Essential Biology w/ Physiology: Ch. 2 - Atoms

Radioactive Isotope

One in which the nucleus decays spontaneously, shedding particles and energy. *Radiation from decaying isotopes can damage cellular molecules and thus can pose serious health risks.

O, C, H, and N elements

Most abundant elements in living matter.

Proton

Subatomic particle with a single unit of positive electrical chart (+). They DETERMINE ElEMENT.

Atomic Number

The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of an atom. It is identical to the charge number of the nucleus. The atomic number uniquely identifies a chemical element.

Dalton

The mass of a proton and the mass of a neutron are almost identical and are expressed in a unit of measurement called the dalton. *Protons and Neutrons ea. have masses close to 1 dalton.

Atom

The smallest unit of matter that still retains the properties of an element. *Composed of subatomic particles, of which 3 are most important: Proton; Electron; Neutron.

Mass Number

The sum of the number of protons and neutrons.

Isotope

Nuclei containing the same number of protons but different numbers of neutrons. *Most elements can exist in several isotopic forms. Ex. A common example of an isotope is deuterium, which differs from a normal hydrogen by the presence of an extra neutron in the nucleus.

Neutron

1 of 2 subatomic particle occupy's the nucleus. Electrically neutral (has no charge). They DETERMINE ISOTOPE.

Radon

1. A naturally occurring radioactive gas. 2. Can cause lung cancer. 3. May contaminate buildings where underlying rocks naturally contain the radioactive element uranium.

Atomic Mass

1. Is listed in the periodic table as the bottom number (under the element symbol) and is close to its mass number, but may differ slightly because if represents an average of all the naturally occurring forms of that element.

Electron

1. The negatively charged subatomic particles of an atom Electrons in atoms exist in spherical shells of various radii, representing energy levels. The larger the spherical shell, the higher the energy contained in the electron. Outer shell electrons determine chemical behavior. 2. Only electrons are involved in chemical reactions. 3. The number of electrons in an atom deter- mines the chemical properties of that atom. * Chemical reactions enable atoms to or share electrons. These interactions usually result in atoms staying close together, held by attractions called chemical bonds. *Only has abt. 1/2000 the mass of a Proton, so its mass is approximated as zero.

Molecule

A tightly bound group of atoms held together by interactions among their orbiting electrons.- interactions called chemical bonds. *Can only exist in certain well-defined energy states.

Nucleus

Atoms central core/nucleus. Consists of protons and neutrons.

Chemical Bonding and Molecules

Transfer of one or more electrons produces attractions between oppositely charged ions: Attraction between oppositely charged ions holds the ions in an ionic bond.