Periodic Table History History of the Periodic Table

Periodic Table History

History of the Periodic Table Mendeleev – father of modern periodic table ¥left spaces for undiscovered elements & predicted properties of those elements ¥credited with discovering periodicity

History of the Periodic Table 2 Questions: 1. Why could most elements be arranged by increasing atomic mass, but a few could not? 2. What was the reason for chemical periodicity?

History of the Periodic Table Mosely ¥ shooting electrons at various metals to produce X-rays • frequencies of the X-rays were unique to the metals • assigned a whole number to each element → atomic numbers

History of the Periodic Table Mosely ¥ shooting electrons at various metals to produce X-rays • arrange elements by atomic numbers to get families with similar properties

Periodic Table Information

Periodic Table Information Periodic Table ¥an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column (group/family)

Periodic Table Information Periodic Law ¥the physical and chemical properties of elements are periodic functions of their atomic numbers

Types of Elements

Periodic Table Information Types of elements: ¥Metal – lustrous, good conductors, most are solids, malleable, ductile ¥Nonmetal - poor conductors, no luster, neither malleable nor ductile, most are gases, wide variety of other physical properties ¥Metalloid (aka semiconductors) properties of metals & non-metals

Parts of the Periodic Table

Periodic Table Information Period ¥ horizontal rows of elements Group (family) ¥ vertical columns of elements with the same number of valence electrons ¥valence electrons are the ones in the outermost shell and are the ones that are involved in making ions

Periodic Table Information Groups (families) ¥ alkali metals – group 1 (except hydrogen), VERY reactive, 1 valence electron ¥ alkaline earth metals – group 2, reactive, but not as much as group 1, 2 valence electrons ¥ transition metals – all of the elements in groups 3 -12, more stable than groups 1 -2 ¥ inner transition metals – all of the elements block containing #57 -70 and #89102

Periodic Table Information Groups (families) ¥ metalloids – elements that border the “staircase” ¥ halogens – group 17, most reactive group of nonmetals, 7 valence electrons ¥ noble gases – group 18, elements with filled outer shells of electrons, generally nonreactive or inert, 8 valence electrons (except He which has only 2)