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The Periodic Table

The Periodic Table. What does the word PERIODIC mean?. Why are the days of the week described as being periodic? Open book to page 194 and read the first two paragraphs. Periodic = happening at regular intervals or in a pattern. Discovering a pattern.

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The Periodic Table

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  1. The Periodic Table

  2. What does the word PERIODIC mean? • Why are the days of the week described as being periodic? • Open book to page 194 and read the first two paragraphs. • Periodic = happening at regular intervals or in a pattern

  3. Discovering a pattern • Mendeleev created the first periodic table of the elements in 1869. • Mendeleev arranged the elements in order of increasing atomic mass. Elements with similar properties fell into a repeating pattern. • He used his table to predict that elements with certain properties would be discovered later.

  4. Changing the pattern • Moseley determined the number of protons—the atomic number—in an atom. He then rearranged the periodic table by placing the elements in order of increasing atomic number. • Horizontally, elements are in order of increasing atomic number. Vertically, elements with similar chemical properties are grouped in columns.

  5. Classes of Elements • Elements are classified according to their properties as metals, nonmetals, and metalloids. • The zigzag line on the periodic table helps you locate the metals, nonmetals, and metalloids. • PERIODIC TABLE VIDEO

  6. Metals • Most elements are metals. Metals are located to the left of the zigzag line. • Most metals are shiny, malleable, and conduct electric current.

  7. Nonmetals and Metalloids • Nonmetals are located to the right of the zigzag line. Many properties of nonmetals are the opposite of the properties of metals. • Metalloids, also called semimetals, border the zigzag line. Metalloids have some properties of metals and some of nonmetals.

  8. Decoding the Periodic Table • SQUARES: Each square on the periodic table includes an element’s name, chemical symbol, atomic number, and atomic mass. • PERIOD: Each horizontal row of elements (from left to right) is called a period.

  9. Decoding cont. • GROUPS: Each vertical column of elements (from top to bottom) is called a group, or family. • Elements in the same group often have similar chemical and physical properties.

  10. The Periodic Law • The periodic law states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements. • All atoms of the same element have the same number of protons in the nucleus. Atoms that have the same number of protons but different numbers of neutrons are called isotopes.

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