Patterns exist Patterns exist everywhere –. They everywhere –. They occur in regular occur in regular occurring shapes & occurring shapes & structures and in structures and in repeating events &repeating events &

relationships.relationships.

Scientists seek Scientists seek explanations for explanations for observed observed patterns and for patterns and for the similarity and the similarity and diversity within diversity within them. them.

Dmitri MendeleevDmitri Mendeleev Father of Periodic Table Father of Periodic Table

In 1869, Dmitri Mendeleev decided on a plan to organize the elements. In 1869, Dmitri Mendeleev decided on a plan to organize the elements. He wrote facts about all of the known elements on paper cards.He wrote facts about all of the known elements on paper cards. He included information about the elements physical and chemical properties.He included information about the elements physical and chemical properties. He looked for clues about how those elements compared to each other.He looked for clues about how those elements compared to each other. He studied the patterns of the elements.He studied the patterns of the elements. He was able to organize the elements at the time in order of their atomic mass.He was able to organize the elements at the time in order of their atomic mass. He realized that the physical and chemical properties of elements were related to He realized that the physical and chemical properties of elements were related to

their atomic mass in a ‘periodic’ way. He arranged them so that groups of their atomic mass in a ‘periodic’ way. He arranged them so that groups of elements with similar properties fell into vertical columns in his table.elements with similar properties fell into vertical columns in his table.

For many years scientists had been struggling to come up with patterns in the elements. Elements are a substance that cannot be broken down. Mendeleev was creating his table before the time when detailed discoveries about the atom had been conducted.

Mendeleev’s Periodic TablesMendeleev’s Periodic Tables

The table at the left wasThe table at the left was The table at the right wasThe table at the right was

Mendeleev’s first sketch Mendeleev’s first sketch the table that Mendeleevthe table that Mendeleev

Of the periodic table.Of the periodic table. published in 1869.published in 1869.

Notice the gaps that he was not able to fill in. He predicted the atomic mass of new elements that would later be found!

Alien Periodic TableAlien Periodic Table

Horizontal PatternsHorizontal Patterns::

*Number of fingers increased by *Number of fingers increased by one. one.

*The body shape was all the same.*The body shape was all the same.

*They all had their first four fingers *They all had their first four fingers on their left hand. When there was on their left hand. When there was more than four fingers, they had a more than four fingers, they had a right arm and hand.right arm and hand.

Vertical Patterns:Vertical Patterns:

*They had a characteristic that *They had a characteristic that grew by one. (horns, hair, foot grew by one. (horns, hair, foot length, stripes, hat, hair length, length, stripes, hat, hair length, tufts, number or legs)tufts, number or legs)

*They all had the same number of *They all had the same number of fingers. fingers.

* Body shape progressed from * Body shape progressed from triangle to circle to rectangle to triangle to circle to rectangle to oval to upside-down triangle.oval to upside-down triangle.

Current Periodic TableCurrent Periodic Table

The table is organized from top to bottom and left to right by the number of protons.The table is organized from top to bottom and left to right by the number of protons. The table is organized from top to bottom and left to right by the atomic mass.The table is organized from top to bottom and left to right by the atomic mass.

Groups and PeriodsGroups and Periods 18 vertical columns called 18 vertical columns called GROUPSGROUPS or or

FAMILIESFAMILIES Elements in each group have similar Elements in each group have similar

characteristics.characteristics. Elements share similar physical and chemical Elements share similar physical and chemical

properties.properties. 7 horizontal rows called 7 horizontal rows called PERIODSPERIODS

Series of different elements that are not alike Series of different elements that are not alike but they have progressive patterns.but they have progressive patterns.

Pattern from left to right is reactive to non-Pattern from left to right is reactive to non-reactive. reactive.

Physical Properties of the Physical Properties of the Periodic TablePeriodic Table

Group two elements are known as the alkaline Group two elements are known as the alkaline earth metals. They are all silver-colored and earth metals. They are all silver-colored and soft, and have relatively low soft, and have relatively low densities, , melting points, and , and boiling points..

Chemical Properties of the Chemical Properties of the Periodic TablePeriodic Table

Group 17 elements are called halogens. They are extremely Group 17 elements are called halogens. They are extremely reactive. Due to their e high reactivity (electronegativity), reactive. Due to their e high reactivity (electronegativity), they are not found in their elemental form in any natural they are not found in their elemental form in any natural environment on Earth. They are generally toxic, or even environment on Earth. They are generally toxic, or even

lethal, to biological organisms in their elemental formslethal, to biological organisms in their elemental forms..

*The number of the period indicates how many electron orbitals there are in each atom.*The number of the period indicates how many electron orbitals there are in each atom.

*As you move across the period, the number of electrons in the outermost orbital increases *As you move across the period, the number of electrons in the outermost orbital increases by one.by one.

*In a group, the outermost orbital has the same number of electrons.*In a group, the outermost orbital has the same number of electrons.

*Because electrons are the outermost particles in an atom, they are the ones that give an *Because electrons are the outermost particles in an atom, they are the ones that give an atom it’s properties, so atom it’s properties, so elements with similar outer orbitals, have similar propertieselements with similar outer orbitals, have similar properties

Group 1 - Has one outside electrons. They are very reactive metals that react violently with water.Group 1 - Has one outside electrons. They are very reactive metals that react violently with water.

Group 2 – Have two outside electrons. They are soft, silver metals that are reactive with oxygen.Group 2 – Have two outside electrons. They are soft, silver metals that are reactive with oxygen.

Group 17 – Have 7 outside electrons. They are very reactive nonmetals.Group 17 – Have 7 outside electrons. They are very reactive nonmetals.

Group 18 – Have 8 outside electrons. They are very nonreactive gases. (noble gases)Group 18 – Have 8 outside electrons. They are very nonreactive gases. (noble gases)