Chemistry Basics: Atoms, Bonds, and Molecules

Vocabulary flashcards covering key chemistry concepts from the lecture notes.

Element

The simplest form of matter with unique chemical properties.

Periodic table

A chart listing elements by atomic number and symbol; used to organize and identify elements.

Atomic number

Number of protons in an atom's nucleus; identifies the element.

Proton

Positively charged subatomic particle in the nucleus; mass ≈ 1 atomic mass unit (amu).

Neutron

Electrically neutral subatomic particle in the nucleus; mass ≈ 1 amu.

Electron

Negatively charged subatomic particle in electron shells; involved in bonding; very small mass.

Atomic mass

Sum of the protons and neutrons in the nucleus; approximate mass of the atom.

Nucleus

Center of the atom containing protons and neutrons.

Valence electrons

Electrons in the outermost shell that determine bonding behavior.

Electron shell

Energy levels surrounding the nucleus that hold electrons; shells fill in order.

Isotopes

Variants of an element with different numbers of neutrons; chemically similar but with different atomic mass.

Radioisotopes

Unstable isotopes that decay and emit radiation.

Radioactivity

Emission of radiation as unstable nuclei decay.

Ion

A charged particle formed by gaining or losing electrons; carries a net charge.

Anion

Negatively charged ion formed by gaining electrons.

Cation

Positively charged ion formed by losing electrons.

Salt

An ionic compound made of cations and anions; typically dissociates in water.

Electrolyte

Substances that ionize in water to form conductive solutions.

Free radical

Highly reactive species with unpaired electrons that can damage molecules.

Superoxide anion

Reactive oxygen species with the formula O2−; can cause cellular damage.

Antioxidant

Substances that neutralize free radicals to prevent damage.

Superoxide dismutase

Enzyme that neutralizes superoxide radicals.

Molecular formula

Notation showing the types and numbers of atoms in a molecule.

Isomer

Molecules with the same molecular formula but different structures.

Molecular weight

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

Covalent bond

Bond formed by sharing electrons between atoms.

Ionic bond

Bond formed by transfer of electrons, creating oppositely charged ions.

Nonpolar covalent bond

Covalent bond where electrons are shared equally.

Polar covalent bond

Covalent bond where electrons are shared unequally, creating partial charges.

Hydrogen bond

Weak attraction between a hydrogen atom and an electronegative atom in another molecule; often occurs between water molecules.

Van der Waals forces

Very weak intermolecular attractions due to transient electron density variations.

Water (H2O)

Molecule with two hydrogens and one oxygen held together by covalent bonds; forms hydrogen bonds between molecules.

Ionization

Process of gaining or losing electrons to form ions.

Biological electrolytes

Electrolytes balance is critical for nerve and muscle function and overall homeostasis.

Half-life

Time required for half of a radioactive substance to decay.

Biological half-life

Time required for the body to eliminate half of a radioisotope.

Madame Curie

Pioneer who coined the term radioactivity and discovered polonium and radium; first female Nobel Prize laureate.

Radioisotope use in medicine

Radioisotopes are used for diagnostic testing (e.g., thyroid function) in medical contexts.

DNA mutations

Radiation-induced damage to DNA can lead to mutations and potentially cancer.