Patterns exist everywhere – Patterns exist everywhere –. They occur in regular occurring shapes & structures and in repeating events & relationships. Scientists seek explanations for observed patterns and for the similarity and diversity within them. Patterns

Dmitri Mendeleev Father of Periodic 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. 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 included information about the elements physical and chemical properties. He looked for clues about how those elements compared to each other. He studied the patterns of the elements. 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 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. 2

Mendeleev’s Periodic Tables Notice the gaps that he was not able to fill in. He predicted the atomic mass of new elements that would later be found! The table at the left was The table at the right was Mendeleev’s first sketch the table that Mendeleev Of the periodic table. published in 1869.

Alien Periodic Table Horizontal Patterns: *Number of fingers increased by one. *The body shape was all the same. *They all had their first four fingers on their left hand. When there was more than four fingers, they had a right arm and hand. Vertical Patterns: *They had a characteristic that grew by one. (horns, hair, foot length, stripes, hat, hair length, tufts, number or legs) *They all had the same number of fingers. * Body shape progressed from triangle to circle to rectangle to oval to upside-down triangle.

Alien Periodic Table Horizontal Pattern; All of the aliens in the period have the same body shape.

Current Periodic Table Horizontal Pattern: All of atoms in the same period(row) have the same number of energy levels or shells of electrons.

Alien Periodic Table Horizontal Pattern: *They all had their first four fingers on their left hand. When there was more than four fingers, they had a right arm and hand.

Current Periodic Table Periodic Pattern: The first shell or energy level must be filled with two electrons before there is a second shell.

Alien Periodic Table Horizontal Pattern *Number of fingers increased by one going across.

Current Periodic Table Horizontal Pattern: 2. The number of outside or “valence” electrons increases by one as you move across the period(row).

Alien Periodic Table Vertical Pattern: The aliens all have the same number of fingers.

Current Periodic Table Vertical Pattern: 3. The atoms in the same vertical columns, “groups”, all have the same number of outside or “valence” electrons (1-8) except Helium that is full with two.

Alien Periodic Table Vertical Pattern: They had a characteristic that grew by one. (horns, hair, foot length, stripes, hat, hair length, tufts, number or legs)

Current Periodic Table Vertical Pattern: 4. As you move down the group, the number of energy levels or shells of electrons increases by one.

Alien Periodic Table Vertical Pattern: They had similar characteristics on their heads and bodies.

Current Periodic Table Vertical Pattern: 5. Elements in each group have similar characteristics due to their structure. They have similar physical and chemical properties.

Physical Properties of the Periodic Table Group two elements are known as the alkaline earth metals. They are all silver-colored and soft, and have relatively low densitiesGroup two elements are known as the alkaline earth metals. They are all silver-colored and soft, and have relatively low densities, melting pointsGroup two elements are known as the alkaline earth metals. They are all silver-colored and soft, and have relatively low densities, melting points, and boiling points.

Chemical Properties of the Periodic Table Group 17 elements are called halogens. They are extremely reactive. Due to their e high reactivity (electronegativity), they are not found in their elemental form in any natural environment on Earth. They are generally toxic, or even lethal, to biological organisms in their elemental forms. Fluorine Chlorine Bromine Iodine Astatine