Chemistry COVALENT BOND COVALENT COMPOUNDS CHAPTER 6 2
Chemistry COVALENT BOND & COVALENT COMPOUNDS CHAPTER 6. 2
2 Types of Chemical Bonds Ø Ionic Bond: ◦ transfer of electrons—full octet. ◦ Held together by electrostatic interaction. ◦ Between a metal and a non-metal Ø Covalent Bond: ◦ sharing of electrons (most electronegative element will pull electrons stronger). ◦ Full octet. ◦ Non-metals ◦ Covalent compounds also known as molecules.
Polar vs. Non-polar ØCovalent compounds are classified as polar or non -polar. ØIn polar bonds, electrons are shared unequally. The most electronegative element pulls electrons stronger. ØIn nonpolar bonds, electrons are shared equally by atoms because the elements have similar electronegativity.
Bond Type by Electronegativity— polar vs. non-polar Refer to pg. 161 for electronegativity values by element. ◦ Subtract the values for the 2 elements forming the bond. ◦ Non-polar: 0 -0. 2 ◦ Polar: 0. 3 -1. 7 (including 1. 7) ◦ Ionic: higher than 1. 7
Formation of a Covalent Bond Notice the sharing of electrons
Formation of a Covalent Bond
Formation of a Covalent Bond
Covalent Bonding § Bond energy – the energy required to break a chemical bond and form neutral isolated atoms. § Covalent compounds can have single, double, and triple bonds. § One covalent bond is made up of 2 electrons – Single bond § When atoms in a molecule share more than 2 electrons, they may have double or triple bonds. § Double covalent bond: formed by sharing 2 pairs of electrons (4 electrons). § Triple covalent bond: formed by sharing 3 pairs of electrons (6 electrons).
Multiple Bonds § Always between 2 non-metals sharing electrons. § Covalent compounds can have single, double, and triple bonds. § One covalent bond is made up of 2 electrons – Single bond § When atoms in a molecule share more than 2 electrons, they may have double or triple bonds. § Double covalent bond: formed by sharing 2 pairs of electrons (4 electrons). § Triple covalent bond: formed by sharing 3 pairs of electrons (6 electrons).
Octets in Elements ØHydrogen: only needs 2 electrons ØBoron: is happy with 6 electrons ØAlmost all other elements: 8 electrons
Electron Dot Notation
Writing Lewis Structures for molecules:
Writing Lewis Structures for molecules: 1. Determine number of valence electrons available. 2. Set up the skeleton of the molecule by placing least electronegative element in the middle, with the exception of hydrogen (Hydrogen is never a central atom because it can only form 1 bond). 3. Connect central atom to outer atoms by assigning 2 electrons in the middle of each pair. 4. Assign remaining electrons as lone pairs, ensuring each atom in the molecule has a full octet. 5. If missing electrons, you have double or triple bonds in the molecule.
Writing Lewis Structures for molecules:
Lewis Structures
Bond Strength Example: Compare the following molecules. Which molecule has the stronger NN bond? HNNH or H 2 NNH 2
Write the Lewis Structure for: Water Carbon dioxide A molecule of nitrogen
Write Lewis structures for the following polyatomic ions Ammonium Sulfate Phosphate
Diatomic Molecules ØElements form diatomic molecules to have a full octet. ØThe following elements are found in nature as diatomic molecules: ◦ Hydrogen (H 2), ◦ Nitrogen (N 2), ◦ Oxygen (O 2), and ◦ Halogens(F 2, Cl 2, Br 2, I 2).
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