History of The Periodic Table

Transcription

1 History of The Periodic Table

2 Organizing the Elements Chemists used the properties of elements to sort them into groups. JW. Dobreiner grouped elements into triads. A triad is a set of three elements with similar properties.

3 Mendeleev s Periodic Table In 1869, a Russian chemist and teacher published a table of the elements. Mendeleev arranged the elements in the periodic table in order of increasing atomic weight.

4 Henry Moseley 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

5 The periodic table is made up of rows and columns of elements.

6 A row is called a period A column is called a group or a family Across the rows (period), the elements have a feature that changes regularly Down the column (group), the elements are exactly the same in some way

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8 How difficult do you think it was to organize all the elements into the periodic table?

9 The Periodic Law In the modern periodic table elements are arranged in order of increasing atomic number. Periodic Law states: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

10 Groups/Families Columns of elements are called groups or families. Elements in each group have similar but not identical properties. For example, lithium (Li), sodium (Na), potassium (K), and other members of group IA are all soft, white, shiny metals. All elements in a group have the same number of valence electrons.

11 Elements in each group have similar but not identical properties

12 Elements are placed in columns by similar properties.

13 Alkali Metals Group 1 ALL elements in Group 1 have 1 electron in their outer shell They are shiny, have the consistency of clay, and are easily cut with a knife

14 Alkali Metals They are the most reactive metals. They react violently with water. Alkali metals are never found as free elements in nature. They are always bonded with another element.

15 Alkali Earth Metals Group 2 ALL elements in Group 2 have 2 electrons in their outer shell

16 Alkaline Earth Metals They are never found uncombined in nature.

17 Boron Family Group 13 ALL elements in Group 13 have 3 electrons in their outer shell

18 Carbon Family Group 14 ALL elements in Group 14 have 4 electrons in their outer shell

19 Group 15 Nitrogen Family ALL elements in Group 15 have 5 electrons in their outer shell

20 Oxygen Family Group 16 ALL elements in Group 16 have 6 electrons in their outer shell

21 Group 17 Halogens ALL elements in Group 17 have 7 electrons in their outer shell

22 Group 18 Noble Gases ALL elements in Group 18 have 8 electrons in their outer shell

23 Write a 3 sentence summary of how the groups on the periodic table are organized

24 Periods Each horizontal row of elements is called a period. The elements in a period are not alike in properties. properties change greatly across even given row.

25 The elements in a period are not alike in properties The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.

26 Period 1 Each element has space for one shell of electrons

27 Period 2 Each element in this period has two shells of electrons

28 Period 3 Each element in this period has 3 shells for electrons

29 Period 4 Each element in this period has 4 shells for electrons

30 Period 5 Each element in this period has 5 shells for electrons

31 Period 6 Each element in this period has 6 shells for electrons The Lanthanides are part of period 6

32 Period 7 Each element in this period has 7 shells for electrons The Actinides are part of period 7

33 Practice

34 Elements are grouped into three broad classes based on their general properties. 1. Metals 2. Nonmetals 3. Metalloids.

35 METALS Non-METALS METALLOIDS

36 Properties of Metals Metals are: good conductors of heat and electricity Shiny ductile (can be stretched into thin wires) malleable (can be pounded into thin sheets) Solid at room temperature except Hg React with acids

37 METALS

38 Properties of Non-Metals Non-metals are poor conductors of heat and electricity not ductile or malleable brittle and break easily dull Sulfur Many non-metals are gases.

39 Non-METALS

40 Properties of Metalloids have properties of both metals and non-metals. can be shiny or dull. conduct heat and electricity better than non-metals but not as well as metals. ductile and malleable. Silicon

41 METALLOIDS

42 Transition Elements (Transition Metals)

43 Transition Metals copper, tin, zinc, iron, nickel, gold, and silver. good conductors of heat and electricity.

44 Transition Metals The compounds are brightly colored used to color paints have 1 or 2 valence electrons Some transition elements can lose electrons in their next-to-outermost level.

45 inner transition metals: lanthanides and actinides are members of group 2 or 3. lanthanides actinides

46 Properties of lanthanides High melting points and boiling points. Very reactive. Burn easily in air. Belong to period 6

47 Properties of actinides All are radioactive. The metals tarnish readily in air. Belong to period 7 Elements above 92 do not exist in nature but have been manufactured in the lab

48 Hydrogen The hydrogen square sits atop group A1, but it is not a member of that group. Hydrogen is in a class of its own. It s a gas at room temperature. It has one proton and one electron. Hydrogen only needs 2 electrons to fill up its valence shell.

49 METAL, NON METAL OR METALLOID?

50 Trends in the periodic table: Atomic Radius Ionization Energy Electronegativity Reactivity

51 Atomic Radius The atomic radius is defined as one-half of the distance between two bonded nuclei.

52 Atomic Radius Trend Group Trend As you go down a column, atomic radius increases. Periodic Trend As you go across a period (L to R), atomic radius decreases.

53 atomic radius increases Atomic Radius atomic radius decreases

54 Ionization Energy The ionization energy is the energy required to remove an electron from an atom or ion.

55 Ionization Energy Trend Ionization Energy Decreases as You Move Down a Group Ionization energy tends to increase as you move from left to right across a period.

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57 Electronegativity Not all atoms in a compound share electrons equally. Knowing how strongly each atom attracts bonding electrons can help explain the physical and chemical properties of a compound Linus Pauling, an American chemist, made a scale of numerical values that reflect how much an atom in a molecule attracts electrons, called electronegativity values

58 Electronegativity Electronegativity is the measure of the ability of an atom in a chemical compound to attract electrons. The atom with the higher electronegativity will pull on the electrons more strongly than the other atom will

59 Electronegativity Trend Electronegativity Decreases as You Move Down a Group Electronegativity tends to increase as you move from left to right across a period.

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61 TRENDS ATOMIC RADIUS AND IONIZATION ENERGY

62 Reactivity Trends Different for metals and non metals Elements will be reactive depending on how many electron shells they have and how low their ionization energy is.

63 Reactivity Trend For Metals The reactivity of the metals in the 1 st and 2 nd group increases from the top to the bottom. The reactivity of the metals decreases from the left to the right.

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65 Reactivity trend for Non Metals The reactivity of the non metals in the 6 th and 7 th group decreases from the top to the bottom. The reactivity of the non metals decreases from the right to the left.

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67 What does this mean? Iron is more reactive than Nickel, so it will react with Nickel Iron is less reactive than Potassium, so it won t react with Potassium

68 REACTIVITY OF METALS

69 COMPLETE WORKSHEET