Science Ch 12

Spencer lee B Ch 12 vocabulary Atom: The smallest particle into which an element can be divided and still retain all of the properties of that element. Theory: A unifying explanation for a broad range of hypothesis and observations that have been supported by testing. Electrons: The negatively charge particles found in all atoms; electrons are involved in the formation of chemical bonds. Models: A representation of an object or system. Nucleus: The tiny, extremely dense, positively charged region in the center of an atom, made up protons and neutrons. Electron Clouds: The regions inside an atom where electrons are likely to be found. Protons: The positively charged particles of the nucleus: the number of protons in a nucleus is the atomic number, which determines the identity of an element. Atomic Mass Unit: The SI Unit used to express the masses of particles in atoms. Neutrons: The particles of the nucleus that have no charge. Atomic Number: The number of protons in the nucleus of a atom, the atomic number is the same for all atoms of an element. Isotopes: Atoms that have the same number of protons but have different numbers of neutrons. Mass Number: The sum of protons and neutrons in an atom. Atomic Mass: The weighted average of the masses of all the naturally occurring isotopes of an element.

Spencer Lee B Ch 13 vocabulary Periodic: Having a regular, repeating pattern. Periodic Law: A law that states that the chemical and physical properties of elements are the periodic functions of their atomic numbers. Period: A horizontal row of elements on the periodical table. Group: A column of elements on the periodic table. Alkali Metal: Elements in group 1 of he periodic table; they are the most reactive metals and their atoms have one electron in their outer level. Alkaline-earth metals: Elements n Group 2 of the periodic table; they are reactive metals but less reactive than alkali metals; their atoms have two electrons in their outer level. Halogens: the elements in Group 17 of the periodic table; they are very reactive nonmetals and their atoms have seven electrons in their outer level. Noble Gases: A Unreactive metal in Group 18 of the periodic table; their atoms have eight electrons in their outer level.