Chapter Two

Atoms

Smallest unit of matter, building blocks of elements.

Protons

Positively charged particles in atomic nucleus.

Neutrons

Neutral particles found in atomic nucleus.

Electrons

Negatively charged particles orbiting the nucleus.

Atomic Number

Number of protons in an element's nucleus.

Atomic Mass

Total number of protons and neutrons combined.

Isotopes

Atoms with the same protons, different neutrons.

Radioisotopes

Unstable isotopes that emit energy.

Cations

Positively charged ions formed by losing electrons.

Anions

Negatively charged ions formed by gaining electrons.

Molecules

Two or more atoms bonded together.

Covalent Bonds

Atoms share electrons in outer orbitals.

Polar Covalent Bonds

Unequal sharing of electrons, creating charge differences.

Non-Polar Covalent Bonds

Equal sharing of electrons between atoms.

Ionic Bonds

Attraction between oppositely charged ions.

Hydrogen Bonds

Weak attractions between slightly charged atoms.

Molecular Shape

Three-dimensional arrangement of atoms in a molecule.

Hydrophilic

Molecules that dissolve easily in water.

Hydrophobic

Molecules that do not dissolve in water.

Amphipathic Molecules

Molecules with both polar and nonpolar regions.

Concentration

Amount of solute per liter of solution.

Acids

Substances that increase H+ concentration in solution.

Bases

Substances that decrease H+ concentration in solution.

pH

Measure of hydrogen ion concentration in solution.

Carbohydrates

Organic molecules composed of C, H, O.

Monosaccharide

Simplest form of carbohydrates, single sugar unit.

Disaccharide

Two monosaccharides bonded together.

Polysaccharides

Long chains of monosaccharides, complex carbohydrates.

Lipids

Hydrophobic molecules composed mainly of C and H.

Proteins

Composed of amino acids, essential for physiological processes.

Nucleic Acids

Molecules responsible for genetic information storage.

Nucleotides

Building blocks of nucleic acids, composed of sugar, phosphate, base.

DNA

Double helix structure, stores genetic information.

RNA

Single-stranded nucleic acid involved in protein synthesis.