Organizing the elements

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1 THE PERIODIC TABLE

2 Organizing the elements In nature and in the lab we have discovered over 100 different elements. We ve organized the elements into a table based on their PHYSICAL and CHEMICAL PROPERTIES It took us almost 2000 years to figure out the properties of the elements currently in the Periodic Table of Elements and arrange them.

3 I. Developing the Periodic Table In the early 1800s, enough information was known about the elements that scientists wanted an easy way to categorize the Earth s ingredients.

4 So why don t we just list the elements in a straight line? Why make a table? An analogy: When you go to the grocery store and are looking for a specific ingredient, you want things to be grouped in a logical way so that you can easily find what you need. Scientists wanted the elements that they were using in their experiments to also be grouped so that they could easily find elements with the characteristics that they desired.

5 Developing the Periodic Table Many methods of organization were tried before scientists found the most effective way of grouping the elements

6 Mayan Periodic Table

7 The Who s Who of Periodic Table Development (You need to know Mendeleev and Mosely.)

8 Dmitri Mendeleev In 1869 he published a table of the elements organized by increasing atomic mass

9 Developing the Periodic Table Mendeleev stated that the properties of elements are a periodic function of their atomic masses. If we lay out all of the elements in order by atomic mass, we would see the same properties showing up periodically For example, as you would begin down the list of the first 18 elements, every 9 th (or so) atom would be super reactive and want to gain 1 electron

10 Lothar Meyer At the same time, he published his own table of the elements organized by increasing atomic mass

11 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? Father of the Modern Periodic Table

Mendeleev used his periodic function theory and corrected the atomic

was so confident in his table that he used it to predict the physical

After the discovery of these unknown elements between 1874 and 1885,

12 Mendeleev used his periodic function theory and 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 (Sc, Ga & Ge). After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleev s predictions were amazingly close to the actual values, his table was generally accepted.

13 Mendeleev s Periodic Table

Mendeleev s Periodic Table However, in spite of Mendeleev s great achievement, problems arose when new elements were discovered and more accurate atomic weights determined.

14 Mendeleev s Periodic Table 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, we can identify some problems which might have caused chemists a headache. Atomic Masses Ar and K (40-39) Co and Ni (59-58) Te and I ( ) Th and Pa ( )

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.

15 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. *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. 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

16 Periodic Law This arrangement allowed elements with similar properties to be lined up into the same column in the periodic table Ex. All of the elements in group 1 are extremely reactive when by themselves and want to give away 1 electron

17 QOD Mendeleev published a table of the elements organized by increasing what? Atomic Mass Which scientist arranged elements on the periodic table according to atomic number? Henry Moseley

18 PERIODIC TABLE GEOGRAPHY Where are elements found?

19 The horizontal rows of the periodic table are called PERIODS.

20 The elements in any group of the periodic table have similar physical and chemical properties! The vertical columns of the periodic table are called GROUPS, or FAMILIES.

21 Organizing Information on the Periodic Table Highlight/darken the stair step line starting between B and Al. Label the left side: metals Label the right side: nonmetals Shade B, Si, Ge, As, Sb, Te, At and key as METALLOID.

23 General Properties of Metals Metals are good conductors of heat and electricity Metals are malleable oeasily bent and shaped Metals are ductile oable to be drawn out into a wire Metals have a shiny luster

24 Examples of Metals Copper, Cu, is a relatively soft metal, and a very good electrical conductor. Zinc, Zn, is more stable than potassium Mercury, Hg, is the only metal that exists as a liquid at room temperature

General Properties of Metalloids They have

Metalloids are more brittle than metals,

25 General Properties of Metalloids They have properties of both metals and nonmetals. Metalloids are more brittle than metals, less brittle than most nonmetallic solids Metalloids are semiconductors of electricity Some metalloids possess metallic luster Ex: Silicon possesses a metallic luster, yet it is an inefficient conductor and is brittle.

26 General Properties of Nonmetals Nonmetals are poor conductors of heat and electricity Good insulators Nonmetals tend to be brittle when solids Many nonmetals are gases at room temperature Carbon, the graphite in pencil lead is a great example of a nonmetallic element.

Examples of Nonmetals Sulfur, S, was once

27 Examples of Nonmetals Sulfur, S, was once known as brimstone Microspheres of phosphorus, P, a reactive nonmetal Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure

28 1 1A 18 8A 1 1 H 2 2A 13 3A 14 4A 15 5A 16 6A 17 7A 2 He 2 3 Li 4 Be 5 B 6 C 7 N 8 O 9 F 10 Ne 3 11 Na 12 Mg Al 14 Si 15 P 16 S 17 Cl 18 Ar 4 19 K 20 Ca 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn 31 Ga 32 Ge 33 As 34 Se 35 Br 36 Kr 5 37 Rb 38 Sr 39 Y 40 Zr 41 Nb 42 Mo 43 Tc 44 Ru 45 Rh 46 Pd 47 Ag 48 Cd 49 In 50 Sn 51 Sb 52 Te 53 I 54 Xe 6 55 Cs 56 Ba 72 Hf 73 Ta 74 W 75 Re 76 Os 77 Ir 78 Pt 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 Rn 7 87 Fr 88 Ra 104 Rf 105 Db 106 Sg 107 Bh 10 8 Hs 109 Mt 110 Uun 111 Uuu 112 Uub 57 La 58 Ce 59 Pr 60 Nd 61 Pm 62 Sm 63 Eu 64 Gd 65 Tb 66 Dy 67 Ho 68 Er 69 Tm 70 Yb 71 Lu 89 Ac 90 Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf 99 Es 100 Fm 101 Md 102 No 103 Lr The Periodic Table of Elements P E R I O D Alkali Metals Alkali Earth Metals Transition Metals Chalcogens Halogens Noble Gases Lanthanides Actinides M E T A L LO I D Transition Metals Transition Metals Transition Metals Write the group names!

29 Alkali Metals

30 Alkaline Earth Metals

31 Transition Metals

32 These elements are also called the rare-earth elements. Notice that it continues from period 6 & 7 InnerTransition Metals

33 Halogens

34 Noble Gases Last slide

35 QOD More than twothirds of the elements on the periodic table are what? If solid, non metals tend to be what? Good insulators Metals

36 III. Periodic Law Before we can discuss the characteristics of each group, we must introduce the Period Law.

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

38 Periodic Table Review Elements with similar e- configurations are placed in the same group. (same number of e - in last energy level) The number of electrons in the outermost energy level determines how reactive an element will be These electrons in the highest energy level are called Valence Electrons Therefore elements in the same group have the same number of valence e -

40 Group 1 EX: H = 1s 1 Li = 1s 2 2s 1 Na = 1s 2 2s 2 2p 6 3s 1 All elements in group 1 have 1 valence electron (1 electron in highest energy level)

41 Group 17 Ex: F = 1s 2 2s 2 2p 5 Cl = 1s 2 2s 2 2p 6 3s 2 3p 5 Br = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 All elements in group 17 have 7 valence electrons (7 electrons in highest energy level)

42 Valence Electrons Highlight the valence electrons on your periodic table

43 Octet Rule Octet Rule = Eight electrons in an outer level render an atom unreactive (stable). Therefore all atoms are trying to get to this state. Atoms obtain an octet of electrons in their valence orbital by taking electrons from another atom, giving their valence electrons away, or sharing electrons with another atom.

44 Octet Rule Whether an atom gains, loses or shares e- to form an octet depends on how close the atom is to having the 8 e-. If an atom has less than 4 valence e- then it will try to lose them so that the energy level below (which is full w/ an octet) will then be considered the outermost energy level. Ex: Na = 1s 2 2s 2 2p 6 3s 1 If Sodium loses 1 electron in the 3s energy level, then energy level 2 will be considered the outermost energy level. Since energy level 2 has an octet the atom will be stable.

45 Octet Rule If an atom has more than 4 valence electrons it will try to steal electrons from other atoms to form an octet Ex: Cl = 1s 2 2s 2 2p 6 3s 2 3p 5 If Chlorine gains 1 electron it will have an octet and be stable.

46 Octet Rule Atoms with 4 electrons in their valence shell will share 4 electrons with other atoms to feel as though they have an octet.

47 QOD The element found in Group 14 and in Period 2 is? Carbon The number of valence electrons in an atom with an electron configuration of 1s 2 2s 2 2p 6 3s 2 3p 3 is? 5

48 IV. Oxidation Numbers Our knowledge of e- configurations and the stability of noble gases allows us to predict oxidation numbers for elements. Oxidation numbers represent the charge an ion obtains after losing or gaining valence electrons. Ex. Ca = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 2 valence e-, will want to get rid of them so that the full 3 rd energy level (8 electrons) will then be it s outermost shell Ca 2+ =1s 2 2s 2 2p 6 3s 2 3p 6

49 Oxidation Numbers Ex. Ca = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Ca 2+ =1s 2 2s 2 2p 6 3s 2 3p 6 *** Octet Rule: atoms want to have a full highest energy level (8 electrons) ** If an atom has less than 4 valence electrons they will lose their valence electrons so that the full energy level below will then be considered the outermost shell, and become a positive ion (cation)

50 Oxidation Numbers Ex. F = 1s 2 2s 2 2p 5 F - = 1s 2 2s 2 2p 6 *** Octet Rule: atoms want to have a full highest energy level (8 electrons) ** If an atom has more than 4 valence electrons they will gain (steal) electrons until they have 8 electrons (full energy level octet), and become a negative ion (anion)

51 Oxidation Numbers *on your periodic table, write in the oxidation number of each group Tend to have more than one oxidation number or 4+

52 QOD What is the element with the electron configuration of: 1s 2 2s 2 2p 6 3s 2 How many valence electrons? What would be the oxidation number? Magnesium 2 valence e- Mg +2 What is the element with the electron configuration of: [Ar] 4s 2 3d 10 4p 3 How many valence electrons? What would be the oxidation number? Arsenic 5 valence e- As -3

53 V. Periodic Groups & Their Properties

get rid of it to be stable (octet in energy level below) NEVER found alone in nature are always

54 Alkali Metals Group 1 Metals Soft silver metals Less dense than other metals so melt and boil easily All alkali metals have 1 valence electron This makes them very reactive because they want to get rid of it to be stable (octet in energy level below) NEVER found alone in nature are always bonded to something else; they are too reactive Potassium, K reacts with water and must be stored in kerosene

55 Alkaline Earth Metals Group 2 Metals Shiny silvery - white All alkaline earth metals have 2 valence electrons This makes them very reactive because they want to get rid of it to be stable (octet in energy level below) Alkaline earth metals are less reactive than alkali metals Alkaline earth metals are not found pure in nature; they are too reactive Found in Earth s crust in mineral form.

56 Alkaline Earth Metals

unbonded in nature; they are too reactive Halogens in their pure form are diatomic molecules (F

57 Halogens Group 17 Nonmetals Halogens all have 7 valence electrons This makes them very reactive because they are SO CLOSE to having an octet, just need 1 more e- Halogens are never found unbonded in nature; they are too reactive Halogens in their pure form are diatomic molecules (F 2, Cl 2, Br 2, and I 2 ) Most important group to be used in industry Chlorine is a yellow-green poisonous gas

58 Chalogens Group 16 nonmetals Have 6 valence electrons Semi-reactive Diverse group that includes nonmetals, metalloids, and metals

59 Noble Gases Group 18 Nonmetals Noble gases have 8 valence electrons (except helium, which has only 2) This makes them extremely stable and unreactive because they have filled valence shells. They don t bond/react with other elements because they don t need to gain or lose e-) Noble gases are ONLY found alone in nature monatomic gasses Colorless, odorless; they were among the last of the natural elements to be discovered

60 Noble Gases

61 QOD Which elements have the most similar chemical properties Those in the same family or those in the same period Same Family Which of the groups on the periodic table are too reactive to be found as monoatomic atoms in nature? Alkaline metals & alkaline earth metals

62 VI. Periodic Trends

63 Using the Periodic Table to Predict Properties of Elements The basis of the periodic table is the atomic structure (number of protons, neutrons and electrons) of the elements. Position on the table and properties of these elements arise from the e- configurations of the atoms. Properties such as density, atomic radius, oxidation numbers, ionization energy, and e- affinity can be predicted.

64 A. Atomic Radius (size of atoms) As principal quantum number increases (you go down a group), the size of the electron cloud increases (more orbitals). Size of atoms increase moving down Per. Table.

65 Atomic Radius Atoms in the same period have the same quantum number; however, positive charge on the nucleus increases by one proton for each element in a period. This pulls the e- cloud in tighter, decreasing atomic radius.

66 Decreasing Atomic Size Across a Period Li Be B

67 Predicting Atomic Radius General rule: atomic size increases as you move diagonally from top right corner to bottom left corner.

68 B. Ionization Energy The energy required to remove an e- from an atom. Remove the most loosely held e- is first ionization energy. Measured in kilojoules per mole (kj/mol)

69 Ionization Energy As you move down the group, the ionization goes from high to low ionization energy. The larger the atom, the less energy is required because the e- are farther from the positive center.

70 Ionization Energy As you move from left to right across a period, the ionization goes from low to high ionization energy.

71 Classification based on First Ionization Energy METAL 1. Low 1 st ionization energy. 2. Located on left side of Periodic Table. 3. Form positive ions 4. Will give away their electrons. Ca = [Ar] 4s 2 2 valence e- positive ion: Ca +2 NONMETAL 1. High 1 st ionization energy. 2. Located on the right side of Periodic Table. 3. Form negative ions 4. Will NOT give away their electrons, they want to gain electrons. F = [He] 2s 2 2p 5 7 valence e- negative ion: F -

72 Multiple Ionization Energies Additional e- can be lost from an atom and the ionization energies can be measured. Notice that the energy increases greatly to remove more e- IONIZATION ENERGIES (kilojoules per mole) Element 1 st 2 nd 3 rd 4 th 5 th H He Li Be B

73 C. Ionization Energies It increases from left to right, bottom to top and bottom left to top right corners.

74 Video: Ionization Energy (1:52)

75 C. Electronegativity Electronegativity is the ability of an atom to capture an electron..

76 Electronegativity As you move from left to right across a period, the electronegativity increases because elements on the left side want to lose electrons to be like the nearest noble gas (octet rule) so do not want to grab electrons (low electronegativity) Elements on the right side want to gain electrons to be like the nearest noble gas, so the will grab electrons a lot. (high electronegativity)

77 Electronegativity THE EXCEPTION TO THIS RULE: NOBLE GASES They have no electronegativity at all because they are noble gases, and don t need any more electrons. (No electronegativity)

78 Electronegativity As you move from higher to lower in a group, the electronegativity decreases due to the shielding effect (which states that electrons in outer energy levels are held less tightly than those in lower energy levels). Generally, if an atom doesn t hold the electrons it has very much, it won t grab electrons from other atoms much, either.

79 C. Electronegativity It increases from left to right, bottom to top and bottom left to top right corners.

80 Review Based on our trends: The most reactive metal element would be Francium The most reactive nonmetal element would be Fluorine Last slide

81 In Summary Periodic table is a chart of elements in which the elements are arranged based on their e- configurations which dictates their properties. Moving down a group in the periodic table, atomic radii becomes larger because more energy levels are needed for more e-.

82 In Summary As the size becomes larger, the e- are located farther away from the positive center. This decreases the affinity of that atom to hold on to these outer e-, thus decreasing e- affinity. Ionization energy is low because it is easy for the atom to lose these outer e-.

83 In Summary Moving across a period in the periodic table, atomic radii becomes smaller because the energy levels of periods are the same but the positive centers of atoms increase. This pulls the e- cloud closer to the nucleus, making the atom smaller. Ionization energy increases for these smaller atoms.

84 THE END

Made the FIRST periodic table

Made the FIRST periodic table 1869 Mendeleev organized the periodic table based on the similar properties and relativities of certain elements Later, Henri Moseley organized the elements by increasing