Dmitri Mendeleev is considered the father of the periodic table. In 1869, he created one of the first recognizable periodic tables that arranged elements based on increasing atomic mass. It included 17 columns with gaps for elements not yet discovered. Later, in 1871, he revised his table to include 8 columns and more accurately predicted properties of undiscovered elements. Today's periodic table arranges elements by atomic number instead of mass and includes all known elements. It categorizes them into metals, nonmetals, and metalloids based on their physical and chemical properties.

1. Michael Hadsell Jessica Swift THE PERIODIC TABLE OF ELEMENTS

2. HISTORY OF PERIODIC TABLE OF ELEMENTS The First Attempt: -The periodic table of elements was first attempted to be made by a French geologist, A.E.Beguyer de Chancourtois. He positioned elements according to increasing atomic weight. -The “Father” of the Periodic Table: -Chemists Lothar Meyer and Dmitri Mendeleev were both working during the same time period to create the periodic table of elements. They were both producing similar results, but they were working completely independent of each other. -Unfortunately for Meyer, Mendeleev’s periodic table was available for the community before Meyer’s. Dmitri Mendeleev

3. -Mendeleev's periodic table of 1869 contained 17 columns with two partial periods of seven elements each. - In 1871 Mendeleev revised the 17-group table with eight columns. -The table contained gaps because Mendeleev predicted the discovery of new elements. -Unlike the modern periodic table, Mendeleev’s was arranged in order by increasing atomic mass. Today the elements are correctly arranged by increasing atomic number.

4. This is Mendeleev’s Periodic table after he revised it in 1871, adding the 8 th group.

5. This is the modern Periodic Table of Elements used today all around the world.

6. -Henry Moseley later found that the properties of elements depend on the structure of their atoms and vary with atomic numbers in a systematic way. This was used to make the modern periodic table of elements. -The atomic number is the same as the number of protons in an atom’s nucleus. -In the periodic table of elements, the elements are put into periods and groups.

7. Period: Periods are the horizontal rows in the periodic table. The number of the period is the same as the number of electrons in the outermost electron orbital of an element in that period. Group: Groups are the vertical columns in the periodic table. Elements in the same group have similar properties.

8. -There are three types of elements in the periodic table of elements. The three types are Metals, Non-Metals, and Metalloids. Physical Properties of Metals: -Luster (shininess) -Good conductors of heat and electricity -High density (heavy for their size) -High melting point -Ductile (most metals can be drawn out into thin wires) -Malleable (most metals can be hammered into thin sheets) Chemical Properties of Metals: -Easily lose electrons -Corrode easily.

9. Nonmetals Nonmetals are found to the right of the stair step line. Their characteristics are opposite those of metals. Physical Properties of Nonmetals: -No luster (dull appearance) -Poor conductor of heat and electricity -Brittle (breaks easily) -Not ductile -Not malleable -Low density -Low melting point Chemical Properties of Nonmetals: -Tend to gain electrons Since metals tend to lose electrons and nonmetals tend to gain electrons, metals and nonmetals like to form compounds with each other. These compounds are called ionic compounds. When two or more nonmetals bond with each other, they form a covalent compound.

10. Since metals tend to lose electrons and nonmetals tend to gain electrons, metals and nonmetals like to form compounds with each other. These compounds are called ionic compounds . When two or more nonmetals bond with each other, they form a covalent compound. -The group of gases on the right edge of the table are known as noble Gases or inert gases. Noble gases -Chemically nonreactive (This is because they have a complete valence shell.) -Little tendency to gain or lose electrons. -Low boiling points (all are gases at room temperature)

11. Metalloids Elements on both sides of the zigzag line have properties of both metals and nonmetals. These elements are called metalloids. Physical Properties of Metalloids: -Solids -Can be shiny or dull -Ductile -Malleable -Conduct heat and electricity better than nonmetals but not as well as metals

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