Periodicity Notes Pgs.

Dimitri Mendeleev produced the first useful and widely accepted periodic table Elements were arranged according to increasing atomic mass  A repetition in properties was noticed Development of the Modern Atomic Table

How is the modern periodic table arranged?  By atomic number Development of the Modern Atomic Table

Henry Mosely discovered that each element has a unique number of protons in their nucleus – this is the atomic mass. Mosely noticed that arranging elements by increasing atomic mass put some elements in the wrong column… He decided to place them by increasing atomic number and that put all the elements in the correct column. Development of the Modern Atomic Table

Periodic Law There is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number.

Periodic Table Lingo Groups or families = columns (vertical) Periods = rows (horizontal) Metals = elements on the left side Nonmetals = elements on the right side  Hydrogen is considered a nonmetal Metalloids = elements with properties like metals and nonmetals (zig-zagging between metals and nonmetals)

Periodic Table Lingo The periodic table is divided into two big groups Group A – Called the Representative Group Group B – Called the Transition Group

Periodic Table Lingo Each element in a group (or family) has similar chemical properties Each element in a group (or family) has the same number of valence electrons

Representative Groups ALKALI METALS – Group 1 ALKALINE EARTH METALS – Group 2 METALS – Parts of Groups METALLOIDS METALLOIDS – Parts of Groups NONMETALS – Parts of Groups HALOGENS – Group 17 (salt formers) NOBLE (INERT) GASES – Group 18

Transition Groups TRANSITION METALS – Group LANTHANIDE SERIES – In Period 6 ACTINIDE SERIES – In Period 7

State of Elements Most elements are in the solid state at standard pressure and room temperature Exceptions:  Liquids – Hg, Br  Gasses – N, O, F, H, He, Ne, Ar, Kr, Xe, Rn

Physical Properties of Metals Luster (shiny) Ductile (can be drawn into long wires) Malleable (can be hammered into thin sheets) Good conductors of heat and electricity High Density High melting and boiling points

Chemical Properties of Metals Corrode easily (rusting or tarnishing) Lose electrons easily The most reactive family of metals is alkali metals (group 1) The most reactive metal is Francium

Physical Properties of Nonmetals Usually a gas No luster (dull) Brittle (breaks easily) Insulators (bad conductors of heat and electricity) Not ductile Not malleable Low density Low melting point

Chemical Properties of Nonmetals Tend to gain electrons The most reactive family of nonmetals is halogens (group 17) The most reactive nonmetal is Flourine

Physical Properties of Metalloids Elements on both side of the stair step have properties of both metals and nonmentals  Solids  Can be shiny or dull  Ductile  Malleable  Conduct heat and electricity better than nonmetals but not as well as metals

Valence Electrons The electrons in the outermost energy level of an atom are the ones involved in chemical reactions.

GroupGroup NumberNumber of Valence Electrons Alkali metals 11 Alkaline earth metals 22 Boron family 133 Carbon family 144 Nitrogen family 155 Oxygen family 166 Halogens 177 Noble Gasses 188 (except He – 2) Valence Electrons

Elements in the same group have similar properties because they have the same number of valence electrons The period of an element indicated the energy level of the valence electrons

Octet Rule In order to be stable, atoms tend to gain or lose electrons in order to have 8 electrons in their valence energy level  Like the noble gasses