Chemical Basis of Life I: Atoms, Molecules and Water

Comprehensive vocabulary flashcards covering matter, energy, subatomic structure, chemical bonding, and types of chemical reactions from Chapter 2.

Matter

Anything that occupies space and has mass, existing in solid, liquid, or gaseous states.

Physical Change

A change that alters a substance without altering its basic nature or chemical composition, such as changes in the state of matter.

Chemical Change

A change that alters the chemical composition of a substance.

Energy

The ability to do work, possessing no mass and occupying no space.

Kinetic Energy

Energy that is actively doing work.

Potential Energy

Energy that is inactive or stored.

Chemical Energy

A form of energy stored in the chemical bonds of substances.

Electrical Energy

Energy resulting from the movement of charged particles.

Mechanical Energy

Energy directly involved in moving matter.

Radiant Energy

Energy of the electromagnetic spectrum that travels in waves.

Major Elements of Life

The four elements that make up $96\%$ of living organisms: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

Atom

The fundamental building block of an element, differing in structure from atoms of other elements.

Proton

A subatomic particle located in the nucleus with a mass of $1\,\text{amu}$ and a positive ($+$) electrical charge.

Neutron

An uncharged ($0$) subatomic particle located in the nucleus with a mass of $1\,\text{amu}$.

Electron

A negatively charged ($-$) subatomic particle orbiting the nucleus with a negligible mass of $1/2000\,\text{amu}$ (assumed to be $0\,\text{amu}$).

Planetary Model

An atomic model portraying the atom as a miniature solar system with protons and neutrons in the nucleus and electrons in fixed circular orbits.

Orbital Model

An atomic model depicting electrons within probabilistic regions called orbitals or electron clouds around the nucleus.

Atomic Number

A number equal to the number of protons contained in an atom, which is unique to each element and indirectly gives the electron count in a neutral atom.

Atomic Mass Number

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

Atomic Weight

A value approximately equal to the mass number of an element's most abundant isotope, calculated as a weighted average across all isotopes.

Isotopes

Atoms of the same element that have the same number of protons and electrons but differ in their number of neutrons, resulting in different atomic masses.

Radioactivity

The process of spontaneous atomic decay exhibited by heavy, unstable isotopes as they decompose into more stable isotopes.

Molecule

Any chemical unit consisting of two or more atoms bound together.

Compound

A specific type of molecule that contains atoms of at least two different elements chemically combined.

Chemical Bond

An energy relationship involving interactions between the electrons of reacting atoms.

Valence Shell

The outermost electron shell of an atom whose electrons participate in chemical bonding and dictate chemical reactivity.

Rule of Eights

The principle that atoms are chemically stable and inert when their outermost shell contains 8 electrons, with the exception of shell 1, which holds a maximum of 2 electrons.

Ionic Bond

A chemical bond formed when electrons are completely transferred from one atom to another, producing charged ions that attract.

Anion

A negatively charged ion produced when an atom gains one or more electrons.

Cation

A positively charged ion produced when an atom loses one or more electrons.

Covalent Bond

A chemical bond formed when atoms share pairs of electrons to achieve valence shell stability.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between the atoms, resulting in an electrically neutral molecule.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally between atoms, producing a molecule with positive and negative poles.

Hydrogen Bond

An extremely weak bond formed when a hydrogen atom is attracted to the negative portion (such as oxygen or nitrogen) of another polar molecule.

Van der Waals Forces

Weak, short-range, distance-dependent electrostatic attractions between atoms and molecules that result from temporary fluctuations in electron distribution.

Synthesis Reaction

A chemical reaction ($A + B \rightarrow AB$) in which atoms or molecules combine to form a larger, more complex molecule while absorbing energy.

Decomposition Reaction

A chemical reaction ($AB \rightarrow A + B$) in which bonds are broken in larger molecules to produce smaller molecules, releasing chemical energy.

Exchange Reaction

A chemical reaction ($AB + C \rightarrow AC + B$) involving both synthesis and decomposition, where parts of the reactant molecules switch to form new molecules.

Dehydration Synthesis

A reaction in which monomers or building blocks are covalently linked to form polymers through the removal of water molecules.

Hydrolysis

A reaction in which polymers are broken down into monomers through the addition of water molecules, adding $-\text{OH}$ to one monomer and $-\text{H}$ to the other.

Reversible Reaction

A chemical reaction that can proceed in either direction, designated by double arrows where differing lengths indicate the dominant direction or faster rate.

Catalyst

A substance that decreases the activation energy required for a chemical reaction by holding reactants in the proper positions to interact, thereby increasing reaction rate.