Exam 1 Review:  Chapter 2 - Properties of Atoms

matter - Any physical substance which occupies space, has mass, and can be perceived by one or more senses; composed of atoms of various chemical elements.

energy - The capacity for performing work.  Chemical energy is derived from the ability of atoms and molecules to participate in the making or breaking of chemical bonds.

potential energy - The stored energy of a body or system, i.e., energy which is not kinetic, i.e., energy due to configuration; examples of potential energy include energy stored in a bent spring, or a body suspended a given distance above the earth and acted on by gravity.

kinetic energy - The active energy of a body, i.e., the energy it has as a result of being in motion; i.e., energy which is not potential; examples of kinetic energy include moving bodies, heat transference, electric currents, etc.

chemical element - A substance composed of atoms having an identical number of protons in each nucleus and an equal number of electrons in its outer shells. Elements cannot be reduced to simpler substances by normal chemical means.  Each element has its own unique chemical properties.  Elements are organized in the Periodic Table by their atomic numbers.

atom - A unit of matter, the smallest unit of an element, having all the characteristics of that element and consisting of a dense, central, positively charged nucleus surrounded by a system of electrons. The entire structure characteristically remains undivided in chemical reactions except for limited removal, transfer, or exchange of certain electrons.

nucleus (atomic) - The dense central core of an atom which contains the protons and neutrons.

electron - A stable sub-atomic particle with a negative charge.  Electrons are located in orbitals or electron shells at some distance from the nucleus of their respective atoms.   A flow of electrical current consists of the movement of many electrons.  Atoms of a given element contain the same number of protons as electrons.

proton -  A stable sub-atomic particle with a positive charge.  Protons are located in the nucleus of their respective atoms along with neutrons.  Atoms of a given element contain the same number of protons as electrons.

neutron - A stable sub-atomic particle with a neutral charge.  Neutrons are located in the nucleus of their respective atoms along with protons.  Atoms of a given element contain a variable number of neutrons (isotopes), generally equal to or nearly the same as the number of protons or electrons.

atomic number - The number which identifies a particular element by giving the number of protons, e.g., carbon has 6 protons and the atomic number 6.

mass - The quantity of matter which a body contains, irrespective of its bulk or volume.  (A property of matter equal to the measure of an object's resistance to changes in either the speed or direction of its motion. The mass of an object is not dependent on gravity and therefore is different from but proportional to its weight.)  The amount of mass in a material is equivalent to the sum of all the subatomic particles (protons, neutrons, and electrons) in the material.

mass number - The number which identifies a particular isotope of any element by giving the sum of number of protons and neutrons, e.g., carbon 14 = ¹⁴C contains 6 protons and eight neutrons.

isotope - One of two or more atoms with the same atomic number but with different numbers of neutrons, e.g., carbon 12 = ¹²C and carbon 14 = ¹⁴C.

radioactive isotope - Certain isotopes are unstable and transform (decay) into different isotopes losing protons or neutrons and are termed radioactive.

electron shell = orbital - The wave function of an electron in an atom or molecule, indicating the electron's probable location at a distance from the atomic nucleus; the outer shell or orbital of a given element contains a characteristic number of electrons and the number of those electrons determines how this atom will bond with other atoms.

valence - The combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms; represented by positive or negative integers, e.g., 1+, 2+, 1-, etc.

List:

 1. three particles which combine to form the atom.

          (positively charged) protons and (uncharged) neutrons (in the nucleus) and (negatively charged) electrons (in orbitals around the nucleus)

Sketch and Label:

1. a carbon atom, indicating the number and location of the protons and electrons.