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PeriodicProperties
of the Elements
Chapter 7Periodic Properties
of the Elements
Chemistry, The Central Science, 10th editionTheodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
John D. BookstaverSt. Charles Community College
St. Peters, MO 2006, Prentice Hall, Inc.
PeriodicProperties
of the Elements
November 9
• For Monday finish chapter 7 and do all the questions in the worksheet.
• Test on chapter 6 and 7 on Tuesday.
• Equation book review Chapter 2 and 3
PeriodicProperties
of the Elements
Anomalies
• Cr 3d5 4s1
• Mo• Cu• Ag• Au• The energies between 3d and 4s are close,
and to have a sublevel half filled or completely filled gives stability to the atom.
PeriodicProperties
of the Elements
Paramagnetism
• Elements and compounds that have unpaired electrons are attracted to a magnet. The effect is weak but it can be observed.
• Liquid O2 attracted to a magnet.
PeriodicProperties
of the Elements
Diagmagnetism
• Substances with no unpaired electrons experiment a slight repulsion when subjected to a magnetic field.
PeriodicProperties
of the Elements
• http://books.google.com/books?id=jcn6sgt7RpoC&lpg=PA405&ots=0AV83UNudy&dq=paramagnetism%20images%20kotz&pg=PA293#v=onepage&q&f=false
PeriodicProperties
of the Elements
Development of Periodic Table
• Elements in the same group generally have similar chemical properties.
• Properties are not identical, however.
PeriodicProperties
of the Elements
Development of Periodic Table
Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped in 1869.
PeriodicProperties
of the Elements
PERIODIC ARRANGEMENT
• Mendeleev arranged the elements according to their atomic masses.
• In 1913 Henry Moseley developed the concept of ATOMIC NUMBERS which lead to the current arrangement according to their ATOMIC NUMBER.
PeriodicProperties
of the Elements
Effective Nuclear Charge
• In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons.
• The nuclear charge that an electron experiences depends on both factors.
PeriodicProperties
of the Elements
Effective Nuclear Charge
The effective nuclear charge, Zeff, is found this way:
Zeff = Z − S
where Z is the atomic number and S is a screening constant, usually close to the number of inner electrons.
PeriodicProperties
of the Elements
Effective Nuclear Charge
• The effective nuclear charge is smaller than the actual nuclear charge because the effective nuclear charge Zeff
accounts for the repulsion of the electron by the other electrons in the atom.
• Zeff < Z
PeriodicProperties
of the Elements
• Core electrons shield or screen the outer electrons from the attraction of the nucleus.
PeriodicProperties
of the Elements
Sizes of Atoms
The bonding atomic radius is defined as one-half of the distance between covalently bonded nuclei.
PeriodicProperties
of the Elements
Sizes of AtomsBonding atomic radius tends to… …decrease from left to
right across a rowdue to increasing Zeff.
…increase from top to bottom of a column
due to increasing value of n
PeriodicProperties
of the Elements
Examples – Place each group of elements in order of increasing atomic radius:
1. S, Al, Cl, Mg, Ar, Na
2. K, Li, Cs, Na, H
3. Ca, As, F, Rb, O, K, S, Ga
PeriodicProperties
of the Elements
Examples – Place each group of elements in order of increasing atomic radius:
1. S, Al, Cl, Mg, Ar, Na
Ar < Cl < S < Al < Mg < Na
2. K, Li, Cs, Na, H
H < Li < Na < K < Cs
3. Ca, F, As, Rb, O, K, S, Ga
F < O < S < As < Ga < Ca < K < Rb
PeriodicProperties
of the Elements
Electron Configurations of Ions• Cations: electrons removed from orbital with highest
principle quantum number, n, first:
Li (1s2 2s1) Li+ (1s2)
Fe ([Ar]3d6 4s2) Fe3+ ([Ar]3d5) • Anions: electrons added to the orbital with highest n:
F (1s2 2s2 2p5) F (1s2 2s2 2p6)
PeriodicProperties
of the Elements
Write electron configurations for the following ions:
1. Al3+
2. S2-
3. Li+
4. Br-
5. Fe2+
6. Fe3+
PeriodicProperties
of the Elements
Write electron configurations for the following ions:
1. Al3+ 1s22s22p6
2. S2- [Ne]3s23p6
3. Li+ 1s2
4. Br- [Ar]4s23d104p6
5. Fe2+ [Ar]3d6
6. Fe3+ [Ar]3d5
PeriodicProperties
of the Elements
Sizes of Ions• Ionic size depends
upon:Nuclear charge.Number of
electrons.Orbitals in which
electrons reside.
PeriodicProperties
of the Elements
Sizes of Ions• Cations are
smaller than their parent atoms.The outermost
electron is removed and repulsions are reduced.
PeriodicProperties
of the Elements
Sizes of Ions• Anions are larger
than their parent atoms.Electrons are
added and repulsions are increased.
PeriodicProperties
of the Elements
Sizes of Ions
• Ions increase in size as you go down a column.Due to increasing
value of n.
PeriodicProperties
of the Elements
November 10
• DO NOW• Write the formula for • Potassium Permanganate and Sodium
hypochlorite• Write the electronic configuration of
both cations. Indicate to what element are each isoelectronic.
• Which one has the largest radius?
PeriodicProperties
of the Elements
Homework• New Atomic Theory Exams Questions
is a file in the John Bowne site. Has similar questions to AP test. Practice them. The more you do them the better you’ll do in the test.
Test Unit 6 and 7 Tuesday
PeriodicProperties
of the Elements
Sizes of Ions
• In an isoelectronic series, ions have the same number of electrons.
• Ionic size decreases with an increasing nuclear charge.
PeriodicProperties
of the Elements
Examples – Choose the larger species in each case:
1. Na or Na+
2. Br or Br-
3. N or N3-
4. O- or O2-
5. Mg2+ or Sr2+
6. Mg2+ or O2-
7. Fe2+ or Fe3+
PeriodicProperties
of the Elements
Examples – Choose the larger species in each case:
1. Na or Na+
2. Br or Br-
3. N or N3-
4. O- or O2-
5. Mg2+ or Sr2+
6. Mg2+ or O2-
7. Fe2+ or Fe3+
PeriodicProperties
of the Elements
Ionization Energy
• Amount of energy required to remove an electron from the ground state of a gaseous atom or ion.First ionization energy is that energy
required to remove first electron.Second ionization energy is that energy
required to remove second electron, etc.
PeriodicProperties
of the Elements
IONIZATION ENERGY
• THE GREATER THE IONIZATION ENERGY THE MORE DIFFICULT IT IS TO REMOVE AN ELECTRON!
• It requires more energy to remove each successive electron.
• When all valence electrons have been removed, the ionization energy takes a quantum leap (removing core electrons require huge amounts of energy).
PeriodicProperties
of the Elements
PeriodicProperties
of the Elements
Trends in First Ionization Energies
• As one goes down a column, less energy is required to remove the first electron.For atoms in the same
group, Zeff is essentially the same, but the valence electrons are farther from the nucleus.
PeriodicProperties
of the Elements
Trends in First Ionization Energies
• Generally, as one goes across a row, it gets harder to remove an electron.As you go from left to
right, Zeff increases.
PeriodicProperties
of the Elements
Irregularities
• N 1402
• [He] 2s2 2p3
• 2p3 this configuration is more stable because half filled orbitals minimize repulsions between electrons
• O 1314
• [He] 2s2 2p4
• The decrease is due to repulsions of paired electrons in 2p4
PeriodicProperties
of the Elements
Trend across a periodIE icreases
• The energy needed to remove an electron increases because the effective nuclear charge increases and the atomic radius decreases.
• Irregularities
• Be 899 B 801
• [He] 2s2 [He] 2s2 2p1
PeriodicProperties
of the Elements
Trends in First Ionization Energies
However, there are two apparent discontinuities in this trend.
PeriodicProperties
of the Elements
Trends in First Ionization Energies
• The first occurs between Groups IIA and IIIA.
• Electron removed from p-orbital rather than s-orbitalElectron farther from
nucleusSmall amount of
repulsion by s electrons.
PeriodicProperties
of the Elements
Trends in First Ionization Energies
• The second occurs between Groups VA and VIA.Electron removed
comes from doubly occupied orbital.
Repulsion from other electron in orbital helps in its removal.
PeriodicProperties
of the Elements
Examples – Put each set in order of increasing first ionization energy:
1. P, Cl, Al, Na, S, Mg
2. Ca, Be, Ba, Mg, Sr
3. Ca, F, As, Rb, O, K, S, Ga
PeriodicProperties
of the Elements
Examples – Put each set in order of increasing first ionization energy:
1. P, Cl, Al, Na, S, Mg
2. Ca, Be, Ba, Mg, Sr
3. Ca, F, As, Rb, O, K, S, Ga
1. Na < Al < Mg < S < P < Cl
2. Ba < Sr < Ca < Mg < Be
3. Rb < K < Ga < Ca < As < S < O < F
PeriodicProperties
of the Elements
Electron Affinity
• It measures the ease with which and atom gains an electron
PeriodicProperties
of the Elements
Electron Affinity
Energy change accompanying addition of electron to gaseous atom:
Cl + e− Cl−
For most atoms energy is released when an electron is added. The change is exothermic. The more exothermic the most stable the product.
PeriodicProperties
of the Elements
Trends in Electron Affinity
In general, electron affinity becomes more exothermic as you go from left to right across a row.
PeriodicProperties
of the Elements
Trends in Electron Affinity
There are again, however, two discontinuities in this trend.
PeriodicProperties
of the Elements
Trends in Electron Affinity
• The first occurs between Groups IA and IIA.Added electron must
go in p-orbital, not s-orbital.
Electron is farther from nucleus and feels repulsion from s-electrons.
PeriodicProperties
of the Elements
Trends in Electron Affinity
• The second occurs between Groups IVA and VA.Group VA has no
empty orbitals.Extra electron must
go into occupied orbital, creating repulsion.
PeriodicProperties
of the Elements
November 11
• Do now
• Find the Oxidation Number for Oxygen in
• KO2
• K2O2
• KO2
• Name the compounds
PeriodicProperties
of the Elements
• Electronegativity: The ability of an atom in a molecule to attract electrons to itself.
• Pauling set electronegativities on a scale from 0.7 (Cs) to 4.0 (F). Values are calculated from ionization energies and electron affinities.
• Electronegativity increases • across a period and
• Up a group.
PeriodicProperties
of the Elements
Electronegativity
PeriodicProperties
of the Elements
Examples – put each set in order by increasing electronegativity:
1. Na, Li, Rb, K, Fr
2. Cl, Ca, F, P, Mg, S, K
PeriodicProperties
of the Elements
Examples – put each set in order by increasing electronegativity:
1. Na, Li, Rb, K, Fr
2. Cl, Ca, F, P, Mg, S, K
1. Fr < Rb < K < Na < Li
2. K < Ca < Mg < P < S < Cl < F
PeriodicProperties
of the Elements
Properties of Metal, Nonmetals,and Metalloids
PeriodicProperties
of the Elements
Metals versus Nonmetals
Differences between metals and nonmetals tend to revolve around these properties.
PeriodicProperties
of the Elements
Metals versus Nonmetals
• Metals tend to form cations.• Nonmetals tend to form anions.
PeriodicProperties
of the Elements
Metals
Tend to be lustrous, malleable, ductile, and good conductors of heat and electricity.
PeriodicProperties
of the Elements
Metallic Trend
• Metals react by losing electrons and forming cations. Metallic character increases with the easiness of losing electrons. The trend is like the ionization energy. Decreases across a period and increases down a group.
PeriodicProperties
of the Elements
Metals
• Compounds formed between metals and nonmetals tend to be ionic.
• Metal oxides tend to be basic.
PeriodicProperties
of the Elements
Nonmetals
• Dull, brittle substances that are poor conductors of heat and electricity.
• Tend to gain electrons in reactions with metals to acquire noble gas configuration.
PeriodicProperties
of the Elements
Nonmetals
• Substances containing only nonmetals are molecular compounds.
• Most nonmetal oxides are acidic.
PeriodicProperties
of the Elements
Metalloids
• Have some characteristics of metals, some of nonmetals.
• For instance, silicon looks shiny, but is brittle and fairly poor conductor.
PeriodicProperties
of the Elements
Group Trends
PeriodicProperties
of the Elements
Metals• Most metal oxides are basic: (NOT A REDOX RX!!!)
Metal oxide + water metal hydroxideNa2O(s) + H2O(l) 2NaOH(aq)
Nonmetals• Nonmetals are more diverse in their behavior than metals.• When nonmetals react with metals, nonmetals tend to
gain electrons (reduced):metal + nonmetal salt
2Al(s) + 3Br2(l) 2AlBr3(s)
PeriodicProperties
of the Elements
Nonmetals• Most nonmetal oxides are acidic:
nonmetal oxide + water acid (NON A REDOX RX)
P4O10(s) + H2O(l) 4H3PO4(aq)
Metalloids• Metalloids have properties that are intermediate between
metals and nonmetals.• Example: Si has a metallic luster but it is brittle.• Metalloids have found application in the semiconductor
industry.
PeriodicProperties
of the Elements
Alkali Metals
• Soft, metallic solids.• Name comes from
Arabic word for ashes.
PeriodicProperties
of the Elements
moviealkalimetals.mp4Alkali Metals
• Found only as compounds in nature. Very reactive!!!
• Have low densities and melting points.• Also have low ionization energies.
PeriodicProperties
of the Elements
Alkali Metals
Their reactions with water are famously exothermic.
They react vigorously with water and have to be stored in mineral oil or kerosene.
2M (s) + 2 H2 O (l) 2MOH (aq) + H2 (g)
PeriodicProperties
of the Elements
Alkali Metals Reactions
• Alkali metals combine directly with most nonmetals Alkali metals (except Li) react with oxygen to form peroxides. (O2
2- remember ON -1 )
• K, Rb, and Cs also form superoxides:
K + O2 KO2 (ON -1/2!!)
• Alkali metals produce different oxides when reacting with O2:
• 4Li(s) + O2(g) 2Li2O(s) (oxide)
• 2Na(s) + O2(g) Na2O2(s) (peroxide)
• K(s) + O2(g) KO2(s) (superoxide)
PeriodicProperties
of the Elements
With Hydrogen they form HYDRIDES (H-) LiH, KH
With Sulfur they form Sulfides
PeriodicProperties
of the Elements
Na line (589 nm): 3p 3s transition
Li line: 2p 2s transition
K line: 4p 4s transition
Group Trends for the Group Trends for the Active MetalsActive Metals
Group 1: The Alkali MetalsProduce bright colors when placed in flame.
PeriodicProperties
of the Elements
Alkaline Earth Metals
• Have higher densities and melting points than alkali metals.
• Have low ionization energies, but not as low as alkali metals.
PeriodicProperties
of the Elements
Alkaline Earth Metals
• Be does not react with water, Mg reacts only with steam, but others react readily with water.
• Reactivity tends to increase as go down group. They are less reactive than Alkali metals.
PeriodicProperties
of the Elements
Flame Test Colors
• Ca2+ Orange-red
• Sr2+ Crimson Red
• Ba2+ Pale Green
• They are used in firework!
PeriodicProperties
of the Elements
Group 6A
• Oxygen, sulfur, and selenium are nonmetals.• Tellurium is a metalloid.• The radioactive polonium is a metal.
PeriodicProperties
of the Elements
Oxygen• Two allotropes:
O2
O3, ozone
• Three anions:O2−, oxideO2
2−, peroxideO2
1−, superoxide
• Tends to take electrons from other elements (oxidation)
PeriodicProperties
of the Elements
Sulfur
• Weaker oxidizing agent than oxygen.
• Most stable allotrope is S8, a ringed molecule.
PeriodicProperties
of the Elements
Group VIIA: Halogens
• Prototypical nonmetals• Name comes from the Greek halos and
gennao: “salt formers”
PeriodicProperties
of the Elements
Group VIIA: Halogens
• Large, negative electron affinitiesTherefore, tend to oxidize
other elements easily
• React directly with metals to form metal halides
• Chlorine added to water supplies to serve as disinfectant
PeriodicProperties
of the Elements
Group 17: The Halogens• The chemistry of the halogens is dominated by gaining
an electron to form an anion:
X2 + 2e- 2X-.
• Fluorine is one of the most reactive substances known:
2F2(g) + 2H2O(l) 4HF(aq) + O2(g) H = -758.7 kJ.
SiO2 (s) + 2F2(g) SiF4 (g) + O2 (g) H = -704.0 kJ
• Why is it so reactive?
• All halogens consist of diatomic molecules, X2.
PeriodicProperties
of the Elements
• Chlorine is the most industrially useful halogen. It is produced by the electrolysis of brine (NaCl):
2NaCl(aq) + 2H2O(l) 2NaOH(aq) + H2(g) + Cl2(g).
• The reaction between chorine and water produces hypochlorous acid (HOCl) which disinfects pool water:
Cl2(g) + H2O(l) HCl(aq) + HOCl(aq).
• Halogens react directly with metals to form ionic halides
H2 (g) + X2 2 HX (g)
• Hydrogen compounds of the halogens are all strong acids with the exception of HF.
• LEARN THESE REACTIONS!!!
PeriodicProperties
of the Elements
Group VIIIA: Noble Gases
• Astronomical ionization energies• Positive electron affinities
Therefore, relatively unreactive
• Monatomic gases
PeriodicProperties
of the Elements
Group VIIIA: Noble Gases
• Xe forms three compounds:XeF2
XeF4 (at right)
XeF6
• Kr forms only one stable compound:KrF2
• The unstable HArF was synthesized in 2000.