Periodic Properties of the Elements Chapter 7 Periodic Properties of the Elements Chemistry, The...

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


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


• 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

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


• 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


However, there are two apparent discontinuities in this trend.

PeriodicProperties

of the Elements


• 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


• 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


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


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


There are again, however, two discontinuities in this trend.

PeriodicProperties

of the Elements


• 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


• 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.

Periodic Properties of the Elements Chapter 7 Periodic Properties of the Elements Chemistry, The...

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