1 Atoms, Isotopes, Elements & the Periodic Table – Vocabulary Flashcards

A vocabulary-focused set of flashcards covering core terms from the lecture notes on matter, atoms, isotopes, bonds, water chemistry, carbon, and basic biochemistry.

Matter

Anything that occupies space and has mass; all living and nonliving substances.

Element

Pure substance made of only one type of atom; 118 known elements, with a few dominating living systems.

Atom

The basic unit of an element, consisting of a nucleus (protons and neutrons) and electrons in surrounding shells.

Nucleus

The center of an atom that contains protons and neutrons.

Proton

A positively charged subatomic particle in the nucleus (mass ≈ 1 amu).

Neutron

An electrically neutral subatomic particle in the nucleus (mass ≈ 1 amu).

Electron

A negatively charged subatomic particle surrounding the nucleus; very small mass.

Atomic Number

The number of protons in an atom, which defines the element.

Mass Number

The total number of protons and neutrons in the atom’s nucleus.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons.

Carbon-12

An isotope of carbon with 6 neutrons.

Carbon-13

An isotope of carbon with 7 neutrons.

Radioisotope

An unstable isotope that decays over time, releasing energy and particles.

Half-life

The time required for half of a radioactive substance to decay.

Electron Configuration

The arrangement of electrons in energy levels around the nucleus; outer electrons determine reactivity.

Periodic Table

Organization of elements by electron configuration; elements with similar properties are grouped together.

Group (Periodic Table)

A vertical column in the periodic table; elements in a group share properties.

Ion

An atom that has gained or lost electrons, resulting in a net charge.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Ionic Bond

An electrostatic attraction between oppositely charged ions (e.g., Na+ and Cl−).

Covalent Bond

A bond formed by sharing electrons between atoms.

Polar Covalent Bond

A covalent bond with unequal sharing of electrons, creating partial charges.

Nonpolar Covalent Bond

A covalent bond with equal sharing of electrons and no partial charges.

Water Polarity

Water molecules are polar, with partial positive charges on hydrogens and a partial negative charge on oxygen.

Hydrogen Bond

A weak attraction between a hydrogen atom and a electronegative atom in another molecule.

Cohesion

Attraction between water molecules, contributing to surface tension.

Adhesion

Water’s attraction to other substances, enabling capillary action.

Hydrophilic

Substances that are water-loving and dissolve in water due to polarity.

Hydrophobic

Substances that are water-fearing and do not mix well with water (nonpolar).

Specific Heat

Water’s high capacity to absorb heat without a large temperature change.

Density (Ice vs. Water)

Water is densest at 4°C; ice is less dense than liquid water and floats.

Buffer

A substance that resists pH changes by neutralizing added acids or bases (e.g., bicarbonate system in blood).

pH

A scale that measures how acidic or basic a solution is (0–14).

Hydrolysis

A reaction that uses water to break chemical bonds.

Dehydration Synthesis

A reaction that joins monomers by releasing a molecule of water.

Carbon Skeleton

The framework of carbon chains/structures forming sugars, fatty acids, amino acids, and nucleotides.

Macromolecule

Large biological polymers such as proteins, carbohydrates, lipids, and nucleic acids.

Monomer

A small molecule that can join with others to form a polymer.

Polymer

A long chain of repeating monomer units.

Valence/Tetravalence

Valence is the number of electrons available for bonding; carbon has four, making it tetravalent.

Hydrocarbons

Compounds consisting only of carbon and hydrogen, which can be linear, branched, or ring-shaped.

Isomer

Molecules with the same formula but different structures and properties.

Functional Group

A specific group of atoms that imparts characteristic reactivity/polarity (e.g., –OH, –COOH).

Hydroxyl Group

–OH; polar and capable of hydrogen bonding; common in alcohols and sugars.

Carboxyl Group

–COOH; acidic group found in amino and fatty acids.

Amino Group

–NH2; basic group found in amino acids.

Phosphate Group

–PO4; essential in energy transfer (ATP) and nucleotides.

Chirality (R/S Enantiomers)

Molecules can exist as non-superimposable mirror images (R and S forms), as seen in thalidomide.

Potassium-41 (K-41)

An isotope of potassium with one more neutron than the most common isotope; isotopes differ in neutrons, not protons.