Chapter 2: Chemical Principles

Vocabulary flashcards covering key terms and definitions from Chapter 2: Chemical Principles (atoms, elements, bonds, molecular concepts, and basic biochemical energetics).

Atom

The smallest unit of a chemical element; contains a nucleus of protons and neutrons with electrons orbiting around it.

Element

A pure substance made of one type of atom; defined by its atomic number (number of protons).

Proton

Positively charged subatomic particle located in the nucleus.

Neutron

Electrically neutral subatomic particle located in the nucleus.

Electron

Negatively charged subatomic particle that orbits the nucleus in electron shells.

Nucleus

Central core of an atom that contains protons and neutrons.

Electron shell

Region around the nucleus where electrons are found; shells have capacity limits (2, 8, 8, 18, …).

Atomic number

Number of protons in an atom; identifies the element.

Atomic mass

Total number of protons and neutrons in the nucleus; approximate mass of an atom.

Isotope

Atoms of the same element with different numbers of neutrons (e.g., 16O, 17O, 18O).

Ion

A charged atom formed by gaining or losing electrons.

Ionic bond

Bond between oppositely charged ions; result of electron transfer.

Covalent bond

Bond formed when two atoms share one or more pairs of electrons.

Polar covalent bond

Covalent bond with unequal sharing of electrons due to electronegativity differences.

Nonpolar covalent bond

Covalent bond with equal sharing of electrons.

Hydrogen bond

Attraction between a partially positive hydrogen attached to O or N and another O or N.

Van der Waals interactions

Weak attractions between molecules due to transient dipoles.

Molecular weight

Sum of the atomic weights of all atoms in a molecule.

Mole

A quantity equal to 6.02 x 10^23 particles; the amount of substance; its mass in grams equals its molecular weight.

Avogadro's number

6.02 x 10^23; number of particles in one mole.

Dalton

Unit of molecular mass; 1 Da is defined so that 6.02 x 10^23 daltons = 1 g.

Periodic table

Chart organizing elements by increasing atomic number and electron configuration.

Electronic configuration

Arrangement of electrons in the electron shells around the nucleus.

Electron shells capacity

First shell holds 2 electrons; second 8; third 8; fourth 18; etc.

Molecule

Two or more atoms held together by chemical bonds.

Compound

Substance composed of two or more different kinds of atoms.

Endergonic

Reactions that absorb energy.

Exergonic

Reactions that release energy.

Anabolism

Synthesis of larger molecules from smaller ones; e.g., amino acids to proteins.

Catabolism

Decomposition of complex molecules into simpler ones.

Synthesis (general)

Formation of a larger molecule from smaller components.

Decomposition

Breakdown of a molecule into smaller parts.

Exchange reactions

Reactions that are part synthesis and part decomposition; can be reversible.

Reversible reaction

A reaction that can proceed in either direction under certain conditions.

Electronegativity

Ability of an atom to attract electrons in a covalent bond.

Polarity

Unequal sharing of electrons in a covalent bond leading to partial charges.

Building blocks of carbohydrates

Monosaccharides.

Building blocks of proteins

Amino acids.

Building blocks of nucleic acids

Nucleotides.

ATP

Adenosine triphosphate; energy currency of the cell, powering cellular activities.

Most abundant elements in living organisms

Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S).