Chapter 2- Chemical level of organization

Anything that occupies space and has mass -The substance of the universe -from a grain of sand to a star

A pure substance that is distinguished from all other matter by the fact that it cannot be created or broken down by ordinary chemical means -All matter in the natural world is composed of one or more of the 92 fundamental substances called elements

A substance composed of two or more elements joined by chemical bonds -Elements combine to form compounds ex: the compound glucose is composed of carbon, hydrogen, and oxygen

The smallest quantity of an element that retains the unique properties of that element ex: An atom of hydrogen is a unit of hydrogen

Three subatomic particles: proton neutron electron

The number of positively- charged protons and non-charged (neutral) neutrons

The number of negatively-charged electrons that “spin” around the nucleus at close to the speed of light

1/2000th

The number of protons in the nucleus of the atom, identifies the element

The sum of the number of protons and neutrons in the nucleus

A chart identifying the 92 elements found in nature, as well as several larger, unstable elements discovered experimentally

One of the different forms of an element, distinguished from one another by different number of neutrons

A layer of electrons that encircle the nucleus at a distinct energy level

An atom’s outermost electron shell -If the v shell is full, the atom is stable; its electrons are unlikely to be pulled away from the nucleus by the electrical charge of other atoms -If the v shell is not full the atom is reactive; it will tend to react with other atoms in ways that make the v shell full ex: hydrogen with its one electron only half-filling its v shell. This single electron is likely to be drawn into relatiosnhips w the atoms of other elemtns, so that hydrogen’s single v shell can be stabilized

Atoms link by forming a chemical bond A bond is a weak or strong electrical attraction that holds atoms in the same vicinity

An atom that has an electrical charge - whether positive or negative

A positively charged ion

A negatively charged ion

An ongoing, close association betweens ions of opposite charge -Formed by the attraction between a cation’s positive chargr and an anion’s negative charge

Molecules formed by a CB share electrons in a mutually stabilizing relationship ex: The atoms do not lose or gain electrons permanently, instead the electrons move back and forth between the elements

Because of the close sharing of pairs of electrons (one electron from each of two atoms)

Covalently bonded molecules that are electrically balanced. No region of the molecule is either more positive or more negative than any other

Molecules that do not have any electrical charges or partial charges -Made of atoms that have a similar value of electronegativity (the tendency of an atom to attract electrons)

Exists when atoms with different electronegativities share electrons in a covalent bond