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What did Cannizarro do? made a convincing method for accurately measuring the relative atomic masses What did Mendeleev do? arranged in order of increasing atomic mass What is the periodic law? the physical and chemical properties of the elements are periodic functions of their atomic numbers What is the periodic table? is an arragement of the elements in order of their atomic numbers so that elemetns with similar properties fall in the same column or group Define Lanthanides are the 14 elements with atomic numbers from 58 to 71 Define Actinides are the 14 elements with atomic numbers 90 to 103 By atomic numbers In the modern periodic tabke, how are elements arranged Alkali Metals elements that often have a silvery apperance and are soft to cut. not found in nature and usually stored in kerosene. highly reactive to most non metals and water. Alkaline metals elements that are harder, denser, and stronger than group 1 elements and less active. also have higher melting points and arent found in nature Transition elements d block elements with typical metallic properties. good conductors of electricity and less reactive. Main group elements the p block elements together with the s block elements Halogens group 17 elements that react vigorously with most metals to form salts Metalloids mostly brittle solids that have electrical conductivity Atomic Radius defined as one-half the distance between the nuclei of identical atoms that are bonded together What is the trend for atomic radius across a period is smaller and increase down a group Ion is an aton or group of bonded atoms that has a positive or negative charge Ionization any process that results in formation of an ion Ionization Energy (IE1) the energy required to remove one electron from a neutral atom of an element What is the trend for IE increase across a period and decrease down a group Second ionization energy the energies for removal of addittional electrons from an atom Electron Affinity the energy change that occus when an electron is acquired by a neutral atom Cation a positive ion Anion a negative ion Valence electrons the electrons available to be lost, gained, or shared in the formation of chemical compounds