The Periodic Table Use the periodic table to determine the number of protons, neutrons, and electrons in an isotope of an element. Use the periodic table to identify the characteristics and properties of metals, non-metals, and metalloids.

Mendeleev Russian chemist in 1860s Arranged elements in rows with similar properties and increasing mass Left blanks for undiscovered elements

Modern Periodic Table Elements arranged by atomic number Periods-rows across the table Groups-columns (also called family) Periodic Law-pattern of repeating properties

Classes of Elements Metals Nonmetals Metalloids Majority of elements Left side of the table Transition metals Middle of the table Nonmetals Only 17 elements Right side of the table Metalloids Share properties of metals and nonmetals Stair step between metals and nonmetals Left to right, elements become less metallic and more nonmetallic

Alkali Metals Alkaline Earth Group 1 A Found only in compounds in nature Reactivity increases as you go down the row Have only 1 valence electron Li, Na, K, Rb, Cs, Fr http://www.open.edu/op enlearn/science-maths- technology/science/chemi stry/alkali-metals Group 2 A Harder than Alkali Metals Reactivity increases as you go down the row Have only 2 valence electron Be, Mg, Ca, Sr, Ba, Ra

Transition Metals Lanthanides and Actinides Found in the middle Make colored compounds Found at the bottom Many radioactive and man-made Called rare earth metals

Boron Carbon Nitrogen Oxygen Group 4A Group 3A 4 valence electrons B, Al, Ga, In, Tl Group 4A 4 valence electrons C, Si, Ge, Sn, Pb Nitrogen Oxygen Group 5A 5 valence electrons N, P, As, Sb, Bi Group 6A 6 valence electrons O, S, Se, Te, Po

Halogens Noble Gases Group 7A Group 8A 7 valence electrons React easily with metals F, Cl, Br, I, At Group 8A 8 valence electrons Extremely unreactive Colorless, odorless He, Ne, Ar, Kr, Xe, Rn