The Periodic LawHistory of the Periodic Table Chapter 5.1
Objectives Explain the roles of Mendeleev and Moseley in the development of the periodic table. Describe the modern periodic table. Explain how the periodic law can be used to predict the physical and chemical properties of elements Describe how the elements belonging to a group of the periodic table are interrelated in terms of atomic number.
Early History By 1860 – more than 60 elements had been discovered. September of 1860 – First international Congress of Chemists met Cannizzaro – convincing method for measuring relative atomic mass Became a standard for showing relationship between atomic mass and properties of elements Stanislao Cannizzaro
Mendeleev and Periodicity Russian Chemist – Dmitri Mendeleev First usable periodic table Arranged according to : 1. Properties 2. Atomic mass Interesting facts: 1. Some Atomic masses were out of place 2. Empty spaces for elements not yet discovered. Later they were and fit right in.
Moseley and Periodic Law 1911 – Henry Moseley Working with spectra of 38 metals – elements fit into better patterns when organized according to nuclear charge. Led to : Modern definition of atomic number Periodic table organized according to atomic number instead of atomic mass Periodic Law : The physical and chemical properties of the elements are periodic functions of their atomic numbers.
The Modern Periodic table Define: arrangement of the elements in order of their atomic number so that elements with similar properties fall in the same column, or group.
The Noble Gases Most significant addition to periodic table 1894 – John William Strutt and Sir William Ramsey Discovered Argon
Periodicity Similar periodic pattern repeated with atomic number Difference in atomic number of similar properties 8, 8, 18, 18, 32 Difference in atomic number Atomic Number 2 8 10 8 18 18 36 18 54 32 86 3 8 11 8 19 18 37 18 55 32 87
Periodic Table songby Tom Lehrer There’s antimony, arsenic, aluminum, selenium, And hydrogen and oxygen and nitrogen and rheniumAnd nickel, neodymium, neptunium, germanium, And iron, americium, ruthenium, uranium, Europium, zirconium, lutetium, vanadium And lanthanum and osmium and astatine and radium And gold, protactinium and indium and gallium And iodine and thorium and thulium and thallium. There’s yttrium, ytterbium, actinium, rubidium And boron, gadolinium, niobium, iridium And strontium and silicon and silver and samarium, And bismuth, bromine, lithium, beryllium and barium. There’s holmium and helium and hafnium and erbium And phosphorous and francium and fluorine and terbium And manganese and mercury, molybdinum, magnesium, Dysprosium and scandium and cerium and cesium And lead, praseodymium, platinum, plutonium, Palladium, promethium, potassium, polonium, Tantalum, technetium, titanium, tellurium, And cadmium and calcium and chromium and curium. There’s sulfur, californium and fermium, berkelium And also mendelevium, einsteinium and nobelium And argon, krypton, neon, radon, xenon, zinc and rhodium And chlorine, cobalt, carbon, copper, Tungsten, tin and sodium. These are the only ones of which the news has come to Harvard, And there may be many others but they haven’t been discovered.