The Periodic Table 2 NOTES 6 Organizing the

“The Periodic Table 2” NOTES #6

Organizing the Elements u. A few elements have been known for thousands of years - since ancient times u As more were discovered, chemists realized they needed a way to organize the elements.

Organizing the Elements u. Chemists used the properties of elements to sort them into groups.

Mendeleev’s Periodic Table u. Mendeleev Arranged elements in order of increasing atomic mass u. The first “Periodic Table”

Mendeleev u. He left blanks for yet undiscovered elements u. But, there were problems: • Such as Co and Ni; Ar and K; Te and I

A better arrangement u. In 1913, Henry Moseley – arranged elements according to increasing atomic number u. The arrangement used today

The Periodic Law says: uthere is a periodic repetition of their physical and chemical properties. u. Horizontal rows = periods • There are 7 periods u. Vertical column = group (or family) • Similar physical & chemical prop. • Identified by number(1 -18)

18 Be F B Transition metals Sc 17 61 15 14 2 13 1 H Al Si Ge As Sb Te Fr La Po At Ac Metalloids Rare-Earth or Inner transition metals He

Areas of the periodic table u Three classes of elements are: 1) metals, 2) nonmetals, and 3) metalloids 1) Metals: electrical conductors, have luster, ductile, malleable 2) Nonmetals: generally brittle and non-lustrous, poor conductors of heat and electricity

Metallic Character ¨ Metals ¨ Nonmetals ¨ Metalloids

Areas of the periodic table Notice the stair-step line? 3) Metalloids: border the line-2 sides • Properties are intermediate between metals and nonmetals u

Squares in the Periodic Table The periodic table displays the symbols and names of the elements

Groups of elements - family names u. Group I – alkali metals • Forms a “base” (or alkali) when reacting with water • Group 2 – alkaline earth metals u. Group 17 – halogens • Means “salt-forming”

Groups Noble gases are the elements in Group 18 they rarely take part in a reaction; very stable = don’t react

Group 1 are the alkali metals (but NOT H) Group 2 are the alkaline earth metals H

u Group 18 are the noble gases u Group 17 is called the halogens

Be F B Transition metals Sc Al Si Ge As Sb Te Fr La Po At Ac Metalloids Rare-Earth or Inner transition metals 18 A Noble Gases 17 Halogens 61 15 14 13 2 Alkaline earth metals 1 Alkali metals H He