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Arranging the elements


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Chemistry, periodic table

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Arranging the elements

  1. 1. Arranging the elements Order please!
  2. 2. Is there only one way to arrange things? • If we had a deck of cards, think of all the ways a deck of cards could be laid out so that the cards form some sort of identifiable pattern.
  3. 3. Dmitry Mendeleev • A Russian chemist , discovered a pattern to the elements in 1869. He finally arranged the elements according to their increasing atomic mass. • It is called the periodic table, because he noticed a pattern repeating every 7 elements.
  4. 4. Henry Moseley • In 1914, a British scientist who determined the number of protons (atomic number) in an atom. • All the elements fit the pattern in Mendeleev’s periodic table when they were arranged by the atomic number. • This produced the modern periodic table.
  5. 5. Usetheperiodictabletoanswerthefollowingquestions. Page 338 in textbook • How many elements are found in the periodic table? • Are there more metals or non metals in the periodic table? • How many periods are there? How many groups? • What information is shown by each square of the periodic table? • How many elements are liquid at room temperature? • How many elements are gas at room temperature?
  6. 6. The Periodic Table and Classes of Elements • Elements are classified as metals, nonmetals, and metalloids, according to their properties. • The number of electrons in the outer energy level of an atom is one characteristic that helps determine which category an element belongs in. • The zigzag line on the periodic table can help you recognize which elements belong in which category.
  7. 7. Metals • Metals are found to the left of the zigzag line. Atoms of most metals have few electrons in their outer energy level. • Metals tend to lose their electrons in their outer most shell to become stable, creating positive ions. • Most metals are • Shiny • Ductile • Malleable • Good conductors of electric current • Good conductors of thermal energy.
  8. 8. Nonmetals • Nonmetals are found to the right of the zigzag line. Atoms of most nonmetals have an almost complete set of electrons in their outer energy level. • Nonmetals tend to gain electrons to fill their outer most shells. Creating negative ions. • Nonmetals are • Dull • Brittle • Nonmalleable • Poor conductors of electric current • Poor conductors of thermal energy.
  9. 9. Metalloids • Metalloids are the elements that border the zigzag line. Atoms of metalloids have about half of a complete set of electrons in their outer energy level. • Metalloids have some properties of metals and some properties of nonmetals. • Metalloids are also called semiconductors.
  10. 10. Decoding the Periodic Table • Each Element is Identified by a Chemical Symbol. Each square on the periodic table includes an element’s name, chemical symbol, atomic number, and atomic mass. • For most elements, the chemical symbol has one or two letters. The newest elements have temporary three-letter symbols.
  11. 11. Columns and rows • Columns Are Called Groups Each vertical column of elements is called a group. Elements in the same group often have similar chemical and physical properties. • Rows Are Called Periods Each horizontal row of elements is called a period. The chemical and physical properties of elements in a row follow a repeating pattern as you move across the period.
  12. 12. Information found in each square Atomic number Number of protons in the atom Chemical symbol Consists of one or two letters first is capital. Element name Atomic mass Mass of nucleus (protons + neutrons)
  13. 13. Which of the following statements is correct for the elements shown? A. Lithium has the greatest atomic number. B. Sodium has the least atomic mass. C. Atomic number decreases as you move down the column. D. Atomic mass increases as you move down the column
  14. 14. Homework • Memorize the first 20 elements of the periodic table. • Solve HW sheet #2
  15. 15. Group 1: Alkali metals • Here atoms have one electron in their outermost shell, which makes it easy for the metal to lose its electron and become stable. That is why they are the most reactive metals. • Upon losing an electron the metal atom becomes a positively charged ion (+1). • They react violently with water producing hydrogen gas and a soluble alkaline hydroxide.
  16. 16. Group 2: Alkaline earth-metals • These have two electrons in their outer most level, which makes it a bit harder to lose than alkali metals; thus they are less reactive. They lose their 2 electrons and become positively charged (+2). •
  17. 17. Groups 3-12: Transition metals • These are metals that have 1 or 2 electrons in their outer most level. They are less reactive than alkali-earth metals. They have higher melting points and densities than groups 1 and 2. • They lose their electrons less easily so they are less reactive than alkali metals and alkaline-earth metals. • Properties: shininess, good conductors of electric current and thermal energy
  18. 18. Lanthanides and Actinides • Some transition metals from Periods 6 and 7 appear in two rows at the bottom of the periodic table. Elements in the first row are called lanthanides and elements in the second row are called actinides.
  19. 19. Group13: Boron group • Aluminum is the most common element from Group 13. Group 13 properties: • group contains one metalloid and five metals • 3 electrons in the outer level • reactive • solids at room temperature
  20. 20. Group 14: Carbon group • group contains one nonmetal, two metalloids, and two metals • 4 electrons in the outer level • reactivity varies among the elements • solids at room temperature
  21. 21. Group 15: Nitrogen group • group contains two nonmetals, two metalloids, and two metals • 5 electrons in the outer level • reactivity varies among the elements • solids at room temperature (except for nitrogen, which is a gas)
  22. 22. Group 16: Oxygen group • Group contains 3 nonmetals, one metalloid and one metal. • Atoms have 6 electron in their outermost energy level. • Are reactive, need only 2 electrons to fill outermost energy level. • All are solids at room temperature except oxygen.
  23. 23. Group 17: Halogens • Group contains only nonmetals. • Atoms have 7 electrons in their outermost energy level • Because it is quite easy to gain one electron halogens are very reactive. • Poor conductors of electricity, will react violently with alkali metals to form salts. • Chlorine and iodine are used as disinfectants, chlorine is used to treat water and iodine solution is used to disinfect wounds.
  24. 24. Group 18: Noble gases • Are all nonmetals. • Have full outermost energy level, making them very stable (unreactive). • They are colorless, odorless gases at room temperature. • Due to is unreactive nature, argon is used in lightbulbs so that it does not react with the glowing filament, unlike air. • Helium has a low density and because of its unreactive nature it can be used in balloons. • Helium, Neon, argon and xenon produce Yellow, orange-red, lavander and blue colors in “Neon”lights.
  25. 25. Hydrogen • Is so unique, cannot be grouped with any of the 18 groups. • Very reactive. • Colorless, odorless gas at room temperature, has a very low density. • Reacts explosively with oxygen so is used as a fuel in rockets. • Is the most abundant element in the universe.