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Chapter 6

Chapter 6. The Periodic Table and Groups of Elements. Development of the Periodic Table. Identifying Elements. Elements are identified from their line spectra. Atomic Spectroscopy -. Scientist. J.W. Dobereiner - (1780-1849).

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Chapter 6

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  1. Chapter 6 The Periodic Table and Groups of Elements

  2. Development of the Periodic Table • Identifying Elements Elements are identified from their line spectra Atomic Spectroscopy - • Scientist J.W. Dobereiner - (1780-1849) Several elements could be classified into groups of three, called triads, which have similar chemical properties Triads: (Li, Na, K), (Ca, Ba, Sr), (Cl, Br, I) J.A.R Newlands - (1837-1898) A pattern repeats every eight elements, called the pattern of octaves

  3. Dmitri Mendeleev - (1834-1907) Figure 5-4 Published the first periodic table Put elements with similar properties in the same group/family (column), organized the elements by atomic mass Lothar Meyer – (1830-1895) Produced an almost identical scheme for classifying elements as Mendeleev H.G.J. Moseley – (1887-1915) Developed concept of atomic numbers; periodic table should be arranged by atomic numbers, not atomic mass Periodic Law - When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern

  4. Reading the Periodic Table • Organizing the Squares Facts: 112 squares (elements) Row (across) = period (total 7 periods) Columns (down) = group/family (18 labeled groups) • Labeling and Naming 3 numbering systems for groups 1. European – Groups on left IA – VIIIA, IB – VIIIB *2. United States – longer groups on left and right are IA – VIIIA, and the middle is IB – VIIIB. Roman numerals were changed to Arabic numbers (1, 2, 3, . . .) 3. IUPAC – International Union of Pure and Applied Chemistry – numbered 1-18, but not widely adopted

  5. 1 2 Valence e- - outermost electrons +1 +2 Formal Charge 3 4 5 6 7 8 1A 2A Group # Metal Solid C +3 +4 -3 -2 -1 0 Alkali Metals 1 2 3 4 5 6 7 3A 4A 5A 6A 7A 8A Liquid Semimetal Br Alkaline Earth Metals Carbon Group Boron Group Oxygen Group Nitrogen Group Halogens Noble Gases Varies Gas Nonmetal H All Cations 3B 4B 5B 6B 7B 8B 1B 2B 3 4 5 6 Transition Metals 4 5 Inner Transition Metals

  6. Periodic Trends Half of the distance between two nuclei • Atomic Radii - Atomic radii decreases going across decrease Why: More e- on same energy level means more pull towards the nucleus Atomic radii increases going down Why: More energy levels means e- are getting further away from the nucleus increases Q: What would have a larger atomic radius, Cl or Se? A: Se

  7. ATOMIC RADIOUS

  8. Ionic Size - the size of an ion after it has gained or lost an electron Ionic size decreases going across from 5A to 7A increases decrease Why? groups 5A, 6A, and 7A all gain e- and because they are in the same energy level the increase in e- attracts the orbital closer to the nucleus Ionic size increases going across from 4A to 1A increases Why? groups 4A, 3A, 2A, 1A all give e- and because they are in the same energy level the decrease in e- creates less attraction to the nucleus Ionic size increases going down Why? As energy levels increase so do orbitals and therefore the distance from the nucleus to the valence e- Q: Which has the larger ionic radii, I or Na? A: I Group 8A does not undergo ionization

  9. the energy required to remove one electron from an neutral atom in a gaseous state • Ionization Energy - Li  Li+ + e- ionization energy = 8.64 x 10-19 J/atom Ionization energy increases going across increases Why? As you move across atoms prefer to gain e- rather than give them away so the amount of energy needed to give them away increases decreases Ionization energy decreases going down Why? As you move down the # of orbitals increases which means the valence e- are getting further away from the nucleus, therefore the nucleus is unable to hold on to them which make those e- easier to lose Q: Which has a higher ionization energy, Ba or S? A: S Opposite trend of atomic radii!

  10. Electron Affinity - the measure of an atom’s attraction for an extra electron F + e- F-electron affinity = -328 kJ/mol ** the more negative the better ** increases Electron affinity increases going across Why? As you move across atoms prefer to gain e- rather than give them away so their want/affinity for e- increases decreases Electron affinity decreases going down Why? As you move down the # of orbitals increases which means the valence e- are getting further away from the nucleus, therefore the nucleus doesn’t want/have the affinity to gain more e- because it can hardly keep the e- it has Q: Which has a higher electron affinity, K or F? A: F

  11. Electronegativity - Reflects an atoms ability to attract electrons in a chemical bond ** There are no units for electronegativity ** increases Electronegativity is on a scale of 0.0 to 4.0 Electronegativity increases going across decreases Why? As you move across atoms prefer to gain e- rather than give them away so their ability to attract more e- increases increases Electronegativity decreases going down Why? As you move down the # of orbitals increases which means the valence e- are getting further away from the nucleus, therefore the nucleus doesn’t want/have the affinity to gain more e- because it can hardly keep the e- it has Q: What element is the most electronegative? Which is the least? A: F (most – 4.0), Fr (least 0.7)

  12. Properties of Elements • luster/shine - malleable • good conductors (heat and electricity) - ductile • typically solids @ room temp (273K) Metal: • no luster/shine - not malleable • not good conductors - not ductile • typically gases @ room temp (273K) - color or colorless • a few solids (C, P, S, Se, I) - soft or hard • one (1) liquid Br, - Brittle Nonmetal: • metal/nonmetal properties (Semiconductors) Semimetal/Metalloids:

  13. S-Block S • Group 1A - Alkali Metals ashes Meaning: Li, Na, K, Rb, Cs, Fr Metals/Solids: H Nonmetal/Gas: Properties: • - low density • soft • low melting point • intense reaction with air and water (rapid tarnishing) • - one (1) valence e- in s-orbital • - forms 1+ charge • low ionization energy Sources & Uses: Sodium (7%) and potassium (8%) most abundant in earth’s crust Produced commercially NaCl (table salt), NaOCl (bleach), NaHCO3 (baking soda), NaOH (lye), LiCO3 (antidepressant)

  14. S-Block • Group 1A - Hydrogen Sources & Uses : Coal, petroleum, plants, animals; used to produce methanol for gasoline Properties : • nonmetal, gas • 1 valence e- • - forms 1+ charge • Hydrogen is colorless, odorless, and not very abundant in atmosphere, mostly found in water (H2O) • The metals are highly reactive • Soft, low density, low melting point and boiling point • React with Oxygen and water. Form +1 cations Na+ Sodium Cation

  15. S-Block • Group 2A - Alkaline Earth Metals - Form Cation 2+ Mg2+ Magnesium Cation Similar to alkali metals, unchanged by fire Meaning: Be, Mg, Ca, Sr, Ba, Ra Metal: • - two (2) valence e- • - forms 2+ charge • higher ionization energy Properties: • higher density (low) • higher melting point (low) • mild reactivity with H2O Sources & Uses: most abundant is Ca (5%) and Mg (6%) in earth’s crust compounds in nature CaCO3 (limestone), MgCO3 (magnesite), alloys produced commercially (Mg-Al, Mg-Zn), antacid Mg(OH)2

  16. D-Block D • Group 3B-2B - Transition Metals Sources & Uses : Important role in living organisms, valuable structure use, fireworks, photography, coins, jewelry, very abundant Cu + Sn = Bronze, Cu + Zn = Brass, Steel (Fe, Co, Ni, . .) Au + Ag = Yellow Gold, Au + Ni = White Gold Pure gold is 24 karats, 18k = (18/24) x 100% = 75% Au Metals/Alloys: Properties: • high density • high melting point • electrical conductors • hard or soft • - various # valence e- • - various charges • malleable (able to be hammered) • Ductile (able to be pull )

  17. P-Block P • Group 3A - Boron Group Sources & Uses : Alloyed for construction, found in an ore called bauxite Al, Ga, In, Tl; most abundant/important Al Metals: B Semimetal: - 3 valence e- - forms 3+ charge Properties of Al: • low density • strong when alloyed • not corrosive (Al2O3) - For cations 3+ Al3+ Aluminum Cation

  18. P-Block • Group 4A - Carbon Group Sources & Uses : Main component of fossil fuels, found in all living organisms; graphite, diamonds, sand, glass Sn, Pb Metals/Solids: Si, Ge Semimetal: Nonmetal: C - Form Cation and Anion +4, -4 C4- Carbide Anion Pb4+ Lead Cation Properties: - 4 valence e- - forms 4+ charge

  19. P-Block • Group 5A - Nitrogen Group Sources & Uses : N is 80% of earth’s atmosphere, couldn’t grow food without it (NH3); bones, H3PO4 for fertilizer Bi Metals: As, Sb Semimetal: Nonmetal: N, P • Form 3- anions • N-3 Nitride Properties : - 5 valence e- - forms 3- charge

  20. P-Block • Group 6A - Oxygen Group or CHALOGENS Sources & Uses : O is most abundant on earth, O2 to breath, O3 ozone; S (brimestone), FeS2 (fools gold), H2SO4 - Form anion 2- O2-oxide anion Po Metals: Te Semimetal: Nonmetal: O, S, Se Properties : - 6 valence e- - forms 2- charge - O: colorless, odorless, tasteless - S: bad odor

  21. P-Block • Group 7A - Halogens Meaning : Salt former Sources & Uses : CFC’s, NaCl, PVC, fire retardants, pesticides, antiseptic • forms 1- anions • Cl- Chlorine anion Semimetal: At Nonmetal: F (pale yellow), Cl (green-yellow), Br (dark red-brown), I (dark gray-violet) Properties : - 7 valence e- - forms 1- charge - diatomic molecules (F2, Cl2, Br2, I2)

  22. P-Block • Group 8A - Noble Gases Meaning : A tendency to remain apart; nobility Sources & Uses : Coolant, light bulbs, inert atmosphere, red light Nonmetal: He, Ne, Ar,Kr, Xe, Rn Properties : - 8 valence e- - forms 0 charge - least reactive

  23. F-Block • Inner Transition Metals 4f – Lanthanides, 5f – Actinides F 1st element in period (La, Ac) Meaning: Conflict: to begin with La, Ac or Ce, Th; e- configuration - various # valence e- - forms 3+ charge Properties: • silvery metals • soft • less reactive than Grp 2A, but too reactive to build • 5f element are radioactive; after U artificially made Sources & Uses: Occur in nature but hard to separate, commercial use in special steel alloy; fuel for nuclear power plants

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