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Chapter 14 “The Periodic Table” Pre-AP Chemistry Charles Page High School Stephen L. Cotton.

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Presentation on theme: "Chapter 14 “The Periodic Table” Pre-AP Chemistry Charles Page High School Stephen L. Cotton."— Presentation transcript:

1 Chapter 14 “The Periodic Table” Pre-AP Chemistry Charles Page High School Stephen L. Cotton

2 Section 14.1 Organizing the Elements u OBJECTIVES: Explain how elements are organized in a periodic table.

3 Section 14.1 Organizing the Elements u OBJECTIVES: Compare early and modern periodic tables.

4 Section 14.1 Organizing the Elements u OBJECTIVES: Identify three broad classes of elements.

5 Section 14.1 Organizing the Elements u By the year 1700, only about 13 elements had been identified u As more were discovered, we needed a way to organize the elements.

6 Section 14.1 Organizing the Elements u Chemists used the properties of elements to sort them into groups. u By the mid-1800s, about 70 elements were known to exist

7 Mendeleev’s Periodic Table u Dmitri Mendeleev – Russian chemist u Arranged elements in order of increasing atomic mass u Thus, the first “Periodic Table”

8 Mendeleev u Left blanks for undiscovered elements u Based on the blanks, new elements were discovered u 1894 found Argon, within 5 years found He, Ne, Kr, Xe, Rn

9 A better arrangement u In 1913, Henry Moseley – British physicist, arranged elements according to increasing atomic number Co & Ni; Ar & K; Te & I u The arrangement used today

10

11 Spiral Periodic Table Another possibility: Spiral Periodic Table

12 The Periodic Law says: u When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

13 The Periodic Law says: u Horizontal rows = periods There are 7 periods u Vertical column = group (or family) Similar physical & chemical properties Identified by number & letter

14 Areas of the periodic table u Three classes of elements are: 1) metals 2) nonmetals 3) metalloids (semi-metals)

15 Areas of the periodic table 1) Metals: electrical conductors, have luster, ductile, malleable 2) Nonmetals: generally brittle and nonlustrous, poor conductors of heat and electricity

16 Areas of the periodic table 3) Metalloids: border the line Properties are intermediate between metals and nonmetals

17 Section 14.1 Classifying the Elements u OBJECTIVES: Describe the information in a periodic table.

18 Section 14.1 Classifying the Elements u OBJECTIVES: Classify elements based on electron configuration.

19 Section 14.1 Classifying the Elements u OBJECTIVES: Distinguish representative elements and transition metals.

20 Electron Configurations in Groups u Elements can be sorted into different groupings based on their electron configurations

21 Groups of elements u Group 1A – alkali metals u Hydrogen is not part of this group

22 1s11s1 1s 2 2s 1 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4 f 14 5d 10 6p 6 7s 1 H 1 Li 3 Na 11 K 19 Rb 37 Cs 55 Fr 87 Do you notice any similarity in these configurations of the alkali metals?

23 Groups of elements u Group 2A – alkaline earth metals Do not dissolve well in water, hence “earth metals”

24 Group 1A are the alkali metals (not Hydrogen) Group 2A are the alkaline earth metals H

25 Groups of elements u Group 7A – halogens Means “salt-forming”

26 Electron Configurations in Groups 1) Noble gases are the elements in Group 8A u Electron configuration has the outer s and p sublevels completely full

27 He 2 Ne 10 Ar 18 Kr 36 Xe 54 Rn 86 1s21s2 1s 2 2s 2 2p 6 1s 2 2s 2 2p 6 3s 2 3p 6 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 Do you notice any similarity in the configurations of the noble gases?

28 u Group 8A are the noble gases u Group 7A is called the halogens

29 Electron Configurations in Groups 2) Representative Elements are in Groups 1A – 7A u Display wide range of properties, thus a good “representative” u Outer s and p electron configurations are NOT filled

30 1A 2A3A4A5A6A 7A 8A u Elements in the 1A-7A groups are called the representative elements outer s or p filling

31 Electron Configurations in Groups 3) Transition metals are in the B columns of the periodic table u s sublevel full, and is now filling the d sublevel

32 Electron Configurations in Groups 4) Inner Transition Metals are located below the main body of the table, in two horizontal rows u s sublevel full, and is now filling the f sublevel

33 Section 14.2 Periodic Trends u OBJECTIVES: Describe trends among the elements for atomic size.

34 Section 14.2 Periodic Trends u OBJECTIVES: Explain how ions form.

35 Section 14.2 Periodic Trends u OBJECTIVES: Describe periodic trends for first ionization energy, ionic size, and electronegativity.

36 Trends in Atomic Size u How do you measure the size of 1 atom? u The electron cloud doesn’t have a definite edge. u Measure the Atomic Radius - this is half the distance between the two nuclei of a diatomic molecule.

37 Atomic Size u Measure the Atomic Radius - this is half the distance between the two nuclei of a diatomic molecule. } Radius

38 Periodic Table Trends u Influenced by three factors: 1. Energy Level Higher energy level is further away. 2. Charge on nucleus (# protons) More charge pulls electrons in closer. u 3. Shielding effect (a blocking effect?)

39 What do they influence? u Energy levels and Shielding have an effect on the GROUP (  ) u Nuclear charge has an effect on a PERIOD (  )

40 #1. Atomic Size - Group trends u As we increase the atomic number (or go down a group)... u each atom has another energy level, u so the atoms get bigger. H Li Na K Rb

41 #1. Atomic Size - Period Trends u Going from left to right across a period, the size gets smaller. u Electrons are in the same energy level. u But, there is more nuclear charge. u Outermost electrons are pulled closer. NaMgAlSiPSClAr

42 Atomic Number Atomic Radius (pm) H Li Ne Ar 10 Na K Kr Rb 3 Period 2

43 Ions u Some compounds are composed of particles called “ions” u An ion is an atom (or group of atoms) that has a positive or negative charge

44 Ions u Atoms are neutral because the number of protons equals electrons u Ions are formed when atoms gain or lose electrons

45 Ions u Metals tend to LOSE electrons, from their outer energy level Sodium loses one: there are now more protons (11) than electrons (10), and thus a positively charged particle is formed = “cation” The charge is written as a number followed by a plus sign: Na 1+ Now named a “sodium ion”

46 Ions u Nonmetals tend to GAIN one or more electrons Chlorine will gain one electron Protons (17) no longer equals the electrons (18), so a charge of -1 Cl 1- is re-named a “chloride ion” Negative ions are called “anions”

47 #2. Trends in Ionization Energy u Ionization energy is the amount of energy required to completely remove an electron (from a gaseous atom). u Removing one electron makes a 1+ ion. u The energy required to remove only the first electron is called the first ionization energy.

48 Ionization Energy u The second ionization energy is the energy required to remove the second electron. Always greater than first IE. u The third IE is the energy required to remove a third electron. Greater than 1st or 2nd IE.

49 SymbolFirstSecond Third H He Li Be B C N O F Ne 1312 2731 520 900 800 1086 1402 1314 1681 2080 5247 7297 1757 2430 2352 2857 3391 3375 3963 11810 14840 3569 4619 4577 5301 6045 6276 Table 6.1, p. 173

50 SymbolFirstSecond Third H He Li Be B C N O F Ne 1312 2731 520 900 800 1086 1402 1314 1681 2080 5247 7297 1757 2430 2352 2857 3391 3375 3963 11810 14840 3569 4619 4577 5301 6045 6276 Why did these values increase so much ?

51 What factors determine IE u The greater the nuclear charge, the greater IE. u Greater distance from nucleus decreases IE u Filled and half-filled orbitals have lower energy, so achieving them is easier, lower IE. u Shielding effect

52 Shielding u The electron on the outermost energy level has to look through all the other energy levels to see the nucleus. u Second electron has same shielding, if it is in the same period

53 Ionization Energy - Group trends u As you go down a group, the first IE decreases because... The electron is further away from the attraction of the nucleus There is more shielding.

54 Ionization Energy - Period trends u All the atoms in the same period have the same energy level. u Same shielding. u But, increasing nuclear charge u So IE generally increases from left to right. u Exceptions at full and 1/2 full orbitals.

55 First Ionization energy Atomic number He u He has a greater IE than H. u Both elements have the same shielding since electrons are only in the first level u But He has a greater nuclear charge H

56 First Ionization energy Atomic number H He Li has lower IE than H more shielding further away l These outweigh the greater nuclear charge Li

57 First Ionization energy Atomic number H He Be has higher IE than Li same shielding l greater nuclear charge Li Be

58 First Ionization energy Atomic number H He B has lower IE than Be same shielding greater nuclear charge l By removing an electron we make s orbital half-filled Li Be B

59 First Ionization energy Atomic number H He Li Be B C

60 First Ionization energy Atomic number H He Li Be B C N

61 First Ionization energy Atomic number H He Li Be B C N O u Oxygen breaks the pattern, because removing an electron leaves it with a 1/2 filled p orbital

62 First Ionization energy Atomic number H He Li Be B C N O F

63 First Ionization energy Atomic number H He Li Be B C N O F Ne u Ne has a lower IE than He u Both are full, u Ne has more shielding u Greater distance

64 First Ionization energy Atomic number H He Li Be B C N O F Ne Na has a lower IE than Li Both are s 1 Na has more shielding l Greater distance Na

65 First Ionization energy Atomic number

66 Driving Forces u Full Energy Levels require lots of energy to remove their electrons. u Noble Gases have full orbitals. u Atoms behave in ways to try and achieve a noble gas configuration.

67 2nd Ionization Energy u For elements that reach a filled or half-filled orbital by removing 2 electrons, 2nd IE is lower than expected. u True for s 2 u Alkaline earth metals form 2+ ions.

68 3rd IE u Using the same logic s 2 p 1 atoms have an low 3rd IE. u Atoms in the aluminum family form 3+ ions. u 2nd IE and 3rd IE are always higher than 1st IE!!!

69 Trends in Ionic Size: Cations u Cations form by losing electrons. u Cations are smaller than the atom they came from – not only do they lose electrons, they lose an entire energy level. u Metals form cations. u Cations of representative elements have the noble gas configuration before them.

70 Ionic size: Anions u Anions form by gaining electrons. u Anions are bigger than the atom they came from – have the same energy level, but greater nuclear charge u Nonmetals form anions. u Anions of representative elements have the noble gas configuration after them.

71 Configuration of Ions u Ions always have noble gas configurations (a full outer level) u Na atom is: 1s 2 2s 2 2p 6 3s 1 u Forms a 1+ ion: 1s 2 2s 2 2p 6 u Same configuration as neon. u Metals form ions with the configuration of the noble gas before them - they lose electrons.

72 Configuration of Ions u Non-metals form ions by gaining electrons to achieve noble gas configuration. u They end up with the configuration of the noble gas after them.

73 Ion Group trends u Each step down a group is adding an energy level u Ions therefore get bigger as you go down, because of the additional energy level. Li 1+ Na 1+ K 1+ Rb 1+ Cs 1+

74 Ion Period Trends u Across the period from left to right, the nuclear charge increases - so they get smaller. u Notice the energy level changes between anions and cations. Li 1+ Be 2+ B 3+ C 4+ N 3- O 2- F 1-

75 Size of Isoelectronic ions u Iso- means the same u Iso electronic ions have the same # of electrons u Al 3+ Mg 2+ Na 1+ Ne F 1- O 2- and N 3- all have 10 electrons u all have the same configuration: 1s 2 2s 2 2p 6 (which is the noble gas neon)

76 Size of Isoelectronic ions? u Positive ions that have more protons would be smaller. Al 3+ Mg 2+ Na 1+ Ne F 1- O 2- N 3-

77 #3. Trends in Electronegativity u Electronegativity is the tendency for an atom to attract electrons to itself when it is chemically combined with another element. u They share the electron, but how equally do they share it? u An element with a big electronegativity means it pulls the electron towards itself strongly!

78 Electronegativity Group Trend u The further down a group, the farther the electron is away from the nucleus, plus the more electrons an atom has. u Thus, more willing to share. u Low electronegativity.

79 Electronegativity Period Trend u Metals are at the left of the table. u They let their electrons go easily u Thus, low electronegativity u At the right end are the nonmetals. u They want more electrons. u Try to take them away from others u High electronegativity.

80 The arrows indicate the trend: Ionization energy and Electronegativity INCREASE in these directions

81 Atomic size and Ionic size increase in these directions:

82 Summary Chart of the trends: Figure 6.22, p.178


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