The Periodic TableThe Periodic Table

The The

BeginningBeginning

In the late 1800’s, Dmitri Mendeleev, a In the late 1800’s, Dmitri Mendeleev, a Russian chemist, searched for a way to Russian chemist, searched for a way to organize the elements.organize the elements.

When he arranged all the elements know When he arranged all the elements know at the time in order of increasing atomic at the time in order of increasing atomic masses, he discovered a pattern.masses, he discovered a pattern.

In the periodic table, the elements are In the periodic table, the elements are arranged by increasing atomic number arranged by increasing atomic number and by changes in physical and chemical and by changes in physical and chemical properties.properties.

MendeleevMendeleev

Mendeleev had to leave blank spaces in his Mendeleev had to leave blank spaces in his periodic table to keep the elements properly periodic table to keep the elements properly lined up according to their chemical properties.lined up according to their chemical properties.

From this information, he was able to predict the From this information, he was able to predict the properties and mass number of new elements properties and mass number of new elements that had not yet been discovered . that had not yet been discovered .

Two elements that he predicted about were Two elements that he predicted about were gallium and scandium.gallium and scandium.

GalliumGallium

Gallium wasn’t physically discovered till Gallium wasn’t physically discovered till after Mendeleev's death, but Mendeleev after Mendeleev's death, but Mendeleev did predict that it was there even though did predict that it was there even though he never saw it.he never saw it.

The ImprovementThe Improvement

In 1913, the work of Henry G.J. Mosley led to In 1913, the work of Henry G.J. Mosley led to the arrangement of elements based on their the arrangement of elements based on their increasing atomic numbers instead of an increasing atomic numbers instead of an arrangement based on the atomic mass.arrangement based on the atomic mass.

Reason – Cobalt/Nickel – The mass decreases Reason – Cobalt/Nickel – The mass decreases from left to right while the atomic number from left to right while the atomic number increases.increases.

Why? – Fewer Neutrons in Nickel that cobalt.Why? – Fewer Neutrons in Nickel that cobalt.

What we use todayWhat we use today

This is the current method that we use This is the current method that we use today; increasing today; increasing atomic numberatomic number from from right to left.right to left.

The Atom and the periodic TableThe Atom and the periodic Table

Objects often are sorted or grouped Objects often are sorted or grouped according to the properties they have in according to the properties they have in common. common.

The vertical columns in the periodic table The vertical columns in the periodic table are called are called groups groups or or families families. .

Groups are numbered 1-18 at the top of Groups are numbered 1-18 at the top of the periodic table. Elements in each group the periodic table. Elements in each group have similar properties.have similar properties.

Group 1Group 1

This family has all the This family has all the same propertiessame properties. . Group 1 has only Group 1 has only one valence electron in one valence electron in the outer shellthe outer shell..

Look at Group 11. They are all shiny Look at Group 11. They are all shiny metals and conduct electricity. (same metals and conduct electricity. (same properties) (same number of valence properties) (same number of valence electrons.)electrons.)

Electron Cloud StructureElectron Cloud Structure

In a neutral atom, the number of In a neutral atom, the number of protonsprotons equals (=) the number of equals (=) the number of electrons.electrons.

Scientists have found that electrons within Scientists have found that electrons within the electron cloud have different amounts the electron cloud have different amounts of energy. We make models of the of energy. We make models of the electrons by placing the electrons in electrons by placing the electrons in energy levelsenergy levels

Energy LevelsEnergy Levels

Energy levels nearer the nucleus have Energy levels nearer the nucleus have lower energy than those levels that are lower energy than those levels that are father away.father away.

Valance ElectronsValance Electrons

Elements in the same Elements in the same groupgroup have the have the same number of electrons in their outer same number of electrons in their outer energy level. energy level.

It is the number of electrons in the outer It is the number of electrons in the outer energy level that determines the chemical energy level that determines the chemical properties of the element.properties of the element.

Energy LevelsEnergy Levels

There are 7 energy levels.There are 7 energy levels. Energy level 1 can only contain 2 electronsEnergy level 1 can only contain 2 electrons Energy level 2 can only contain 8 electrons.Energy level 2 can only contain 8 electrons. Energy level 3 can only contain 18 electrons.Energy level 3 can only contain 18 electrons. Energy level 4 can only contain 32 electrons.Energy level 4 can only contain 32 electrons. A complete and stable outer energy level will A complete and stable outer energy level will

contain 8 electrons.contain 8 electrons.

RowsRows

Rows, also know as Rows, also know as periodsperiods, move in a , move in a horizontal direction.horizontal direction.

As you move from right to left on the As you move from right to left on the periodic table, each element will add an periodic table, each element will add an electron to the outermost level until it electron to the outermost level until it reaches its capacity and stars over on a reaches its capacity and stars over on a new energy level.new energy level.

Electron Dot DiagramElectron Dot Diagram

An electron dot diagram uses the symbol An electron dot diagram uses the symbol of the element and dots to represent the of the element and dots to represent the electrons in their outer energy level.electrons in their outer energy level.

Electron dot diagrams are used also to Electron dot diagrams are used also to show hoe the electrons in the outer energy show hoe the electrons in the outer energy level are bonded when element combine level are bonded when element combine to form compounds.to form compounds.

Example:Example:

Hydrogen atom as 1 valence electron.Hydrogen atom as 1 valence electron.

A Fluorine atom has 7 valence electronsA Fluorine atom has 7 valence electrons

Give the following electron dot Give the following electron dot diagrams.diagrams.

Na Pb Ne XeNa Pb Ne Xe

C N O FC N O F

Notices what happens as you move across the periodic Notices what happens as you move across the periodic table .table .

Same Group – Similar PropertiesSame Group – Similar Properties

The elements in Group 17, the halogens, have The elements in Group 17, the halogens, have electron dot diagrams similar to chlorine.electron dot diagrams similar to chlorine.

ClCl

All halogens have seven electron in their outer All halogens have seven electron in their outer energy level, all group members will undergo energy level, all group members will undergo chemical reactions in similar ways.chemical reactions in similar ways.

Let’s come together!Let’s come together!

A common property of halogens is the A common property of halogens is the ability to form compounds with elements in ability to form compounds with elements in group 1.group 1.

Na ClNa Cl

Na ClNa Cl

Not all element will combine with Not all element will combine with other elements.other elements.

The elements in The elements in Group 18 – the Noble Group 18 – the Noble GasesGases

The elements in Group 18 have completed The elements in Group 18 have completed outer energy levels. This special outer energy levels. This special configuration makes Group 18 configuration makes Group 18 relatively relatively unreactive.unreactive.

Group 18 ElementsGroup 18 Elements Write the correct name for the element.Write the correct name for the element.

He - He - Ne - Ne - Ar - Ar - Kr - Kr - Xe - Xe - Rn -Rn -

Regions of the Periodic TableRegions of the Periodic Table

The periodic table has several regions with The periodic table has several regions with specific names.specific names.

The horizontal rows of elements on the The horizontal rows of elements on the periodic table are called periodic table are called PeriodsPeriods (The (The number of energy levels)number of energy levels)

The Periodic Table is broken down The Periodic Table is broken down into 3 parts.into 3 parts.

Metals – (largest portion) ( mainly left side Metals – (largest portion) ( mainly left side and middle) (75%)and middle) (75%)

Non-Metals – (gases) (Right side) (18%)Non-Metals – (gases) (Right side) (18%)

Metalloids – (smallest group) (semimetals) Metalloids – (smallest group) (semimetals) Located between metals and nonmetals.Located between metals and nonmetals.

Elements in the UniverseElements in the Universe

Are all of the elements throughout the Are all of the elements throughout the universe the same?universe the same?

Using the technology that is available Using the technology that is available today, scientists are finding the same today, scientists are finding the same elements throughout the universe.elements throughout the universe.

98% of the universe is made of hydrogen98% of the universe is made of hydrogen