Overview
This lecture covers covalent bonding, the distinction between polar and non-polar covalent bonds, the special role of hydrogen bonds, and how these concepts connect to biochemistry.
Covalent Bonds
- Covalent bonds involve atoms sharing electrons rather than transferring them.
- Electrons spend equal time around both atoms in a typical covalent bond (e.g., two hydrogen atoms sharing electrons).
- Atoms may form multiple covalent bonds to fill their outer electron shells (valence shells).
- Hydrogen forms one bond, oxygen forms two, nitrogen forms three, and carbon forms up to four covalent bonds.
- Carbon is versatile, able to form single, double, and triple bonds with various nonmetals.
Types of Covalent Bonds: Non-Polar vs. Polar
- Non-polar covalent bonds have equal sharing of electrons between atoms.
- Polar covalent bonds involve unequal electron sharing, with electrons favoring one atom (e.g., in water H₂O).
- Polar molecules have regions of partial negative (more electrons) and partial positive (fewer electrons) charge.
Polarity and Water
- In water, oxygen is more electronegative (has more protons), so electrons spend more time near it, making it partially negative.
- Hydrogen ends up partially positive in water, creating molecular polarity.
- The bent shape of water is due to this polarity, affecting its properties as a solvent.
Hydrogen Bonds
- Hydrogen bonds are weak attractions between the partial positive hydrogen of one molecule and the partial negative oxygen of another.
- These bonds link separate molecules (not atoms within the same molecule).
- Hydrogen bonding gives water its unique properties like surface tension, cohesion, and solvent capabilities.
Comparing Bond Types
- Ionic bonds involve electron transfer between a metal and a nonmetal, creating ions.
- Covalent bonds involve electron sharing; can be non-polar (equal sharing) or polar (unequal sharing).
- Hydrogen bonds are weak bonds between molecules, caused by polarity.
Key Terms & Definitions
- Covalent Bond — a chemical bond where atoms share electrons.
- Non-polar Covalent Bond — equal sharing of electrons between atoms.
- Polar Covalent Bond — unequal sharing of electrons, creating partial charges.
- Electronegativity — an atom’s ability to attract shared electrons.
- Hydrogen Bond — weak attraction between partially charged regions of different molecules.
Action Items / Next Steps
- Review the summary table comparing bond types.
- Study the properties of water related to hydrogen bonding.
- Prepare for exploration of biomolecules in the next lecture/video.