Arranging Elements 12 1 Mendeleev and patterns Mendeleev

Arranging Elements 12. 1

Mendeleev and patterns • Mendeleev originally organized elements by atomic mass and saw certain characteristics repeating at periodic intervals • Periodic Law states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements. • Periodic table arrangement was altered to arrange elements by atomic number

Periodic Table and Classes of Elements • Information given on periodic table: atomic number, atomic mass, chemical symbol, element class and element name • Metals: shiny, malleable, ductile and good conductors of heat and electricity • Metalloids: have characteristics of both metals and nonmetals; it may be shiny but brittle and it may be a good conductor of heat and electricity • Nonmetals: dull, brittle, and poor conductor of heat and electricity

Periods and Groups • Chemical symbols begin with a capital letter. If there is more than one letter in the symbol it is lower case. • Periods – rows on the periodic table. Properties such as reactivity and conductivity change gradually from left to right. Shows the number of electron shells in the atoms on that row. • Groups – Columns on the periodic table. Elements in a group share certain properties, one of which is the number of electrons or electron vacancies on the outermost shell.