Word | Definition |
John Newlands | 1865 the English chemist arranged the known elements according to their properties and in order of increasing atomic mass. Made the Periodic Table. Noticed that they repeat every eight elements, called this pattern the Law of Octaves. |
Dmitri Mendeleev | 1869, Russian chemist used Newlands’s observations and information to produce the first orderly arrangement of the 63 known at the time. Wrote symbol for each element along with the physical and chemical prosperities, relative mass of the element. He plac |
Henry Moseley | After 40 years he discovered a different physical basis for the arrangement of elements. Studied the lines in the X-ray spectra of 38 different elements. Found that the wavelengths of the lines decreased in a regular manner as atomic mass increased. When |
Periodic Law | The law that states that the repeating physical and chemical properties of elements change periodically with their atomic number. |
Valence Electron | an electron that is found in the outermost shell of and atom and that determines the atom’s chemical properties. |
Group | a vertical column of elements in the periodic table; elements in a group share chemical properties. |
Period | a hori9zontal row of elements in the periodic table. |
Main Group elements | and element in the s-block or p-block of periodic table. Groups 1,2 and 13-18. |
Alkali metal | one of the elements of Group 1 of the periodic table. They react with water to make alkaline solutions. Because they have a single valence electron they are very reactive. In losing one valence electron they achieve a stable electron configuration. They a |
Alkaline | earth metals – one of the elements of Group 2 of the Periodic table. They are highly reactive, usually found as compound than as pure elements. They have 2 valence electrons and must lose both to get to a stable electron configuration. This takes more ene |
Halogens | Found in group 17. They are the most reactive of the nonmetal elements because of their electron configuration. They often gain one electron to have the needed eight valence electrons to fill the electron configuration. They start out with 7 valence elect |
Noble gases | an unreactive element of group 18 of the periodic table. They have eight electrons (or a full set of valence electrons) in its outer level. (except for helium which has two electrons) They have a low chemical reactivity, and are very stable. They were onc |
Transition metals | one of the metals that can use the inner shell before using the outer shell to bond. Found in groups 3-12 and sometimes called the d-block elements. They do not have identical outer shell electron configurations. They can lose different numbers of valence |
Alloy | a solid or liquid mixture of two or more metals. |
Bond Radius | half the distance form center to center of two like atoms that are bonded together. |
Electronegativity | a measure of the ability of an atom in a chemical compound to attract electrons. Chemical bonding that comes from shared electrons. It decreases as you move down a group. It also increases as you move across the table. |
Octet rule | a concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty valence shells or full valence shells of eight electrons. |
Ion | an atom, radical or molecule that has gained or lost one or more electrons and has a negative or positive charge. |
Cation | an ion that has a positive charge |
Anion | an ion that has a negative charge. |
Lattice energy | the energy associated with construction a crystal lattice relative to the energy of constituent atoms separated by infinite distances. |
Crystal lattice | the regular pattern in which a crystal is arranged. |
Polyatomic ion | an ion made of two or more atoms. |
Covalent bond | a bond formed when atoms share one or more pairs of electrons. |
Molecular orbital | the region of high probability that is occupied by an individual electron as it travels with a wavelike motion in the three-dimensional space around one of two or more associated nuclei. |
Nonpolar covalent bond | a covalent bond in which the bonding electrons are equally attracted to both bonded atoms. |
Polar covalent bond | a covalent bond in which a shared pair of electron is held more closely by one of the atoms. |
Dipole | a molecule or part of a molecule that contains both positively and negatively charged regions. Use the delta sign to help in the writing of formula. |
Lewis Structure | a structural formula in which electrons are represented by dots, dot pairs or dashes between two atomic symbols represent pairs in covalent bonds. |