Chapter 2: The Chemical Level of Organization

A complete set of vocabulary flashcards covering basic chemical principles, atomic structure, bonds, reactions, inorganic substances, and organic macromolecules from Chapter 2.

Matter

Anything that occupies space and has mass.

Mass

The amount of matter contained in an object; it does not change based on gravity.

Weight

An object's mass plus the effect of gravity on that mass, calculated in physics as $F = mg$.

Element

A pure substance that cannot be created or broken down by ordinary chemical means.

Compound

A substance composed of two or more elements joined by chemical bonds in fixed relative amounts.

Major Elements of the Human Body

Oxygen ($65.0\%$), Carbon ($18.5\%$), Hydrogen ($9.5\%$), and Nitrogen ($3.2\%$), which together account for approximately $96.2\%$ of total body mass.

Atom

The smallest quantity of an element that retains the unique properties of that element.

Proton

A positively charged subatomic particle found in the nucleus with a mass of $1\,\text{AMU}$ that determines the identity of an element.

Neutron

A neutral subatomic particle found in the nucleus with a mass of $1\,\text{AMU}$ that can be lost without altering the element's fundamental identity.

Electron

A negatively charged subatomic particle found orbiting outside the nucleus with a mass of $0\,\text{AMU}$ that participates in chemical bonding.

Atomic Number

The number of protons in the nucleus of an atom, which identifies the element and equals the electron count in a neutral atom.

Mass Number

The sum of protons and neutrons contained in the nucleus of an atom.

Anatomy of a Periodic Table Entry

A standard periodic table entry displaying the element's atomic number, atomic symbol, element name, average atomic mass, electron configuration, oxidation states, and state of matter at room temperature.

Isotope

An atom of an element that possesses a different number of neutrons than other atoms of the same element.

Hydrogen Isotopes

Isotopic variants of hydrogen, including Protium ($^1\text{H}$ with 0 neutrons), Deuterium ($^2\text{H}$ with 1 neutron), and Tritium ($^3\text{H}$ with 2 neutrons).

Radioactive Isotope

An unstable isotope whose nucleus readily decays, emitting subatomic particles and electromagnetic energy.

Half-life

The time required for half of any given sample size of an isotope to decay.

Ion

An atom or compound that carries an electrical charge due to an unequal number of protons and electrons.

Cation

A positively charged ion formed when an atom loses electrons, typically formed by metals.

Anion

A negatively charged ion formed when an atom gains electrons, typically formed by nonmetals.

Subatomic Particles Summary Table

A table summarizing subatomic particle properties: Protons ($+1$ charge, $1\,\text{AMU}$, nucleus), Neutrons ($0$ charge, $1\,\text{AMU}$, nucleus), and Electrons ($-1$ charge, $0\,\text{AMU}$, orbits).

Atomic Models

Visual representations of atomic structure, contrasting the planetary model (fixed electron orbits) with the electron cloud model (probability region of negative charge).

Electron Shell

A distinct region or layer around an atom's nucleus occupied by electrons at a specific energy level.

Valence Shell

The outermost electron shell of an atom, containing the valence electrons involved in chemical reactions.

Octet Rule

The principle that atoms tend to interact in ways that yield 8 electrons in their valence shell to achieve maximum stability.

Chemical Bond

An electrical attraction, weak or strong, that holds atoms together in close proximity.

Molecule

A group of two or more atoms held together by chemical bonds.

Ionic Bond

A chemical bond formed by the transfer of electrons between a metal and a nonmetal, creating oppositely charged ions that attract each other.

Covalent Bond

The strongest type of chemical bond, formed when two nonmetal atoms share valence electrons.

Nonpolar Covalent Bond

A covalent bond featuring equal electron sharing, resulting in an electrically neutral, hydrophobic molecule.

Polar Covalent Bond

A covalent bond featuring unequal electron sharing, producing partial positive ($\delta^+$) and partial negative ($\delta^-$) charges that make the compound hydrophilic.

Hydrogen Bond

A weak attraction between a weakly positive hydrogen atom bound to an electronegative atom and another nearby electronegative atom.

Kinetic Energy

The energy possessed by matter in motion.

Potential Energy

The stored energy matter possesses due to its position or chemical structure.

Chemical Energy

A form of potential energy stored in the chemical bonds of molecules.

Exergonic Reaction

A chemical reaction that net releases energy into its surroundings.

Endergonic Reaction

A chemical reaction that absorbs energy from its surroundings.

Synthesis Reaction

A chemical reaction where two or more substances combine to form a larger complex product, written as $A + B \rightarrow AB$.

Decomposition Reaction

A chemical reaction that breaks down a complex substance into smaller constituent parts, written as $AB \rightarrow A + B$.

Exchange Reaction

A chemical reaction combining synthesis and decomposition to exchange components between reactants, written as $AB + CD \rightarrow AC + BD$.

Catalyst

A substance that accelerates the rate of a chemical reaction without being consumed or permanently altered in the process.

Enzyme

A biological catalyst made of protein or RNA that lowers the activation energy required for a chemical reaction to occur.

Activation Energy

The initial input of energy required to start a chemical reaction.

Inorganic Compound

A substance that does not contain both carbon and hydrogen, such as water, salts, acids, and bases.

Acid

A substance that donates hydrogen ions ($\text{H}^+$) to a solution, maintaining a pH value below 7 (0 to 6).

Base

A substance that accepts hydrogen ions ($\text{H}^+$) in solution, maintaining a pH value above 7 (8 to 14).

pH Scale

A scale ranging from 0 to 14 measuring hydrogen ion concentration, where 0 to 6 is acidic, 7 is neutral, and 8 to 14 is basic.

Buffer

A solution of a weak acid and its conjugate base that resists changes in pH when acids or bases are added.

Organic Compound

A compound containing carbon and hydrogen, structured around a carbon skeleton formed by up to four covalent bonds per carbon atom.

Carbohydrate

An organic molecule composed of carbon, hydrogen, and oxygen in the general ratio $(CH_2O)_n$, serving as a primary cellular energy source.

Monosaccharide

A monomeric sugar unit classified by carbon count into hexoses (glucose, fructose, galactose) and pentoses (deoxyribose, ribose).

Disaccharide

A sugar formed by two monosaccharides joined by a glycosidic bond via dehydration synthesis, such as sucrose, lactose, and maltose.

Peptide Bond

A covalent bond formed between two amino acids through dehydration synthesis.

Amino Acid Structure

The structural building block of proteins, consisting of a central alpha carbon attached to a hydrogen atom, an alkaline amino group, an acidic carboxyl group, and a variable side chain ($\text{R}$).

Protein Structural Organization

The four architectural levels of a protein: Primary (sequence), Secondary (alpha-helix or beta-pleated sheet), Tertiary (3D folding), and Quaternary (assembly of multiple subunits).

Saturated Fatty Acid

A lipid chain containing no double bonds, fully saturated with hydrogen atoms, and solid at room temperature.

Unsaturated Fatty Acid

A lipid chain containing one or more double carbon bonds, creating kinks and maintaining a liquid state at room temperature.

Phospholipid

An amphiphilic molecule containing a glycerol backbone bound to two fatty acids and a phosphorus group.

Nucleotide Structure

A molecular subunit consisting of one or more phosphate groups, a pentose sugar (deoxyribose or ribose), and a nitrogen-containing base (purine or pyrimidine).

Adenosine Triphosphate (ATP)

A nucleotide compound composed of adenine, ribose, and three phosphate groups linked by high-energy bonds that drives cellular work.