Atoms, Ions, and Molecules Flashcards

Vocabulary flashcards covering key terms and definitions from Chapter 2 lecture notes on atomic structure, ions, chemical bonds, water properties, mixtures, pH, buffers, and biological macromolecules.

Matter

Anything in the universe that has mass and occupies space, existing in solid, liquid, or gas forms.

Atom

The smallest particle that exhibits the chemical properties of an element.

Neutron

An uncharged subatomic particle located in the nucleus of an atom with a mass of one atomic mass unit ($\text{amu}$).

Proton

A subatomic particle located in the nucleus of an atom with a positive charge of $+1$ and a mass of one atomic mass unit ($\text{amu}$).

Electron

A subatomic particle with a negative charge of $-1$ and a mass of $1/1800\text{th}$ of a proton or neutron, located in electron orbitals at varying distances from the nucleus.

Atomic Number

The number of protons in an atom of an element, located above the chemical symbol on the periodic table.

Average Atomic Mass

The mass of both protons and neutrons in an atom, displayed below the chemical symbol on the periodic table.

Isotopes

Atoms of the same element that have the same number of protons and electrons but a different number of neutrons.

Radioisotopes

Chemically unstable isotopes containing excess neutrons that emit radiation as they decay into stable forms.

Physical Half-Life

The time required for $50\%$ of a radioactive isotope to naturally decay into a stable form.

Biological Half-Life

The time required for a living organism to eliminate half of a substance from the body through metabolic processes.

Octet Rule

The chemical principle stating that atoms tend to lose, gain, or share electrons to obtain a full outer shell containing eight valence electrons.

Valence Shell

The outermost electron shell of an atom, which determines its chemical reactivity and stability.

Cation

An atom or group of atoms carrying a net positive charge due to the loss of one or more electrons.

Anion

An atom or group of atoms carrying a net negative charge due to the gain of one or more electrons.

Polyatomic Ion

An ion composed of two or more covalently bonded atoms carrying a net overall electrical charge.

Ionic Bond

A chemical bond formed by electrostatic attraction between oppositely charged cations and anions following an electron transfer.

Covalent Bond

A chemical bond formed when two or more atoms share electrons to achieve stability.

Molecular Formula

A chemical representation showing the exact number and types of atoms present in a molecule.

Structural Formula

A chemical representation indicating the arrangement and spatial bonding structure of atoms within a molecule.

Isomers

Molecules that share the same molecular formula but possess different structural arrangements in space.

Electronegativity

The relative attraction that an atom exerts on shared electrons within a covalent bond.

Nonpolar Covalent Bond

A covalent bond formed between two atoms with equal electronegativities, resulting in equal electron sharing.

Polar Covalent Bond

A covalent bond formed between atoms with differing electronegativities, causing unequal electron sharing and partial charges.

Amphipathic Molecule

A large molecule possessing both polar (hydrophilic) and nonpolar (hydrophobic) structural regions.

Hydrogen Bond

A weak attraction between a partially positive hydrogen atom in a polar molecule and a partially negative atom in another polar molecule.

Hydrophobic Exclusion

The process by which cohesive polar water molecules push out nonpolar molecules, driving them to aggregate.

Cohesion

The attraction occurring between adjacent water molecules due to hydrogen bonding.

Adhesion

The attraction between water molecules and a different non-water substance.

Surface Tension

The inward pulling cohesive force existing at the surface of a body of water.

Specific Heat

The amount of thermal energy required to raise the temperature of $1\,\text{gram}$ of a substance by $1^\circ\text{C}$.

Heat of Vaporization

The amount of energy required to transform $1\,\text{gram}$ of a liquid substance into a gas.

Hydrophilic

Refers to polar molecules and charged ions that readily dissolve in water ('water-loving').

Hydrophobic

Refers to nonpolar molecules that do not dissolve in water ('water-fearing').

Acid

A substance that dissociates in water to yield hydrogen ions ($\text{H}^+$) and an anion, acting as a proton donor.

Base

A substance that binds free hydrogen ions ($\text{H}^+$) when added to a solution, acting as a proton acceptor.

pH

A logarithmic measure of the concentration of free hydrogen ions ($\text{H}^+$) in a solution.

Buffer

A substance or mixture that helps prevent changes in $\text{pH}$ by absorbing or releasing hydrogen ions ($\text{H}^+$).

Suspension

A mixture containing particles larger than $1\,\mu\text{m}$ that scatter light and settle out when not in motion.

Colloid

A mixture containing intermediate-sized particles that scatter light but remain dispersed when at rest.

Solution

A homogeneous mixture containing solute particles smaller than $1\,\text{nanometer}$ that dissolve fully and do not scatter light or settle.

Emulsion

A distinct category of colloid created by agitating a combination of a polar liquid and a nonpolar liquid.

Molarity

A concentration unit measured as moles of solute per liter of solution ($\text{mol/L}$).

Molality

A concentration unit measured as moles of solute per kilogram of solvent ($\text{mol/kg}$).

Mole

A quantity of a substance containing $6.022 \times 10^{23}$ particles, equivalent in mass to its atomic or molecular mass in grams.

Dehydration Synthesis

A condensation reaction that forms biomolecules by removing an $-\text{H}$ from one subunit and an $-\text{OH}$ from another, creating water.

Hydrolysis

A chemical breakdown reaction that uses water to split biomolecules, adding an $-\text{H}$ to one subunit and an $-\text{OH}$ to the other.

Triglyceride

A lipid used for long-term energy storage composed of one glycerol molecule attached to three fatty acids.

Lipogenesis

The metabolic pathway that creates triglycerides from excess nutrients via dehydration synthesis.

Lipolysis

The metabolic pathway that breaks down triglycerides into glycerol and fatty acids via hydrolysis.

Glycogenesis

The process of storing excess glucose by linking glucose monomers together into glycogen in liver and muscle cells.

Glycogenolysis

The hydrolysis of stored glycogen into glucose units by the liver when body energy levels drop.

Nucleotide

The monomer building block of nucleic acids, consisting of a pentose sugar, a phosphate group, and a nitrogenous base.

Pyrimidine

A single-ring nitrogenous base category comprising cytosine, uracil, and thymine.

Purine

A double-ring nitrogenous base category comprising adenine and guanine.

Adenosine Triphosphate (ATP)

A nucleotide composed of adenine, ribose sugar, and three phosphate groups that serves as the cell's main energy molecule.

Primary Structure

The linear sequence of amino acids joined together by peptide bonds in a protein.

Secondary Structure

Repeating structural patterns within a protein, such as alpha helices or beta sheets, formed by hydrogen bonds.

Tertiary Structure

The final three-dimensional folded shape of a single polypeptide chain, classified as globular or fibrous.

Quaternary Structure

The level of protein structure present in functional molecules composed of two or more distinct polypeptide strands.

Denaturation

A structural change in a protein's conformation that disrupts its biological function, caused by heat or extreme $\text{pH}$.