The Chemical Context of Life

Vocabulary flashcards covering chemical elements, subatomic particles, chemical bonds, molecular structures, and chemical reactions based on Chapter 2 lecture notes.

Biology

The study of life.

Matter

Anything that takes up space and has mass.

Element

A substance that cannot be broken down to other substances by chemical reactions.

Compound

A substance consisting of two or more elements in a fixed ratio, possessing characteristics different from those of its elements.

Essential elements

Elements required for life, which make up about $20\%$ to $25\%$ of the $92$ natural elements.

Trace elements

Elements required by an organism in only minute quantities.

Serpentine

A type of soil/environment containing toxic elements to which specific plant communities can become adapted.

Atom

The smallest unit of matter that still retains the properties of an element.

Neutrons

Subatomic particles located in the atomic nucleus with no electrical charge.

Protons

Subatomic particles located in the atomic nucleus carrying a positive charge.

Electrons

Subatomic particles carrying a negative charge that form a cloud around the atomic nucleus.

Atomic nucleus

The dense central core of an atom formed by protons and neutrons.

Daltons

The unit of measurement used for neutron mass and proton mass.

Atomic number

The number of protons contained in the nucleus of an element's atom.

Mass number

The sum of protons plus neutrons in an atom's nucleus.

Atomic mass

An atom's total mass, which can be approximated by its mass number.

Isotopes

Two atoms of an element that have the same number of protons but differ in their number of neutrons.

Radioactive isotopes

Isotopes that decay spontaneously, giving off particles and energy.

Half-life

The fixed rate at which a parent isotope decays into its daughter isotope.

Radiometric dating

A method in which scientists measure the ratio of different isotopes and calculate how many half-lives have passed since a fossil or rock was formed.

Energy

The capacity to cause change.

Potential energy

The energy that matter possesses because of its location or structure.

Energy level (Electron shell)

An electron's state of potential energy.

Valence electrons

Electrons occupying the outermost shell, or valence shell, of an atom.

Valence shell

The outermost electron shell of an atom.

Orbital

The three-dimensional space where an electron is found $90\%$ of the time.

Chemical bonds

Attractions that hold atoms close together, resulting from the sharing or transferring of valence electrons.

Covalent bond

The sharing of a pair of valence electrons by two atoms.

Molecule

Two or more atoms held together by covalent bonds.

Single covalent bond

The sharing of one pair of valence electrons by two atoms.

Double covalent bond

The sharing of two pairs of valence electrons by two atoms.

Structural formula

A notation used to represent atoms and bonding, such as $\text{H-H}$.

Molecular formula

An abbreviated formula representing the composition of a molecule, such as $H_2$.

Valence

An atom's bonding capacity.

Electronegativity

An atom's attraction for the electrons in a covalent bond.

Nonpolar covalent bond

A type of covalent bond in which the atoms share electrons equally.

Polar covalent bond

A type of covalent bond where one atom is more electronegative, leading to unequal electron sharing and partial charges.

Ion

A charged atom or molecule.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Ionic bond

A chemical attraction formed between an anion and a cation.

Ionic compounds (Salts)

Compounds formed by ionic bonds, often found as crystals in nature.

Hydrogen bond

A weak attraction formed when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom.

Van der Waals interactions

Weak attractions between molecules that are close together resulting from transient, uneven electron distributions.

Reactants

The starting molecules of a chemical reaction.

Products

The final molecules produced by a chemical reaction.

Photosynthesis

An essential chemical reaction powered by sunlight converting carbon dioxide and water into glucose and oxygen ($6\,CO_2 + 6\,H_2O \rightarrow C_6H_{12}O_6 + 6\,O_2$).

Chemical equilibrium

The state reached when the forward and reverse chemical reactions occur at the same rate, keeping the relative concentrations of reactants and products unchanged.