BioGT Ch2: Elements, Atoms, and Compounds

Matter

Anything that occupies space and has mass.

Element

A substance that cannot be broken down into other substances by ordinary chemical means.

Compound

A substance made of two or more elements in a fixed ratio.

Trace elements

Elements that are necessary for survival, but are scarce in the human body.

Atom

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

Proton

A subatomic particle with a single positive electric charge, found in the nucleus.

Neutron

A subatomic particle with no charge, found in the nucleus.

Electron

A subatomic particle with a single negative charge, moves around the nucleus.

Nucleus

The central part of an atom, made of tightly packed neutrons and protons.

Isotope

Different forms of an element that have the same number of protons but different numbers of neutrons.

Radioactive isotopes

Isotopes that have spontaneously decaying nuclei and can be a risk to living organisms.

Chemical bonds

Interactions between atoms that involve the sharing or transfer of electrons.

Valence shell

The outermost electron shell of an atom.

Covalent bond

A bond formed when two atoms share a pair of electrons.

Nonpolar bond

A covalent bond between atoms with equally shared electrons.

Polar bond

A covalent bond between atoms with unequally shared electrons.

Ionic bond

An attraction between ions of opposite charge.

Ion

An atom or molecule with a positive or negative electrical charge resulting from a gain or loss of electrons.

Hydrogen bond

A weak bond formed when the partially positive side of a water molecule interacts with nearby atoms that have a negative charge.

Chemical reactions

Processes that rearrange matter by making and breaking chemical bonds.