The Representative Elements

1
The Representative Elements

• Representative elements
• chemical properties are determined by the valence
  s and p electrons
• include elements in group IA through VIIIA
• Diagonal line divides the metals from the
  nonmetals
• 8 metalloids exhibit both metallic and
  nonmetallic properties

2
The Representative Elements

• Metals vs. Nonmetals
• Metals tend to lose valence electrons to form
  cations
• Nonmetals tend to gain valence electrons to form
  anions
• Metallic character increases going down a group
  (I.E. Decreases going down a group)

3
The Representative Elements

• Size and Group Anomalies
• Different properties between elements in the
  first row of a group than the elements in the
  second row due to the large differences in the
  atomic radii
• H is very different from Li due to Hs very small
  size
• H has a greater attraction for electrons than Li,
  so H can form covalent bonds, Li and the other
  Group I elements lose electrons

4
The Representative Elements

• Oxides of Group IIA are basic except
• BeO is amphoteric
• because Be is so small, BeO has some covalent
  character
• Dramatic difference between C chemistry and
  silicon chemistry
• Organic chemistry - deals with stable compounds
  with many C - C bonds
• Silicon chemistry - mostly Si - O bonds.
• Compounds with Si-Si bonds are more reactive

5
The Representative Elements

• Carbon
• can form p bonds, CC, CO, etc.
• Silicon
• difficult to form p bonds
• Sis 3p orbital cannot overlap with Os 2p
  orbital ...due to differences in size

6
The Representative Elements

• Nitrogen
• forms p bonds, e.g. N N, very very stable
• Phosphorus
• like Si, does not form p bonds, though it does
  form aggregates of atoms, like P4
• Oxygen
• forms bonds, e.g. OO, very stable
• Sulfur
• Sulfur atoms form aggregates, such as the cyclic
  S8

7
The Representative Elements

• Still on the subject of size...
• F has a smaller electron affinity than Cl, which
  is the reverse of the expected trend
• Why? F is so small that the electron pairs tend
  to repel each other.
• The F2 bond is weaker than the Cl2 bond, again
  because Fs small size allow the lone pairs to
  get closer together, repelling each other, and so
  weakening the bond

8
The Representative Elements

• Abundance and Preparation
• In the earths crust, oceans and atmosphere
• Oxygen 49.2
• Silicon 25.7
• Aluminum 7.50
• Iron 4.71
• Calcium 3.39

9
The Representative Elements

• Abundance and Preparation
• In the human body
• Oxygen 65.0
• Carbon 18.0
• Hydrogen 10.0
• Nitrogen 3.0
• Calcium 1.4

10
The Representative Elements

• Abundance and Preparation
• Only 1/4 of the elements occur naturally in the
  free state
• Metallurgy - process of obtaining a metal from
  its ore
• usually involves the reduction of the metal
• Carbon is the usual choice for a reducing agent
• Electrolysis is used to reduce the most active
  metals

11
The Representative Elements

• Preparation of Nonmetals
• Liquefaction/distillation of air to obtain N2 and
  O2
• based on their different boiling points
• N2 - second in amount manufactured in the U.S.
• O2 - fourth in amount manufactured in the U.S.
• H2 - obtained from the electrolysis of water and
  the decomposition of methane
• Sulfur - found underground in elemental form,
  recovered using the Frasch process

12
The Representative Elements

• Group IA Elements
• ns1 outer electron configuration
• very active metals (except for hydrogen)
• the alkali metals
• react vigorously with water to produce hydrogen
  gas
• 2M 2 H2O(l) --gt 2 M 2 OH- H2
• Li is the only alkali metal to form the oxide in
  presence of excess oxygen
• 2Li(s) O2(g) --gt 2Li2O(s)

13
The Representative Elements

• 2 Na(s) O2(g) --gt Na2O(s) (in limited oxygen)
• In excess oxygen, sodium forms the peroxide
• 2Na O2 --gt Na2O2
• the sodium peroxide reacts with water to form
  hydrogen peroxide
• Na2O2 2H2O --gt H2O2 2 Na 2OH-
• Potassium, rubidium and cesium react with oxygen
  to produce superoxides, MO2
• Ex K(s) O2(g) --gt KO2(s)
• The superoxides release oxygen gas in water or
  carbon dioxide

14
The Representative Elements

• 2KO2 2H2O --gt 2K 2OH- O2 H2O2
• 4KO2 2CO2 --gt 2K2CO3(s) 3O2
• these superoxides are used in the breathing
  apparatus used by firefighters
• Lithium is the only alkali metal to react with
  nitrogen gas
• 6Li N2 --gt 2Li3N(s)

15
The Representative Elements

• Element Source Method of Preparation
• Lithium silicate minerals electrolysis of molten
  LiCl
• Sodium NaCl electrolysis of molten NaCl
• Potassium KCl electrolysis of molten KCl

16
The Representative Elements

• Hydrogen
• colorless, odorless gas composed of H2 molecules
• low MM, nonpolar, very low B.P. (-253oC), very
  low M.P. (-253oC)
• highly flammable, explosive
• Industrial source reaction of methane and water
• CH4 H2O --gt CO 3H2
• Also a byproduct of cracking large hydrocarbons
  in gasoline production

17
The Representative Elements

• Hydrogen
• pure hydrogen can be produced by the electrolysis
  of water, but not economically feasible
• Industrial uses
• production of ammonia (Haber process)
• hydrogenation of unsaturated vegetable oils
• Chemical Behavior
• typical nonmetal
• forms covalent compounds with other nonmetals
• forms salts with active metals

18
The Representative Elements

• Hydrides
• Ionic (saltlike) hydrides
• when hydrogen combines with very active metals
  from Group I or Group II
• the hydride ion (H-) is a strong reducing agent
• ionic hydrides react violently in water
• LiH H2O --gt H2 Li OH-
• Covalent hydrides
• when hydrogen combines with other nonmetals, e.g.
  in HCl, NH3, CH4, and H2O

19
The Representative Elements

• Metallic hydrides
• formed when transition metal crystals are treated
  with hydrogen gas
• the hydrogen atoms migrate into the crystal
  structure to occupy holes or interstices
• a solid solution is formed
• when these interstitial hydrides are heated, H2
  gas is released
• use these intersitial hydrides for hydrogen gas
  storage

20
The Representative Elements

• Group IIA Elements
• ns2 outer electron configuration
• very reactive
• alkaline earth metal elements
• the oxides of the Group II elements form bases in
  water MO(s) H2O --gt M2 2 OH-
• BeO can act as an acid as well
• BeO(s) 2 OH- H2O --gt Be(OH)4-2
• Group II metals react with water to form H2
• M(s) 2H2O(l) --gt M2 2 OH- H2(g)

21
The Representative Elements

• Source of Group II elements
• electrolysis of molten chlorides of the Group II
  elements
• Heavier Group II elements react with nitrogen or
  hydrogen to form the nitride or hydride salts
• 3 Ca(s) N2 --gt Ca3N2(s)
• Ca(s) H2 --gt CaH2(s)

22
The Representative Elements

• Practical importance of alkaline earth metals
• Calcium
• found in structural minerals in bones and teeth
• Magnesium
• as Mg2 plays a vital role in metabolism and
  muscle function
• used to produce the bright light for photographic
  flash units 2 Mg O2 --gt 2MgO light
• useful structural material, especially when
  alloyed with aluminum (low density and moderate
  strength)
• both Ca2 and Mg2 make water hard
• hard water interferes with detergent action and
  prevents soaps from lathering

23
The Representative Elements

• Group IIIA Elements
• ns2np1
• metallic character increases going down the group
• Boron
• BH3 is actually unstable, while diborane, B2H6,
  is stable
• boranes are electron deficient, so are very
  reactive
• Aluminum
• most abundant metal on earth
• has metallic physical properties (high thermal
  and electrical conductivities, lustrous
  appearance)
• bonds covalently to nonmetals
• Al2O3 is amphoteric

24
The Representative Elements

• Gallium
• unusually low melting point (30oC)
• largest liquid range between the mp and bp (b.p.
  2400oC)
• makes gallium useful for thermometers, especially
  for high temperatures
• expands like water when it freezes
• is amphoteric like aluminum

25
The Representative Elements

• Indium
• chemistry is similar to aluminum and gallium
• can form 1 ion as well as 3 ions
• Thallium
• completely metallic
• Tl2O3 is a basic oxide
• has a 1 and 3 oxidation state

26
The Representative Elements

• Group IVA Elements
• ns2np2
• contains two of the most important elements on
  earth Carbon and Silicon
• all Group IVA elements can form four covalent
  bonds to nonmetals CH4, SiH4, GeBr4, SnCl4, and
  PbCl4
• form tetrahedral molecules with sp3 hybridization

27
The Representative Elements

• Carbon
• can form p bonds
• C-C bond is stronger than the Si-Si bond, so
  carbon chemistry is dominated by the C-C bond,
  while silicon chemistry is dominated by the Si-O
  bond
• 2 allotropic forms found in the earths crust
• diamond and graphite
• buckminsterfullerene, C60, and other related
  substances have been characterized

28
The Representative Elements

• Three oxides of carbon
• CO, carbon monoxide, by-product of incomplete
  combustion of carbon compounds
• CO2, carbon dioxide, product of human and animal
  respiration and combustion of fossil fuels,
  produced in fermentation
• dissolves in water to form an acidic solution
• CO2 H2O --gt H HCO3-
• OCCCO, carbon suboxide!!

29
The Representative Elements

• Silicon
• second most abundant element on earth
• metalloid
• distributed in silica and silicates
• 85 of the earths crust is composed of these
  silica and silicates
• major use is in semiconductors

30
The Representative Elements

• Germanium
• relatively rare element, metalloid, used in
  semiconductors
• Tin
• soft, silvery white metal
• used in alloys such as bronze (Sn Cu), solder
  (Sn Pb), and pewter (Sn, Cu, Bi, and Sb)
• three allotropes
• white tin, gray tin, and brittle tin (all stable
  at different temperatures)

31
The Representative Elements

• Tin
• current use - protective coating (applied
  electrolytically) for steel, especially in food
  containers
• 2 and 4 oxidation states
• Tin(IV) halides contain covalent Sn-X bonds, not
  ionic bonds, behave more like molecular compounds
  than ionic compounds
• Tin(IV) halides are very volatile
• Tin (II) halides are probably ionic, and are less
  volatile
• SnF2 was used in toothpaste

32
The Representative Elements

• Lead
• obtained from the ore, galena, PbS
• melts at a low temperature
• may have been the first metal every obtained from
  its ore (lead was used as early as 3000 B.C.)
• lead is toxicRoman civilization may have
  crumbled partly due to lead poisoning as analysis
  of bones from that era show high lead
  concentrations
• largest commercial use of lead is for electrodes
  in the lead storage battery

33
The Representative Elements

• Lead
• forms 2 and 4 oxidation states
• lead (II) halides exhibit ionic properties
• only PbCl4 and PbBr4 exist (only possible lead
  (IV) halides)
• PbO (lead (II) oxide) - used to glaze ceramics
• PbO2 (lead (IV) oxide) does not exist in nature

34
The Representative Elements

• Group VA elements
• ns2np3
• varied chemical properties among the members of
  the group
• metallic character increases going down the group
• N and P are nonmetals
• Bi and Sb are metallic
• too much energy is required to remove 5
  electrons, so no ionic compound containing Bi5
  or Sb5 exist
• SbCl5 and BiF5 are actually molecular

35
The Representative Elements

• Bi and Sb are strong oxidizing agents in the 5
  oxidation state
• BiF5 is a good fluorinating agent
• BiF5 --gt BiF3 F2
• Bi3 and Sb3 salts are quite common
• All of the Group VA elements, except for N, can
  form molecules with 5 covalent bonds
• N cannot form molecules with covalent bonds
  because of its small size and lack of d orbitals

36
The Representative Elements

• Elements in Group VA, except for N, do not
  readily form pi bonds
• N2 consists of a triple bond between the nitrogen
  atoms
• P4, As4, and Sb4 are all singly bonded

37
The Representative Elements

• The Chemistry of Nitrogen
• all elemental nitrogen on earth exists as N2 with
  a very strong triple bond (941 kJ/mole)
• N2 is very unreactive it can coexist with most
  other elements without any significant reaction
• N2 makes a good inert atmosphere to run reactions
  with substances that normally react with oxygen
  or water
• Because of N2s triple bond, most binary
  compounds containing nitrogen decompose
  exothermically to form N2
• e.g. N2O --gt N2 1/2 O2 DHo -82 kJ

38
The Representative Elements

• Thermodynamic stability of N2
• nitrogen based explosives
• 4C3H5N3O9(l) --gt 6 N2(g) 12 CO2(g) 10H2O(g)
  O2(g) energy
• nitroglycerin
• 4 moles of liquid nitroglycerin yields 29 moles
  of gaseous products, producing a large increase
  in volume as well as very stable molecules with
  strong bonds, hence an explosion occurs with hot,
  rapidly expanding gases
• Dynamite - invented by Alfred Nobel in 1867
• absorb this highly unstable nitroglycerin onto
  porous silica to make its handling safer

39
The Representative Elements

• More Nitrogen based explosives
• most high explosives are organic compounds that
  contain nitro (-NO2) groups to produce nitrogen
  and other gases as products
• TNT - trinitotoluene
• 2C7H5N3O6(s) --gt 12CO(g) 5H2(g) 2C(s) energy

40
The Representative Elements

• Nitrogen fixation
• transforming N2 to other nitrogen containing
  compounds
• Haber process, the synthesis of ammonia, is an
  example of nitrogen fixation
• the ammonia can be applied to the soil as a
  fertilizer
• high temperature combustion process in automobile
  engines
• nitrogen reacts with oxygen to form NO
• NO reacts with oxygen to form NO2 (contributor to
  photochemical smog)
• NO2 reacts with moisture to form nitrate salts,
  which are plant nutrients

41
The Representative Elements

• Natural nitrogen fixation
• N2 O2 react together to form nitrogen oxides
  with the help of lightning to disrupt the strong
  bonds
• studies indicate that lightning may account for
  half of the fixed nitrogen available on earth
• Nitrogen fixing bacteria in the root nodules of
  legumes such as beans,peas, and alfalfa, allow
  for the conversion of N2 to ammonia and other
  nitrogen containing compounds useful to plants
• much more efficient than the Haber process
  (bacteria work at soil temperature and 1 atm
  pressure, the Haber process runs at 400oC and 250
  atm!

42
The Representative Elements

• The Nitrogen Cycle
• 10 million more tons more nitrogen is currently
  being fixed by natural and human processes than
  is being returned to the atmosphere
• the fixed nitrogen accumulates in the soil,
  lakes, rivers, and oceans where it promotes algae
  growth as well as growth of other undesirable
  organisms
• Denitrification - bacteria can return the
  nitrogen in nitrogen containing compounds to the
  atmosphere as nitrogen gas

43
The Representative Elements

• Nitrogen Hydrides
• Ammonia - most important of the nitrogen hydrides
• toxic, colorless gas, manufactured in large
  quantities (30 billion pounds per year, used
  mainly in fertilizers
• unusually high B.P. (-33.4oC), for a substance
  with such a low MM, due to Hydrogen bonding
• Hydrazine, N2H4
• colorless liquid with an ammonia-like odor
• powerful reducing agent
• used as a rocket propellant
• used as a blowing agent (because it produces
  N2(g) upon decomposition) in the manufacture of
  plastics
• used in agricultural pesticides

44
The Representative Elements

• Nitrogen Oxides
• Nitrogen forms a series of oxides in which
  nitrogen has oxidation states from 1 to 5
• N2O - dinitrogen monoxide, aka, nitrous oxide,
  aka, laughing gas
• also a mild anesthetic, a propellant in aerosol
  cans of whipped cream
• exists in the atmosphere as a result of soil
  microorganisms, helps to control the earths
  temperature because it can absorb infrared
  radiation

45
The Representative Elements

• Nitrogen Monoxide
• NO, commonly called nitric oxide
• colorless gas produced when nitric acid reacts
  with copper metal
• in oxygen, the NO is oxidized to form the brown
  gas, NO2
• may behave as a neurotransmitter in the body
• has an odd number of electrons, is paramagnetic
  (use MO diagrams), and is thermodynamically
  unstable
• 3NO(g) --gt N2O(g) NO2(g)

46
The Representative Elements

• Nitrogen Dioxide
• NO2, also contains an odd number of electrons, is
  paramagnetic, and dimerizes to form N2O4
• 2NO2 --gt N2O4
• Dinitrogen Trioxide
• N2O3 - least common, a blue liquid that
  dissociates into NO and NO2, and N2O5

47
The Representative Elements

• Oxyacids of Nitrogen
• Nitric acid - HNO3
• 10 million tons produced per year
• used in the manufacture of many products such as
  nitrogen based explosives and ammonium nitrate
• produced commercially by the oxidation of ammonia
  in the Ostwald process
• 4NH3 5O2 --gt 4NO 6 H2O
• 2NO O2 --gt 2NO2
• 3NO2 H2O --gt 2HNO3 NO

48
The Representative Elements

• Nitric acid
• colorless, fuming liquid with a pungent odor
• decomposes in sunlight
• 4HNO3 --gt 4NO2 2 H2O O2
• turns yellow as it ages because of the NO2
• strong oxidizing agent
• reacts with metal oxides, hydroxides, and
  carbonates to form nitrate salts which are
  generally very soluble in water

49
The Representative Elements

• Nitrous Acid
• HNO2, a weak acid, forms pale yellow nitrite
  salts
• nitrites are very stable, even at high
  temperatures
• nitrites are prepared by bubbling nitric oxide,
  nitrogen dioxide, and a metal hydroxide
• NO NO2 2NaOH --gt 2NaNO2 H2O

50
The Representative Elements

• The Chemistry of Phosphorus
• very different properties from those of nitrogen
• due to
• Ns ability to form pi bonds
• greater electronegativity of N
• larger size of P
• availability of d orbitals on phosphorus
• several solid forms of phosphorus
• white phosphorus, P4, with a tetrahedral geometry
• very reactive, bursts into flames on contact with
  air (it is pyrophoric)

51
The Representative Elements

• Black phosphorus and red phosphorus - covalent
  network solids
• Black phosphorus is crystalline, and is obtained
  from white or red phosphorus
• Red phsophorus is amorphous and is obtained from
  heating white phosphorus in the absence of air
• Phosphide salts react with water to produce
  phosphine, PH3, a toxic, colorless gas

52
The Representative Elements

• Phosphorus oxides and oxyacids
• Phosphorus reacts with oxygen to form oxides in
  which P has oxidation states 5 and 3.
• P4O6, P4O7, P4O8, P4O9, and P4O10 can be obtained
  by burning phosphorus in oxygen
• P4O10 is powerful dehydrating agent
• it can convert HNO3 and H2SO4 to their parent
  oxides, N2O5 and SO3
• P4O10 reacts with water to form phosphoric acid
• P4O10 6H2O --gt 4H3PO4

53
The Representative Elements

• Phosphoric acid undergoes condensation reactions
• water is eliminated as two molecules of
  phosphoric acid are joined together
• H3PO3 is actually a diprotic acid as one H is
  bonded to the P
• H3PO2 is actually a monoprotic acid as two Hs
  are bonded to the P

54
The Representative Elements

• Phosphorus is essential for plant growth
• usually present as insoluble phosphate minerals,
  inaccessible to plants
• make accessible with soluble phosphate fertilizers

55
The Representative Elements

• Phosphorus Halides
• PX3 and PX5 exist for all halides except PI5 does
  not exist
• PX3 reacts with water to form phosphorus acid
• PCl3 3H2O --gt H3PO3 3HCl
• PCl5 and PBr5 form ionic solidsPCl5 contain a
  mixture of the PCl6- ion and PCl4 ion
• PBr5 contains a mixture of PBr4 and Br- ion
• PX5 reacts with water to form phosphoric acid
• PX5 4H2O --gt H3PO4 5HX

56
The Representative Elements

• Group VIA elements
• ns2np4
• metallic behavior increases going down the group,
  but none of the Group 6A elements behaves as a
  typical metal
• can form covalent bonds with other nonmetals
• Te and Po can exist as 4 cations, but their
  chemistry is limited

57
The Representative Elements

• Selenium
• studies show an inverse relationship between
  incidence of cancer of selenium levels in
  soili.e., the more selenium in the soil, the
  lower the incidence of cancer
• involved in the activity of Vitamin E and other
  enzymes
• selenium deficiency is connected to occurrence of
  congestive heart failure
• used as semiconductors

58
The Representative Elements

• Polonium
• discovered by Marie Curie in 1898
• has 27 isotopes
• highly toxic and very radioactive
• 210Po is found in tobacco, is an alpha particle
  emitter, and so may be responsible for the
  incidence of cancer in smokers

59
The Representative Elements

• The Chemistry of Oxygen
• Most abundant element in and near the earths
  crust
• Present as O2, in oxide, silicate, and carbonate
  minerals, in water, and in many more molecules
• O2 makes up 21 by volume of the atmosphere
• freezes at -219oC and boils at -183oC
• can be obtained from liquid air after N2 has been
  removed
• a pale blue liquid
• paramagnetic (see M.O. model)

60
The Representative Elements

• The Chemistry of Oxygen
• Ozone - an allotrope of oxygen, O3
• can be prepared by passing an electric discharge
  through O2
• pale blue, highly toxic gas
• powerful oxidizing agent, can be used instead of
  chlorine in water purification
• exists naturally in the upper atmosphere of the
  earth
• protects from uv, the O3 absorbs the energy and
  splits
• O3 --gt O2 O

61
The Representative Elements

• The Chemistry of Sulfur
• found as the free element
• found in ores such as galena (PbS), cinnabar
  (HgS), pyrite (FeS), gypsum (CaSO4.2H2O), etc.
• 60 of the sulfur produced in the U.S. comes from
  deposits of underground sulfur from Texas and
  Louisiana
• Sulfur is recovered using the Frasch process
  developed by Herman Frasch in the 1890s

62
The Representative Elements

• The Chemistry of Sulfur
• Frasch Process
• superheated water is pumped into the deposit to
  melt the sulfur
• the molten sulfur is forced to the surface using
  air pressure
• the remaining 40 of the sulfur comes from the
  purification of fossil fuels, from the sulfur
  dioxide obtained from the burning of sulfur
  containing fuels

63
The Representative Elements

• Sulfur atoms from strong s bonds than p bonds
• large aggregates of S6and S8 and Sn exist
• Most stable form rhombic sulfur which consists
  of stacked rings of S8
• An allotropic form of the rhombic sulfur is the
  monoclinic sulfur which is also S8, but which are
  stacked differently than in rhombic sulfur
• A plastic sulfur also exists which contains Sn
  chains and has rubber like qualities.

64
The Representative Elements

• Sulfur Oxides
• S burns in air to give SO2
• SO2 is an effective antibacterial agent and is
  used to preserve dry fruit
• 2SO2 O2 --gt 2SO3
• produced when sulfur containing fuels are burned
• a slow reaction that requires a catalyst
• SO3 is a corrosive gas
• forms H2SO4 when it reacts with moisture in the
  air, a culprit in acid rain

65
The Representative Elements

• Oxyacids of Sulfur
• SO2 H2O --gt H2SO3
• SO3 H2O --gt H2SO4 (very violent reaction)
• Sulfuric acid
• manufactured in greater amounts than any other
  chemical
• 60 of the H2SO4 is used to produce fertilizers
• 40 is used in lead storage batteries, in
  petroleum refining, steel manufacturing and in
  other chemical industries

66
The Representative Elements

• Sulfuric Acid
• high affinity for water - acts as a dehydrating
  agent
• dry gases by bubbling gases through concentrated
  sulfuric acid
• it can even remove H and O in a 21 ratio from
  sugar
• C12H22O11 11H2SO4 --gt 12C(s) 11 H2SO4. H2O
• strong oxidizing agent, especially at high
  temperatures
• SO4-2--gt SO2

67
The Representative Elements

• Other Compounds of Sulfur
• Oxidation states of sulfur 6, 4, 2, 0, and -2
• H2S - sulfur has a -2 oxidation state
• toxic, foul smelling gas
• good reducing agent
• produces a milking looking suspension of sulfur
  as one of the products H2S(g) --gt S(s)

68
The Representative Elements

• Other Compounds of Sulfur
• thiosulfate ion S2O3-2
• similar to a sulfate ion, but one of the oxygens
  has been replaced with a sulfur atom
• used in photography
• S(s) SO3-2 --gt S2O3-2
• good reducing agent S2O3-2 --gt S4O6-2 (used to
  analyze for Iodine)
• sulfur reacts with halogens to form a variety of
  compounds S2Cl2, SF4, SF6, S2F10, etc.

69
The Representative Elements

• Group VIIA elements
• halogens
• ns2np5
• all nonmetals whose properties vary smoothly
  going down the group
• exceptions include the low electron affinity of F
  and the bond energy of the F2 molecule which is
  lower than expected
• Astatines isotopes are all radioactive

70
The Representative Elements

• Halogens
• all high electronegativity values, especially F
• tend to form polar covalent bonds with other
  nonmetals
• form ionic bonds with metals in their lower
  oxidation states
• the bonds become polar covalent when a halogen is
  bonded with a metal in a higher oxidation state,
  e.g. TiCl4 or SnCl4 (both covalent compounds and
  liquids under normal conditions)