History of the Periodic Table

The Beginning… In Chemistry, we have organized the elements that compose our world into the Periodic Table of Elements The word periodic means “repeated in a pattern”

Dmitri Mendeleev Dmitri Mendeleev (1869, Russian) Started with 63 known elements Organized elements based on similar properties. Organized elements by increasing atomic mass.

Dmitri Mendeleev Predicted the properties and atomic masses of unknown elements where there were empty spaces. His pattern formed columns where all of the elements in the columns showed similar physical and chemical properties

Henry Mosely Henry Mosely (1913, British) Organized elements by increasing atomic number. Fixed problems in Mendeleev’s arrangement.

Periodic Law States that the physical and chemical properties of the elements are periodic functions of their atomic numbers

The Periodic Table Organization

Terms Groups or Families – vertical columns Period – horizontal rows

Periodic Trends Group # = # of valence e- (except He) Families have similar properties. Period # = # of energy levels 1A 2A 3A 4A 5A 6A 7A 8A

The Period Table Naming

Columns & Rows Group 1 - Alkali Metals Group 2 - Alkaline Earth Metals Groups 3-12 – Transition Metals Group 13 - Boron Family Group 14 - Carbon Family Group 15 - Nitrogen Family Group 16 - Oxygen Family Group 17 - Halogens Group 18 - Noble Gases

Rare Earth Family Rare earth metals belong between families 3 and 4 They are typically below the rest of the table to save space

Table Sections Representative Elements Transition Metals Rare Earth Elements

Table Sections Overall Configuration Lanthanides - part of period 6 Actinides - part of period 7

The Periodic Table Periodic Trends

Periodic Trends Valence Electrons Increases as you move RIGHT

The periodic number tells you how many energy levels there are in an atom They do not have the same properties

Periodic Trends Energy Levels Increases as you move DOWN.

Periodic Trends Atomic Radius Increases to the LEFT and DOWN.

Be or Ba Ca or Br Ba Ca Periodic Trends Which atom has the larger radius? Be or Ba Ca or Br Ba Ca

Mass Number vs Atomic Mass Recall… The mass number is the sum of the protons and neutrons The Atomic mass is the average of the isotopic masses that exist based on its abundance

Diagrams Two types of diagrams are used to show the configuration of electrons in an atom

Bohr Shows all electrons in their different energy levels Dot Shows only the valence electrons (outermost energy level

Bohr Diagram Find your element on the periodic table Determine the number of electrons- It is the same as the atomic number for a neutral atom

Bohr Diagram Determine the number of energy levels it is the number of rows down the table

Bohr Diagram Higher energy levels hold more elctrons 1st energy level holds 2 electrons 2nd energy level holds 8 electrons This gives the periodic table its shape

Bohr Diagrams The electrons are represented by dots or the letter e, filling from inside out The number of energy levels are represented by rings

Dot Diagram Only the number of valence electrons are shown

Dot Diagram Determine the Group number and Determine the number of valence electrons Draw the dots around the symbol

Dot Diagrams Dots represent the valence e-. EX: Sodium EX: Chlorine

Metallic Character Metals Nonmetals Metalloids

Bellwork 10/19 Who arranged the PT by increasing atomic mass? Who arranged the PT by increasing atomic number? What are the vertical columns called? What are the horizontal rows called? Does a group or period give you the number of valence electrons? The number of energy levels? Where are the metals located? Nonmetals? Metalloids? What are some characteristics of Metals? Nonmetals?

Metals Located to the left of the “staircase” Physical Properties Luster – shiny Malleable – pounded into different shapes Ductile – stretched into wires Solid at room temperature (except Mercury) Good conductors of heat and electricity

Metals Continued Chemical Properties: Corrosive – gradual wearing away of a metal due to a chemical reaction Metal converted into a metallic compound Often lose electrons in a chemical reaction

Nonmetals Located to the right of the “staircase” Physical Properties: Dull in appearance Brittle – breaks apart easily Most are gasses at room temperature Poor conductor of heat and electricity

Nonmetals Continued Chemical Properties React with metals Gain Valence electrons Elements with 8 valence electrons do not react with other elements

Metalloids Border the “staircase” Have properties of both metals and nonmetals

Reactivity Chemical reactivity is a measure of how easily a substance combines with another substance

Reactivity It is related to bonding- oxidation An oxidation number of 0 has a filled orbital (it is already stable) Low oxidation number (+-1) are less energy than high ones(+-4)

Reactivity Metals and nonmetals are more reactive Reactivity for metals increase as you move left and down the periodic table Reactivity for nonmetals increase as you move right and up

Periodic Trends

Reactivity More reactive metal: Mg or Al? More reactive Metal: Na or Fr? More reactive Non-metal: B or O? More reactive Non metal: F or Br?