2 • O2 • N2 • C2H6 • C2H4 • C2H2 • SO3

  11. Helpful Hints • Remember: your Lewis structure may contain multiple bonds (single, double, or triple) • When arranging your atoms, atoms are often written in the order in which they are connected in a molecule or ion (C is almost always your central atom; carbon forms 4 bonds)

  12. Examples Draw the dot structure: • H2O • CH3Br • CS2 • CH2O • O3

  13. Closure • Explain the steps to writing electron dot structures.

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