Glossary
Covalent Bonds
Strong chemical bonds formed when two atoms share one or more pairs of electrons, creating stable molecules.
Example:
In a water molecule (H₂O), oxygen and hydrogen atoms are held together by covalent bonds where electrons are shared.
Dehydration Synthesis
A chemical reaction that builds polymers from monomers by removing a molecule of water, often requiring energy and enzymes.
Example:
When your body builds muscle, amino acids are linked together into proteins via dehydration synthesis reactions.
Double Bond
A type of covalent bond where atoms share two pairs of electrons, represented by a double line between atomic symbols.
Example:
The oxygen atoms in an O₂ molecule are connected by a double bond, allowing them to share two pairs of electrons.
Electronegativity
A measure of an atom's ability to attract and hold onto electrons within a chemical bond.
Example:
Oxygen has a high electronegativity, which is why it strongly pulls electrons towards itself in a water molecule.
Hydrogen Bonds
A specific type of weak intermolecular attraction between a hydrogen atom (covalently bonded to a highly electronegative atom like O, N, or F) and another electronegative atom on a different molecule.
Example:
Hydrogen bonds are crucial for holding the two strands of a DNA double helix together.
Hydrolysis
A chemical reaction that breaks down polymers into monomers by adding a molecule of water, often releasing energy and requiring enzymes.
Example:
During digestion, complex carbohydrates are broken down into simpler sugars through hydrolysis reactions.
Intermolecular Bonds
Weaker attractive forces that occur *between* separate molecules, influencing a substance's physical properties.
Example:
The attraction between individual water molecules, which causes water's high surface tension, is due to intermolecular bonds.
Intramolecular Bonds
Strong chemical bonds that hold atoms together *within* a single molecule.
Example:
The covalent bonds connecting carbon and oxygen atoms in a CO₂ molecule are intramolecular bonds.
Ionic Bonds
Chemical bonds formed by the electrostatic attraction between oppositely charged ions, which result from the complete transfer of electrons between atoms.
Example:
Table salt, sodium chloride (NaCl), is formed by ionic bonds where sodium donates an electron to chlorine, creating charged ions that attract.
Metallic Bonds
Chemical bonds found in metals, characterized by a 'sea' of delocalized electrons shared among a lattice of positively charged metal ions.
Example:
The excellent electrical conductivity of copper wires is due to the free-moving electrons in its metallic bonds.
Monomers
Small, single molecular units that can be linked together to form larger polymer chains.
Example:
Amino acids are the monomers that link together to form long protein chains.
Nonpolar Covalent Bonds
Covalent bonds where electrons are shared equally between two atoms due to similar electronegativity values, resulting in no partial charges.
Example:
The bond between two carbon atoms in a hydrocarbon chain is a nonpolar covalent bond because they have very similar pulls on the shared electrons.
Polar Covalent Bonds
Covalent bonds where electrons are shared unequally between two atoms due to a significant difference in electronegativity, creating partial positive and negative charges.
Example:
The bonds between oxygen and hydrogen in a water molecule are polar covalent bonds, making water a polar molecule.
Polymers
Large molecules (macromolecules) composed of many repeating smaller units called monomers, linked together by covalent bonds.
Example:
Starch, a complex carbohydrate, is a polymer made up of many glucose monomers linked together.
Single Bond
A type of covalent bond where atoms share one pair of electrons, represented by a single line between atomic symbols.
Example:
The bond between two hydrogen atoms in an H₂ molecule is a single bond, sharing just one electron pair.