CHAPTER 5 THE PERIODIC TABLE Periodic table

The history and development of periodic table

1. THE PERIODIC TABLE Au Ag Hg Pb Ga CHAPTER 4

2. The Periodic Table: History During the nineteenth century, chemists began to categorize the elements according to similarities in their physical and chemical properties. The end result of these studies was our modern periodic table.

3. The Periodic Table: History Johann Dobereiner 1780 - 1849 In 1829, he classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical properties and orderly physical properties. Model of Triads (ex. Cl, Br, I and Ca, Sr, Ba) Middle Element Chemical Similarity Atomic Mass Relationships

4. The Periodic Table: History John Newlands 1838 - 1898 Law of Octaves In 1863, he suggested that elements be arranged in “octaves” because he noticed (after arranging the elements in order of increasing atomic mass) that certain properties repeated every 8th element

5. The Periodic Table: History

6. The Periodic Table: History Dmitri Mendeleev 1834 - 1907 In 1869 he published a table of the elements organized by increasing atomic mass.

7. The Periodic Table: History Lothar Meyer 1830 - 1895 At the same time, he published his own table of the elements organized by increasing atomic mass.

8. The Periodic Table: History

9. The Periodic Table: History

10. The Periodic Table: History Both Mendeleev and Meyer arranged the elements in order of increasing atomic mass. Both left vacant spaces where unknown elements should fit. So why is Mendeleev called the “father of the modern periodic table” and not Meyer, or both?

11. The Periodic Table: History Mendeleev s tated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U) was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown.

12. The Periodic Table: History In the specific cases of beryllium, indium, and uranium: Beryllium : Mendeleev recognized that beryllium's atomic mass (around 9) didn't match its chemical behavior, which was more akin to other elements in the alkaline earth metals. He adjusted its atomic mass upward to approximately 9.4 to better align it with its chemical properties. Indium : Indium's atomic mass was initially known to be around 75, but Mendeleev adjusted it to approximately 114, which better placed it in the periodic table and accounted for its chemical behavior. Uranium : Mendeleev initially placed uranium with an atomic mass of approximately 120. However, as he worked on the periodic table, he recognized that uranium didn't fit well in that position, and he adjusted its atomic mass downward to around 240. This adjustment allowed uranium to be grouped with other elements exhibiting similar properties.

13. The Periodic Table: History After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleev’s predictions for Sc, Ga, and Ge were amazingly close to the actual values, his table was generally accepted.

14. The Periodic Table: History

15. The Periodic Table: History However, in spite of Mendeleev’s great achievement, problems arose when new elements were discovered and more accurate atomic weights determined. By looking at our modern periodic table, can you identify what problems might have caused chemists a headache? Ar and K Co and Ni Te and I Th and Pa

16. The Periodic Table: History Henry Moseley 1887 - 1915 In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. He rearranged the elements in order of increasing atomic number. *“There is in the atom a fundamental quantity which increases by regular steps as we pass from each element to the next. This quantity can only be the charge on the central positive nucleus”

17. The Periodic Table: History Henry Moseley His research was halted when the British government sent him to serve as a foot soldier in WWI. He was killed in the fighting in Gallipoli by a sniper’s bullet, at the age of 28. Because of this loss, the British government later restricted its scientists to noncombatant duties during WWII.

18. The Periodic Table: History Glenn T. Seaborg After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became known as the Actinide series. 1912 - 1999

19. The Periodic Table: History Glenn T. Seaborg He is the only person to have an element named after him while still alive. 1912 - 1999 "This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize."

20. The Periodic Table: History Glenn T. Seaborg He is the only person to have an element named after him while still alive. 1912 - 1999 "This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize."

21. The Periodic Table: History Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.

22. The Periodic Table: Periodic Table Geography The horizontal rows of the periodic table are called PERIODS. The vertical columns of the periodic table are called GROUPS, or FAMILIES.(The elements in any group of the periodic table have similar physical and chemical properties! )

23. Metals, Nonmetals, and Metalloids

24. Metals Most elements are metals. The 88 elements to the left of the stair step line are metals or metal- like elements except Hydrogen . Examples of metals:

25. Physical Properties A physical property is a characteristic you can observe or measure For example, a physical property of some metals are that they are shiny.

26. Physical Properties of Metals Good conductors of heat and electricity. Luster: shiny Ductile (can be stretched into thin wires) Malleable (can be pounded into thin sheets)

27. Properties of Metal, Cont. Usually solids at room temperature High melting points and boiling points (except Hg - Mercury) High densities and reflect light

28. Chemical Properties of Metals A chemical property of metals is that it Corrodes easily Gradual wearing away Ex: Silver tarnishing or iron rusting

29. What are Chemical Properties? A chemical property may only be observed by chemical reaction. This property measures the potential for undergoing a chemical change. A chemical reaction is the process by which one or more substances change to produce one or more different substances.

30. Metalloids The periodic table contains a stair- step line, these elements along that line are called metalloids. The “- oid” ending means – like or similar to Elements in this group have properties of both metals and non- metals.

31. Physical Properties of Metalloids Solids that can be shiny or dull. They can conduct heat and have electrical charges,but not as well as metals . They are ductile and malleable. Silicon

32. Non-Metals Nonmetals are found on the right side of the periodic table. Their characteristics are opposite those of metals.

33. Physical Properties of Non-Metals poor conductors of heat and electricity. Non- metals are not ductile or malleable. Solid non- metals are brittle and break easily. Dull, no shiny luster, don’t reflect light. Many non- metals are gases . Silicon

34. Malleable Matter that can be pounded or rolled into thin sheets without shattering.

35. Brittle Matter that shatters and breaks into pieces when pounded

36. Conductor Allows heat or electrical charge can pass through material Does metal have good conductivity? Give me an example!

37. Insulator Does not allow electricity to pass through easily – Known as a poor conductor, what in this picture would you consider to be the insulator?

38. Luster The way matter reflects light from its surface Matter that reflects a large amount of light is called SHINY (write: high light=shiny) Matter that reflects little light from its surface is called DULL. (write: low light=dull)

39. Ductile – ability to be stretched into a wire

40. One of the really cool things about electron configurations is their relationship to the periodic table. Basically the periodic table was constructed so that elements with similar electron configurations would be aligned into the same groups (columns). T HE PERIODIC TABLE: Periodic Properties Periodic Table showing last orbital filled for each element

41. The periodic table shown above demonstrates how the configuration of each element was aligned so that the last orbital filled is the same except for the shell. The reason this was done is that the configuration of an element gives the element its properties and similar configurations yield similar properties T HE PERIODIC TABLE: Periodic Properties Periodic Table showing last orbital filled for each element

42. ATOMIC SIZE The size of atoms increases going down in the periodic table . This should be intuitive since with each row of the table you are adding a shell (n). What is not as intuitive is why the size decreases from left to right. But again, the construction of the electron configuration gives us the answer. What are you doing as you go across the periodic table? Answer , adding protons to the nucleus and adding electrons to the valence shell of the element. What is not changing as you cross a period? Answer, the inner shell electrons. T HE PERIODIC TABLE: Periodic Properties

43. ELECTRONEGATIVITY Electronegativity is an atoms ability to pull electrons towards itself. The electronegativity values increase from left to right and bottom to top in the periodic table excluding the Noble gases. The most electronegative element is Fluorine. From these electronegativity values we can derive the patterns of two other periodic properties: Ionization Energy and Electron Affinity. T HE PERIODIC TABLE: Periodic Properties

44. T HE PERIODIC TABLE: Periodic Properties IONIZATION ENERGY Ionization energy is the amount of energy required to remove an electron from an atom. All ionization energies are positive values because all of these removals (even those for elements that form positive ions) require input of energy. The more electronegative the element, the higher the ionization energy.

45. T HE PERIODIC TABLE: Periodic Properties ELECTRON AFFINITY The Electron Affinity of an element is the amount of energy gained or released with the addition of an electron. The electronegativity and Electron Affinity increase in the same pattern in the periodic table. Left to right and bottom to top.