Chemical Basis of Life I: Atoms, Molecules and Water

Vocabulary flashcards covering atomic structure, subatomic particles, isotopes, chemical bonding types, and patterns of chemical reactions.

Kinetic energy

Energy that is actively doing work and able to perform downstream tasks.

Potential energy

Energy that is inactive or stored, which has the capacity to be converted into kinetic energy.

Chemical energy

A form of energy that is stored within the chemical bonds of substances.

Electrical energy

A form of energy that results from the movement of charged particles.

Mechanical energy

Energy directly involved in moving matter.

Radiant energy

Energy that travels in waves and constitutes the energy of the electromagnetic spectrum.

Anabolism

A metabolic pathway in which simpler substances are combined using energy to form complex molecules.

Catabolism

A metabolic pathway in which complex molecules are broken down into simpler molecules, releasing energy.

Element

A fundamental unit of matter; approximately $96\%$ of living organisms are composed of carbon, hydrogen, oxygen, and nitrogen.

Atom

The fundamental building block of an element, where atoms of different elements differ from one another.

Atomic symbol

A chemical shorthand abbreviation used to designate each specific element.

Proton

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

Neutron

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

Electron

A subatomic particle orbiting the atomic nucleus with a mass of $1/2000\,\text{amu}$ and a negative ($-$) charge, which dictates whether an atom is chemically reactive.

Planetary model

An atomic model that depicts electrons in orbit around the central nucleus in fixed circular paths, analogous to planets circling the sun.

Orbital model

A modern atomic model depicting regions around the nucleus as a cloud or haze of negative charge representing the probable locations of electrons.

Atomic number

A value equal to the number of protons contained in an atom's nucleus, which is unique to each element and indirectly identifies the number of electrons 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 of each isotope's mass multiplied by its fractional abundance.

Isotopes

Structural variants of an element that contain the same number of protons and electrons but differ in their number of neutrons, yielding different atomic masses.

Radioactivity

The process of spontaneous atomic decay wherein heavy, unstable isotopes decompose into more stable isotopes.

Molecule

Any chemical structure composed of two or more atoms bound together, such as $H_2$.

Compound

A specific type of molecule composed of atoms of at least two different elements bonded together, such as methane ($CH_4$).

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 the atom's chemical behavior.

Chemically inert elements

Elements whose outermost valence shells are completely filled (holding $2$ electrons in shell $1$, or $8$ electrons in outer shells), making them stable and unreactive.

Rule of eights

The chemical principle stating that atoms achieve stability when their valence shell contains $8$ electrons, with the exception of shell $1$, which can hold a maximum of $2$ electrons.

Chemically reactive elements

Elements with incomplete outermost valence shells that tend to gain, lose, or share electrons with other atoms to achieve stability.

Ionic bond

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

Anion

A negatively charged ion that results from the gain of one or more electrons.

Cation

A positively charged ion that results from the loss of one or more electrons.

Covalent bond

A chemical bond in which atoms achieve electronic stability by sharing pairs of electrons.

Single covalent bond

A covalent bond formed when two reacting atoms share one pair of electrons, represented as a single line (e.g., $H-H$).

Double covalent bond

A covalent bond formed when two reacting atoms share two pairs of electrons, represented as a double line (e.g., $O=O$).

Nonpolar covalent bond

A covalent bond in which shared electrons are distributed equally between the bonded atoms, making the resulting molecule electrically neutral (e.g., $CO_2$).

Polar covalent bond

A covalent bond in which electrons are shared unequally, producing a molecule with distinct positive and negative poles (e.g., $H_2O$).

Hydrogen bond

An extremely weak chemical 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 or molecules that arise from temporary fluctuations in electron distribution.

Synthesis reaction

A chemical reaction ($A + B \rightarrow AB$) where smaller particles are bonded together to form larger, more complex molecules, absorbing energy for bond formation.

Decomposition reaction

A chemical reaction ($AB \rightarrow A + B$) in which bonds within larger molecules are broken down into smaller, less complex molecules, releasing chemical energy.

Exchange reaction

A chemical reaction ($AB + C \rightarrow AC + B$) involving both synthesis and decomposition, where bonds are made and broken to switch molecular parts and generate different molecules.

Dehydration synthesis

A reaction where monomers are joined together to form polymers by removing an $-OH$ group from one monomer and an $-H$ from the other to release water ($H_2O$).

Hydrolysis

A reaction in which polymers are broken down into monomers through the addition of a water molecule, adding an $-OH$ group to one monomer and an $-H$ to the other.

Catalyst

A substance that speeds up a chemical reaction by holding reactants in proper orientations, thereby decreasing the activation energy needed for them to interact.