Periodic TablePeriodic Table

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The Periodic Table-Key QuestionsThe Periodic Table-Key QuestionsWhat is the periodic table ?What information does the table provide ?How can one use the periodic table to predict the properties of the elements??

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Periodic TablePeriodic Table• The development of the periodic table brought a The development of the periodic table brought a

system of order to what was otherwise an system of order to what was otherwise an collection of thousands of pieces of collection of thousands of pieces of information. information.

• The periodic table is a milestone in the The periodic table is a milestone in the development of modern chemistry. It not only development of modern chemistry. It not only brought order to the elements but it also brought order to the elements but it also enabled scientists. enabled scientists.

to predict the existence

of elements that had

not yet been discovered .

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Dmitri MendeleevDmitri Mendeleev Dmitri Mendeleev is

credited with creating the modern periodic table of the elements.

He gets the credit because he not only arranged the atoms, but he also made predictions based on his arrangements His predictions were later shown to be quite accurate.

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MendeleevMendeleev’’s Periodic Tables Periodic Table

• Mendeleev organized all of the elements into one comprehensive table.

• Elements were arranged in order of increasing mass.

• Elements with similar properties were placed in the same row.

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MendeleevMendeleev’’s Periodic Tables Periodic Table

Mendeleev left some blank spaces in his periodic table. At the time the elements gallium and germanium were not known. He predicted their discovery and estimated their properties. .6

The Modern Periodic TableThe Modern Periodic Table

The Periodic Table has undergone several modifications before it evolved in its present form. The current form is usually attributed to Glenn Seaborg in 1945

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The Three Broad Classes are the The Three Broad Classes are the Representative, Transition, & Rare Representative, Transition, & Rare

EarthEarthMain (Representative), Transition metals, lanthanides and actinides (rare earth)

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Periodic Table: Periodic Table: The electron The electron configurations are inherent in the configurations are inherent in the

periodic tableperiodic table

BB2p2p11

H1s1

Li2s1

Na3s1

K4s1

Rb5s1

Cs6s1

Fr7s1

Be2s2

Mg3s2

Ca4s2

Sr5s2

Ba6s2

Ra7s2

Sc3d1

Ti3d2

V3d3

Cr4s13d5

Mn3d5

Fe3d6

Co3d7

Ni3d8

Zn3d10

Cu4s13d10

B2p1

C2p2

N2p3

O2p4

F2p5

Ne2p6

He1s2

Al3p1

Ga4p1

In5p1

Tl6p1

Si3p2

Ge4p2

Sn5p2

Pb6p2

P3p3

As4p3

Sb5p3

Bi6p3

S3p4

Se4p4

Te5p4

Po6p4

Cl3p5

Be4p5

I5p5

At6p5

Ar3p6

Kr4p6

Xe5p6

Rn6p6

Y4d1

La5d1

Ac6d1

Cd4d10

Hg5d10

Ag5s14d10

Au6s15d10

Zr4d2

Hf5d2

Rf6d2

Nb4d3

Ta5d3

Db6d3

Mo5s14d5

W6s15d5

Sg7s16d5

Tc4d5

Re5d5

Bh6d5

Ru4d6

Os5d6

Hs6d6

Rh4d7

Ir5d7

Mt6d7

Ni4d8

Ni5d8

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Periodic Table Periodic Table Organization------ Groups or Organization------ Groups or

FamiliesFamilies

Vertical columns in the periodic table are known as groups or families The elements in a group have similar electron configurations

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Periodic Table Organization Periodic Table Organization ---- Periods ---- Periods

Horizontal Rows in the periodic table are known as Periods The Elements in a period undergo a gradual change in properties as one proceeds from left to right

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Periodic PropertiesPeriodic PropertiesElements show gradual changes in certain physical properties as one moves across a period or down a group in the periodic table. These properties repeat after certain intervals. In other words they are PERIODIC

Periodic Periodic properties properties include:include:

-- Ionization Energy-- Electronegativity-- Atomic Radius-- Ionic Radius

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Metals lose electrons more easily than nonmetals.Nonmetals lose electrons with difficulty. (They like to GAIN electrons). Ionization energy increases across a period because the positive charge increases.

Ionization energy is the energy required toremove an electron from an atom

Trends in Ionization EnergyTrends in Ionization Energy

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The ionization energy is The ionization energy is highest at the top of a highest at the top of a group. Ionization energy group. Ionization energy decreases as the atom decreases as the atom size increases. size increases. This results from an This results from an effect known as the effect known as the Shielding Effect Shielding Effect

Trends in Ionization EnergyTrends in Ionization Energy

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Ionization Energies of the Ionization Energies of the Representative GroupsRepresentative Groups

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Ionization Energies are Periodic

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Effective Nuclear ChargeEffective Nuclear Charge

Many properties depend on:Many properties depend on:– Electron configurationElectron configuration– How strong outer electrons are attracted to How strong outer electrons are attracted to

nucleusnucleus

Effective nuclear charge: net electrical Effective nuclear charge: net electrical charge acting on an electroncharge acting on an electron– Increases with nuclear charge (number of Increases with nuclear charge (number of

protons)protons)– Decreases with distance from nucleusDecreases with distance from nucleus

Effective Nuclear ChargeEffective Nuclear Charge

Shielding: repulsion of inner electrons on Shielding: repulsion of inner electrons on outer electrons, reducing the effect of the outer electrons, reducing the effect of the nuclear charge on electronsnuclear charge on electrons

ZZeffeff = Z – S = Z – S

– Z = number of protonsZ = number of protons– S = number of non valence electronsS = number of non valence electrons

The Electron Shielding EffectThe Electron Shielding Effect

Electrons between the nucleus and the valence electrons repel each other making the atom larger.

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ElectronegativityElectronegativity

Electronegativity is a measure of the ability of an atom in a molecule to attract electrons to itself.

This concept was first proposed by Linus Pauling (1901-1994). He later won the Nobel Prize for his efforts.

This concept was first proposed by Linus Pauling (1901-1994). He later won the Nobel Prize for his efforts.

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Periodic Trends: Periodic Trends: ElectronegativityElectronegativity

In a group:In a group: Atoms with fewer Atoms with fewer energy levels can attract energy levels can attract electrons better (less shielding). electrons better (less shielding). So, electronegativity So, electronegativity increases increases UPUP a group of elements. a group of elements.

In a period:In a period: More protons, while More protons, while the energy levels are the same, the energy levels are the same, means atoms can better attract means atoms can better attract electrons. So, electronegativity electrons. So, electronegativity increases RIGHTincreases RIGHT in a period of in a period of elements.elements.

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Trends in ElectronegativityTrends in Electronegativity

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Electronegativity increases acrossa period and up a group

ElectronegativityElectronegativity

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ElectronegativityElectronegativity

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The radius increases on going down a group. The radius increases on going down a group. Because electrons are added further from the Because electrons are added further from the nucleus, there is less attraction. This is due to nucleus, there is less attraction. This is due to additional energy levels and the shielding additional energy levels and the shielding effect. Each additional energy level effect. Each additional energy level ““shieldsshields”” the electrons from being pulled in toward the the electrons from being pulled in toward the nucleus.nucleus.The radius decreases on going across a The radius decreases on going across a period.period.

The radius increases on going down a group. The radius increases on going down a group. Because electrons are added further from the Because electrons are added further from the nucleus, there is less attraction. This is due to nucleus, there is less attraction. This is due to additional energy levels and the shielding additional energy levels and the shielding effect. Each additional energy level effect. Each additional energy level ““shieldsshields”” the electrons from being pulled in toward the the electrons from being pulled in toward the nucleus.nucleus.The radius decreases on going across a The radius decreases on going across a period.period.

Atomic Atomic RadiusRadius

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Atomic RadiusAtomic RadiusAtomic RadiusAtomic RadiusThe radius The radius decreasesdecreases across a period across a period owing to increase in the positive charge owing to increase in the positive charge from the protons. from the protons. Each added electron feels a greater and Each added electron feels a greater and greater + charge because the protons are greater + charge because the protons are pulling in the same direction, whereas the pulling in the same direction, whereas the electrons are scattered.electrons are scattered.

LargeLarge SmallSmallAll values are innanometers

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Atomic RadiusAtomic Radius

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Atomic RadiusAtomic Radius

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Trends in Ion SizesTrends in Ion SizesTrends in Ion SizesTrends in Ion SizesRadius in pm

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CationsCations

Cations (positive ions) are smaller Cations (positive ions) are smaller than their corresponding atomsthan their corresponding atoms

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CATIONSCATIONS are are SMALLER SMALLER than the atoms from than the atoms from which they come.which they come.

The electron/proton attraction has gone UP The electron/proton attraction has gone UP and so the radius and so the radius DECREASES.DECREASES.

Li 0.152 nm3e and 3p

Li+, 0.078 nm

2e and 3 p

+

Ionic RadiusIonic Radius

Forming a Forming a cation.cation.

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Ionic Radius for CationsIonic Radius for CationsPositive ions or cations are smaller than the corresponding atoms.

Cations like atoms increase as one moves from top to bottom in a group.

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AnionsAnions

Anions (negative ions) are larger Anions (negative ions) are larger than their corresponding atomsthan their corresponding atoms

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Ionic Radius-AnionsIonic Radius-AnionsIonic Radius-AnionsIonic Radius-Anions

ANIONS are LARGER than the atoms from which they come.The electron/proton attraction has gone DOWN and so size INCREASES.Trends in ion sizes are the same as atom sizes.

Forming an anion.Forming an anion.

F 0.064 nm9e- and 9p+

F- 0.133 nm10 e- and 9 p+

-

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Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?

Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?

Ion SizesIon Sizes

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Ionic Radii for AnionsIonic Radii for Anions

Negative ions or anions are larger than the corresponding atoms.

Anions like atoms increase as one moves from top to bottom in a group.

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Ionic Radius for anIonic Radius for an Isoelectronic Group Isoelectronic Group

Isoelectronic ions have the same number of electrons.

The more negative an ion is the larger it is and vice versa.

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Summary of Periodic TrendsSummary of Periodic Trends

The D Block Elements

The d block elements fall between the s block and the p block.

They share common characteristics since the orbitals of d sublevel of the atom are being filled.

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The D Block ElementsThe D block elements include the transition metals. The transition metals are those d block elements with a partially filled d sublevel in one of its oxidation states.

Since the s and d sublevels are very close in energy, the d block elements show certain special characteristics including:

1. Multiple oxidation states

2. The ability to form complex ions

3. Colored compounds

4. Catalytic behavior

5. Magnetic properties.40