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Covalent Bonding & Polarity

Covalent Bonding & Polarity. Chapter 6.2 . Chemical Bonding. Ionic Bond – Force that holds cations and anions together and which involves the transfer of electrons. Occurs between a metal and a nonmetal. Ionic Bonding.

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Covalent Bonding & Polarity

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  1. Covalent Bonding & Polarity Chapter 6.2

  2. Chemical Bonding • Ionic Bond – Force that holds cations and anions together and which involves the transfer of electrons. • Occurs between a metal and a nonmetal.

  3. Ionic Bonding • Elements achieve stable electron configurations by transferring or sharing electrons between atoms • Transferring Electrons - • Those with <4 valence electrons “LEND” them (Metals) • These elements “lose” valence electrons OR • Those with >4 valence electrons “BORROW” them (Nonmetals) • These elements “gain” electrons

  4. F F Chemical Bonding • What do you think will happen when 2 nonmetals bond? • Will there be a transfer of electrons? Why?

  5. Covalent Bonding • When two nonmetals meet - one atom is NOT strong enough to take electrons from the other! • So they must share them Covalent Bond! • Covalent bond - is a chemical bond in which two atoms shareone or more pairs of valence electrons.

  6. Covalent Bonding • Electrons want to be in pairs – 4 pairs of 2 to fulfill the octet rule. • Paired electrons are ‘happy’! • Unpaired electrons are ‘sad’

  7. Neon Fluorine Paired or Unpaired Paired Electron Unpaired Electron Happy! Sad!

  8. How it Works +

  9. F F How it works! Sharing Creates a Bond Outer Level  Still only hold 8!!!!

  10. F F F F Electron Configuration & Lewis Dot Structures • All 3 figures represent the same thing! • BAR = Bond of shared electrons F F

  11. This illustration shows four ways to represent a covalent bond between two hydrogen atoms. As a space shuttle lifts off, it leaves a water vapor trail. A reaction of hydrogen and oxygen produces the water.

  12. Covalent Bonds • Diatomicmeans “two atoms”. • Many nonmetal elements are often found as diatomic molecules. • Atoms of same element share bonding electrons equally. • Balanced

  13. F F F F Single Bond OR • Single Bond = • One Pair of e- Shared Between Two Atoms. • Each atom gives one e- to the shared pair Each atom now “Feels Like” it has 8 valence electrons!

  14. How Will These Two Bond? Oxygen and Oxygen O O

  15. O O O O Double Bond OR • Two Pairs of Electrons are Being Shared • Each atom gives one e- to each shared pair

  16. O O C Another example! Sharing Creates a Bond Since each are sharing two pairs  Double Bond! Carbon Dioxide CO2

  17. How Will These Two Bond? Nitrogen and Nitrogen N N N

  18. N N Triple Bond OR N N • Three Pairs of Electrons Being Shared

  19. Covalent Bonding Problems: Make a molecule out of Oxygen and two Fluorine

  20. F O F F Covalent Bonding Problems: F O Formula: OF2

  21. Covalent Bonding Problems: Try Carbon and two Oxygen

  22. Covalent Bonding Problems O O C O O C Formula: CO2

  23. Unequal Sharing of Electrons • Diatomic compounds share electrons equally. • Equal forces pulling on the shared electrons • What happens when atoms do NOT share electrons equally? • Unequal forces pulling on the shared electrons

  24. Unequal Sharing of Electrons Polar Covalent Bond: • Electrons not transferred from one atom to another, but… • Atom with greater attraction for electrons has a partial negative charge • Other atom has a partial positive charge. • Types of atoms determine whether a molecule is polar or non-polar.

  25. Unequal Sharing of Electrons • Electronegativity = Atom’s attraction for electrons • Bigger value  stronger attraction • Electronegativity trends (attraction for electrons): • Right side of periodic table: high • Exception for noble gases (Group #8A) - none • Left side of periodic table: low • Top of a group: higher • Bottom of a group: lower

  26. Prof Mokeur’s Periodic Table

  27. Unequal Sharing of Electrons • Shared electrons in a hydrogen chloride molecule spend less time near the hydrogen atom than near the chlorine atom.

  28. How to predict what type of bond will form between two atoms: • Non-polar covalent • Electronegativity difference is <0.5 • Polar covalent • Electronegativity difference is >0.5 and <2.0 • Ionic bond • Electronegativity difference is >2.0

  29. Examples • Boron and Hydrogen • Electronegativities: B = 2.0 H = 2.1 • Difference: 0.1  non-polar covalent • Potassium and Iodine: • Electronegativities: K = 0.8 I = 2.7 • Difference: 1.9  polar covalent • Sodium and Chlorine • Electronegativities: Na = 0.9 Cl = 3.0 • Difference: 2.1  ionic

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