The Periodic Table  Arrangement of elements based on properties –Dmitri Mendeleev  Mid 1800’s  Arranged elements by increasing atomic mass  Left blanks for undiscovered elements –Henry Moseley  1913  Arranged by atomic number

Mendeleev Sing along with the chorus! Who told the elements where to go? Mendeleev! Who put them into columns and in rows? Mendeleev! Who was ready, who was able to make a periodic table, Who was that chemist? Mendeleev!

 Periods- Horizontal rows –Just numbered –Gives rise to the Periodic Law – that when the elements are arranged in increasing atomic number there are properties that repeat themselves.  Groups or Families – Vertical columns –Arranged by similar properties –Representative Elements = Groups 1A to 7A and 0 (tall columns)

 Metals – Ductile, malleable, luster and high conductivity –Alkali Metals – Group 1A –Alkali Earth Metals – Group 2A –Transition Metals – Groups 3B to 2B (Short Columns) –Inner Transition Elements – Two Rows that are separate. (Also called the rare Earth elements) –80% of all elements are metals

 Nonmetals – Non-lustrous, poor conductors, brittle, some are gases –Halogens – Group 7A –Noble Gases – Group 0  Inert – Undergo few chemical reactions –The other nonmetal groups are named for the element that they start with. Example: Oxygen Family.  Metalloids – Elements that share properties with the metals and the nonmetals. –Found on the “stair-step” line.