Chapter 2: The Chemical Context of Life - Vocabulary

Vocabulary flashcards generated from Chapter 2 lecture notes covering basic chemical principles, subatomic particles, isotopes, electron behavior, and chemical bonding types.

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 individual elements.

Trace Elements

Elements required by an organism in minute quantities, accounting for less than $0.01\text{\%}$ of human body weight.

Atom

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

Neutrons

Subatomic particles located in the atomic nucleus that have no electrical charge and a mass close to $1\text{ Dalton}$.

Protons

Subatomic particles located in the atomic nucleus that carry a positive ($+\text{ charge}$) and have a mass close to $1\text{ Dalton}$.

Electrons

Subatomic particles carrying a negative ($-\text{ charge}$) that form a cloud around the atomic nucleus.

Atomic Number

The number of protons in the nucleus of an atom, which also indicates the number of electrons in an electrically neutral atom.

Mass Number

The total sum of protons plus neutrons in the nucleus of an atom.

Atomic Mass

An approximation of the total mass of an atom, derived from its mass number.

Isotopes

Two atoms of the same element that differ in their number of neutrons, resulting in different mass numbers.

Radioactive Isotope

An unstable isotope whose nucleus spontaneously decays, giving off particles and energy.

Energy

The capacity to cause change, such as by doing work.

Potential Energy

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

Electron Shells

States of potential energy for electrons, each with a characteristic average distance from the nucleus and energy level.

Valence Electrons

Electrons located in the outermost shell of an atom that primarily determine its chemical behavior.

Valence Shell

The outermost electron shell of an atom; when full, the atom is unreactive.

Orbital

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

Chemical Bonds

Attractions that hold atoms close together, formed through the sharing or transfer of valence electrons.

Covalent Bond

A chemical bond formed by the sharing of a pair of valence electrons by two atoms.

Molecule

Two or more atoms held together by covalent bonds.

Single Bond

A covalent bond involving the sharing of one pair of valence electrons.

Double Bond

A covalent bond involving the sharing of two pairs of valence electrons.

Valence

An atom's bonding capacity, which usually equals the number of unpaired electrons in its valence shell.

Electronegativity

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

Nonpolar Covalent Bond

A type of covalent bond in which electrons are shared equally between two atoms.

Polar Covalent Bond

A covalent bond between atoms that differ in electronegativity, causing unequal sharing of electrons.

Ion

A charged atom or molecule.

Anion

A negatively charged ion.

Cation

A positively charged ion.

Ionic Bond

A chemical bond resulting from the attraction between oppositely charged ions (anions and cations).

Ionic Compounds

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

Hydrogen Bond

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

Van der Waals Interactions

Weak, transient attractions between molecules or atoms that occur due to fleeting charge differences when they are very close together.