The Periodic Table

Early Periodic Table Simplest arrangement was by atomic weight Most significant relationships though have nothing to do with weight but how they react with each other Arrangement by reactivity shows that there is a relationship among atomic weights but its periodic (repeats every 7th element)

Periodic Law When elements are arranged by atomic number (# of p+) there is a repetition of chemical and physical properties

Representative Elements Modern Periodic Table Organized in columns called groups or families Rows are called periods Group A – representative elements (1A-7A) Group B - transition elements (1B-8B) Representative Elements (Group A) Representative Elements (Group A) Transition Elements (Group B)

Classification of Elements

Metals Properties shiny, smooth, solids (except mercury) Good conductors of heat and electricity High densities, melting/boiling points Malleable – bent or pounded into sheets Ductile – drawn into wires

Nonmetals Properties Gases or brittle, dull looking solids Poor conductors of heat and electricity Usually have lower densities, melting point, and boiling point than metals sulfur

Metalloids (Semimetals) Physical and chemical properties similar to both metals and nonmetals They are metallic-looking brittle solids Relatively good electrical conductivity.

Electron Configurations for Alkali Metals [He]2s1 [Ne]3s1 [Ar]4s1 [Kr]5s1 Lithium 1s22s1 Sodium 1s22s22p63s1 Potassium 1s22s22p63s23p64s1 Rubidium 1s22s22p63s23p64s23d104p65s1

Electron Configurations for Alkaline Earth Metals Beryllium 1s22s2 Magnesium 1s22s22p63s2 Calcium 1s22s22p63s23p64s2 Strontium 1s22s22p63s23p64s23d104p65s2 [He]2s2 [Ne]3s2 [Ar]4s2 [Kr]5s2

Electron Configuration for Noble Gases He – 1s2 Ne – 1s22s22p6 Ar – 1s22s22p63s23p6 Kr - 1s22s22p63s23p64s23d104p6

Ground State Electron Configurations of the Elements ns2np6 Ground State Electron Configurations of the Elements ns1 ns2np1 ns2np2 ns2np3 ns2np4 ns2np5 ns2

Valence Electrons Electrons in the outermost s and p orbitals (highest n shell) These electrons participate in chemical reactions

Reactivity of Elements Atoms in the same group have similar chemical properties because they have the same number of valence electrons

Octet Rule Atoms gain, lose, or share electrons to acquire a full set of eight valence electrons (to be like a noble gas) Eight is great!!!