The Periodic Table and Periodic Law Chapter 6

Section 6.1: Development of the Modern Periodic Table Late 1790’s- Lavoisier compiled a list of 23 elements known at the time Late 1790’s- Lavoisier compiled a list of 23 elements known at the time By known elements By known elements John Newlands John Newlands Arranged elements by increasing atomic mass Arranged elements by increasing atomic mass Noticed properties repeated every eighth element (periodic) Noticed properties repeated every eighth element (periodic) Law of Octaves Law of Octaves

Dmitri Mendeleev Russian Russian 1 st periodic table 1 st periodic table Organized elements by properties Organized elements by properties Arranged elements by atomic mass Arranged elements by atomic mass Predicted existence of several unknown elements Predicted existence of several unknown elements Element 101 Mendeleevium (Md) Element 101 Mendeleevium (Md)

Henry Moseley 1913-performs experiments to determine the atomic number of the known elements 1913-performs experiments to determine the atomic number of the known elements Afterwards arranges the elements in the periodic table listing them by increasing atomic number instead of by mass Afterwards arranges the elements in the periodic table listing them by increasing atomic number instead of by mass

Periodic Law When the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

The Modern Periodic Table Groups- aka families (vertical columns) Groups- aka families (vertical columns) Each group is numbered 1-8 followed by the letter A or B Each group is numbered 1-8 followed by the letter A or B Representative Elements- designated with an A (1A-8A) Representative Elements- designated with an A (1A-8A) Transition Elements- designated with a B (3B-12B) Transition Elements- designated with a B (3B-12B) 18 total groups 18 total groups elements of any one group have similar physical and chemical properties elements of any one group have similar physical and chemical properties

Periods- horizontal rows Periods- horizontal rows 7 total periods 7 total periods element properties change as you go across each row element properties change as you go across each row the pattern of properties repeats from one period to the next the pattern of properties repeats from one period to the next

Classifying the Elements Three main classifications for the elements Three main classifications for the elements Metals Metals Nonmetals Nonmetals Metalloids Metalloids

Metals Physical Properties Physical Properties Luster (shininess) Luster (shininess) Good conductors of heat and electricity Good conductors of heat and electricity High density (heavy for their size) High density (heavy for their size) High melting point High melting point Ductile (most metals can be drawn out into thin wires) Ductile (most metals can be drawn out into thin wires) Malleable (most metals can be hammered into thin sheets) Malleable (most metals can be hammered into thin sheets) Chemical Properties Chemical Properties Easily lose valence electrons Easily lose valence electrons Corrode easily Corrode easily Alkali Metals- group 1A elements (except hydrogen) Alkali Metals- group 1A elements (except hydrogen) Alkaline Earth Metals- group 2A elements Alkaline Earth Metals- group 2A elements

Metals Con’t. Transition Metals Transition Metals Group B elements Group B elements Inner Transition Metals Inner Transition Metals Lanthanide- used as phosphors (substances that emit light when struck by electrons) Lanthanide- used as phosphors (substances that emit light when struck by electrons) Actinide Actinide

Nonmetals Physical Properties Physical Properties No luster (dull appearance) No luster (dull appearance) Poor conductor of heat and electricity Poor conductor of heat and electricity Brittle (breaks easily) or gaseous Brittle (breaks easily) or gaseous Not ductile Not ductile Not malleable Not malleable Low density Low density Low melting point Low melting point Bromine is the only nonmetal liquid at room temperature Bromine is the only nonmetal liquid at room temperature Chemical Properties Chemical Properties Tend to gain valence electrons Tend to gain valence electrons

Nonmetals Con’t Halogens Halogens Group 7A Group 7A Extremely Reactive Extremely Reactive Noble Gases Noble Gases Group 8A Group 8A Extremely Unreactive Extremely Unreactive

Metalloids Bordering the stair-step line Bordering the stair-step line Physical Properties Physical Properties Solids Solids Can be shiny or dull Can be shiny or dull Ductile Ductile Malleable Malleable Conduct heat and electricity better than nonmetals but not as well as metals Conduct heat and electricity better than nonmetals but not as well as metals

Elements in the same group on the periodic table have similar chemical properties because they have the same valence electron configuration Elements in the same group on the periodic table have similar chemical properties because they have the same valence electron configuration

Octet Rule- atoms tend to gain, lose or share electrons in order to acquire a full set of eight valence electrons Hydrogen and Helium are exceptions ( 2 V.E.) Determines the types of ions likely to form Elements on the right side tend to gain electrons Elements on the left side tend to lose electrons