(1869) Dmitri Mendeleev(Russian chemist) shows a first version of the periodic table. He noticed...

•(1869) Dmitri Mendeleev(Russian chemist) shows a first version of the periodic table. •He noticed that classifying the elements by their atomic mass a periodicity in certain properties could be seen. The first table consisted of 63 elements. •Periodicity: the regular repeating of properties according to the arrangement of elements in the PT.

**Henry Mosely(British) Henry Mosely(British) discovered nuclear charges discovered nuclear charges of all known elements and of all known elements and that chemical properties of that chemical properties of

elements are related to elements are related to their atomic numbers but their atomic numbers but

not atomic weights.not atomic weights.

He stated that elements He stated that elements should be arranged in should be arranged in

order of increasing order of increasing atomic atomic numbersnumbers..

So, today’s periodic table So, today’s periodic table was formed.was formed.

In modern periodic table, In modern periodic table, elements are listed in order elements are listed in order

of increasing atomic of increasing atomic numbers.numbers.

Elements with similar Elements with similar chemical properties are chemical properties are

placed in the same vertical placed in the same vertical columns.columns.

1A:Alkali metals1A:Alkali metals2A:Alkaline earth metals2A:Alkaline earth metals

3A:Earth metals3A:Earth metals4A:Carbon Family4A:Carbon Family

5A:Nitrogen Family5A:Nitrogen Family6A:Oxygen Family6A:Oxygen Family

7A:Halogens7A:Halogens8A:Noble(Inert)gases8A:Noble(Inert)gases

GROUPS/FAMILIES:GROUPS/FAMILIES: The vertical columnsThe vertical columns Elements in the same group have Elements in the same group have -similar chemical -similar chemical

properties(exception:properties(exception:H in 1A group)H in 1A group)-Same number of valence electrons-Same number of valence electronsand orbitals.(exception:He in 8A and orbitals.(exception:He in 8A

group)group)

***For *For A A (MAIN) (MAIN) groups; # of valence groups; # of valence electrons= # of the group(except electrons= # of the group(except

He in 8A)He in 8A)

in 7A;number of valence in 7A;number of valence electrons=7electrons=7

However, we can’t say the same However, we can’t say the same thing for B groups.thing for B groups.

**Lanthanides&Actinides belong to Lanthanides&Actinides belong to 3B group(the biggest group 3B group(the biggest group

including 32 elements)including 32 elements)

PERIODS:PERIODS:

The horizontal rowsThe horizontal rows There are 7 periods There are 7 periods Valence shell determines the period Valence shell determines the period

numbernumber Each of them starts with a metal and Each of them starts with a metal and

ends with a noble gas.(except first ends with a noble gas.(except first and seventh ones)and seventh ones)

Elements in the same period have the Elements in the same period have the same # of energy levels or shells or same # of energy levels or shells or principle quantum numbers.principle quantum numbers.

PERIODIC TRENDS:PERIODIC TRENDS:1)1)ATOMIC&MASS NUMBER:ATOMIC&MASS NUMBER:

AN,MN increases

AN,MN increases

2)2)ATOMIC RADIUS:ATOMIC RADIUS:

Br Br

2r

Radius of an atom:Half the distance between the nuclei in a molecule consisting of identical

atoms.

Atomic size (volume,radius) is affected by mainly two factors in the periodic table:

1)The # of shells (as it increases, atomic volume also increases)

2)Nuclear charge(as the p+ # increases, atomic volume decreases)

Li Be B C N O F

Na

Atomic volume decreases

WHY?WHY?

K

1A 2A 3A 4A 5A7A6A

Within the same period;All the elements have the same # of shells but the p+ # increases from left to

right.Therefore,atomic radius decreases from left to right.

3)IONIZATION ENERGY:The minimum amount of energy

required to remove the most loosely bound 1 mole of e- from

a mole of gaseous atoms is called “the ionization

energy(I).”X(g) + I1 X+

(g) + e-

WARNING!!! X2(s)+I1 X+(s) + e- !!!It’s not the

IE(bec. X is a solid and molecular)

3)3)IONIZATION ENERGY:IONIZATION ENERGY:

2)g(2)g( XIX

)g(1)g( XIX

What determines What determines IEIE

The greater the nuclear The greater the nuclear charge, the greater IE.charge, the greater IE.

Greater distance from Greater distance from nucleus (atomic radius) nucleus (atomic radius) decreases IEdecreases IE

Shielding of electrons in Shielding of electrons in filled inner shellsfilled inner shells

***Because I of d block elements are irregular, rules that we talk about the IE

belong to A group elements.The variation of first ionization

energies within the same period:As the atomic volume increases, the

attraction of the nucleus on the electrons decreases.

*Ionization energies in the same period:Noble gases > nonmetals > metals

Atomic volume decreases& IE generally increases

Ionization energyIonization energy All the atoms in the same All the atoms in the same

period have the same energy period have the same energy level.level.

Same shielding.Same shielding. But, increasing nuclear But, increasing nuclear

charge.charge. So IE So IE generallygenerally increases from increases from

left to right.left to right.

***In the same period from left to right the ionization energies:

1A < 3A < 2A < 4A < 6A < 5A < 7A < 8A

irregularitiesThe variation of IE within the same

group:

Down the group, atomic volumes of elements increase and more shielding effect, same ENC.Therefore, the IE of elements decrease in the same group

from top to bottom.

Firs

t Ion

izat

ion

ener

gy

Atomic number

He

He has a greater He has a greater IE than H.IE than H.

same shielding same shielding greater nuclear greater nuclear

chargecharge

H

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li has lower IE than H

Outer electron further away

outweighs greater nuclear charge

Li

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Be has higher IE than Li

Same shielding greater nuclear

charge

Li

Be

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He B has lower IE than Be B has greater shielding greater nuclear charge 3rd e in 2nd shell is slightly

more diffuse and its electron easier to remove

Li

Be

B

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

Breaks the Breaks the pattern, because pattern, because the outer the outer electron is paired electron is paired in the 2in the 2ndnd shell shell and experiences and experiences inter-electron inter-electron repulsion.repulsion.

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Ne has a Ne has a

lower IE than lower IE than HeHe

Both are full,Both are full, Ne has more Ne has more

shieldingshielding Greater Greater

distancedistance

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Na has a lower

IE than Li Both are s1

Na has more shielding

Greater distance

Na

Firs

t Ion

izat

ion

ener

gy

Atomic number

Increases

Increases

The rare gases (He, Ne, Ar, Kr, Xe, Rn) appear at peak values of ionization energy, which reflect their chemical inertness, while the alkali metals (Li, Na, K, Rb, Cs) appear at minimum values of ionization energy, in keeping with their reactivity and ease of cation formation.

4) 4) ELECTRONEGATIVITY:ELECTRONEGATIVITY:Electronegativity is the Electronegativity is the

power of an atom to attract power of an atom to attract electron density in a electron density in a covalent bond covalent bond (Linus (Linus Pauling)Pauling)

ElectronegativityElectronegativity Electronegativity describes how Electronegativity describes how

electrons are shared in a electrons are shared in a compoundcompound

Consider the compound HClConsider the compound HCl

•The electron clouds represent where the two electrons in the HCl bond spend their time (sizes of atoms are not being shown)

•The shared electrons spend more time around Cl than H. In other words Cl is more electronegative than H.

H Cl

+ –

ElectronegativityElectronegativity

+ – 0 0

H Cl H H

ElectronegativityElectronegativityPauling’s electronegativity scale

H

2.1

He

-

Li

1.0

Be

1.5

B

2.0

C

2.5

N

3.0

O

3.5

F

4.0

Ne

-

Na

0.9

Mg

1.2

Al

1.5

Si

1.8

P

2.1

S

2.5

Cl

3.0

Ar

-

These numbers are derived from These numbers are derived from several factors including EA, IE, atomic several factors including EA, IE, atomic radiusradius

You do not need to understand where You do not need to understand where the numbers come fromthe numbers come from

You need to know that a high number You need to know that a high number means the element has a greater pull means the element has a greater pull on electronson electrons

Calculating EN differencesCalculating EN differences The first step in defining the polarity of a The first step in defining the polarity of a

bond is to calculate electronegativity bond is to calculate electronegativity difference (difference ( EN) EN)

EN = EN large - EN smallEN = EN large - EN small E.g. for NaCl, E.g. for NaCl, EN = 3.2 –0.9 = 2.3, ionic. EN = 3.2 –0.9 = 2.3, ionic.

Bigger electronegativity,Bigger electronegativity,

-Bigger tendency in gaining -Bigger tendency in gaining electrons.electrons.

SummarySummaryShielding is constantAtomic Radius decreasesIonization energy increasesElectronegativity increasesNuclear charge increases

Nu

clear

charg

e

incr

ease

sS

hie

ldin

g i

ncr

ease

sA

tom

ic r

ad

ius

incr

ease

sIo

nic

siz

e i

ncr

ease

sIo

niz

ati

on

en

erg

y d

ecr

ease

sE

lect

ron

eg

ati

vity

d

ecr

ease

s

55)METALLIC AND )METALLIC AND NONMETALLIC CHARACTER:NONMETALLIC CHARACTER:

Metals always lose electrons in compounds.The ease with losing an electron forms the metallic character of elements.Therefore, the elements with low ionization energies reflect the metallic properties well.

Tendecy in gaining electrons forms the nonmetallic character.

PROPERTIES OF METALS Conduct the elctricity in their molten and solid states. Solid at room conditions excpet Hg. Always lose electron in chemical rxns.Thus, they can

only form cations. Ductile and malleable. Have lustre appearance. Have high melting points. Cannot form compounds w/ each other. Instead, they

can only form homogeneous mixtures called “alloys.”(e.g., bronze, stel, solder, brass)

PROPERTIES OF NONMETALS

Do not conduct the electricity, except graphite(C).

Can be solid, liquid, or gas at room condtiions.

Tend to gain electrons or share electrons in their compounds.

Are brittle. Have opaque appearance.

Increasing nonmetallic character(Except 8A)

Incre

asi

ng

non

meta

llic

ch

ara

cte

r

5)Metallic and Nonmetallic activity

-Metallic activity decreases-Nonmetallic activity increases-Metallic

activity increases-Nonmetallic activity decreases

Bigger electronegativity,Bigger electronegativity,

-Bigger tendency in gaining -Bigger tendency in gaining electrons.electrons.

Which elements are the most Which elements are the most reactive metals and reactive metals and nonmetals in the periodic nonmetals in the periodic table?table?

Francium(Fr) and Cesium(Cs) Francium(Fr) and Cesium(Cs) in 1A are the most reactive in 1A are the most reactive metals.metals.

Fluorine(F) in 7A is the most Fluorine(F) in 7A is the most reactive nonmetal.reactive nonmetal.

OXIDATION STATES OF OXIDATION STATES OF ELEMENTSELEMENTS

Group

IA IIA IIIA IVA VA VIA VIIA

VIIIA

MAX(+)

+1 +2 +3 +4 +5 +6 +7 NA

MIN(-)

NA NA NA -4 -3 -2 -1 NA

Important Groups

Groups of Elements•Alkali Metals(IA)(except Fr):

–Group 1A metals –Soft, silvery colored metals that react violently with H2O to form basic solutions

- They have low melting points - They have low melting points and densities and densities due to being the due to being the largest atom in their period of largest atom in their period of the PTthe PT..

Going down the group, the Going down the group, the metals get softer, heavier metals get softer, heavier (d increases), and mp (d increases), and mp decreases due to increase decreases due to increase in atomic size.in atomic size.

•Alkali MetalsAlkali Metals(IA)(IA)(except (except Fr): Fr):

- They are the most reactive of They are the most reactive of

all the metals on the periodic all the metals on the periodic tabletable since they can easily since they can easily lose their one elose their one e..

- Their rectivity also increases Their rectivity also increases as you move down their as you move down their family.Therefore;family.Therefore; most reactive ones are: Cesium & Francium

Because the elements are very Because the elements are very reactive, they easily combine with reactive, they easily combine with water and Oxygen.Therefore, most water and Oxygen.Therefore, most of these elements are not found of these elements are not found freely in nature.That is why they are freely in nature.That is why they are stored in oil in a bottle in the stored in oil in a bottle in the laboratory in order to prevent any laboratory in order to prevent any reaction with Oxygen.reaction with Oxygen.

They tarnish (lose lustre) rapidly They tarnish (lose lustre) rapidly when exposed to the air.when exposed to the air.

Chemical Reactions of Alkali Chemical Reactions of Alkali MetalsMetals

Li KNa

Alkali Metal Family

•They give caharacteristic colour in the flame(chemical peoperty).

Chemical Reactions of Chemical Reactions of Alkali MetalsAlkali Metals

Reaction with oxygen,Reaction with oxygen, React with oxygen to produces oxides.React with oxygen to produces oxides.

44Li(s) + OLi(s) + O22(g) (g) 22LiLi22O(s)O(s)

Chemical Reactions of Chemical Reactions of Alkali MetalsAlkali Metals

Reaction with halogensReaction with halogensReaction with halogens produces saltsReaction with halogens produces salts

2Na(s) + Cl2Na(s) + Cl22(g)(g) 2NaCl(s)2NaCl(s)2K(s) + Br2K(s) + Br22(g)(g) 2KBr(s)2KBr(s)2Cs(s) + l2Cs(s) + l22(g)(g) 2CsI(s)2CsI(s)

Exist as diatomic molecules in which Exist as diatomic molecules in which atoms are joined by a single cov. atoms are joined by a single cov. bond.bond.

The elements in this group are The elements in this group are referred to as Halogens because referred to as Halogens because they produce salts when combined they produce salts when combined with alkali metalswith alkali metals (e.g. (e.g.NaCl)NaCl).these .these salts are usually white & soluble in salts are usually white & soluble in water.water.

•HALOGENS(VIIA)HALOGENS(VIIA) except Atexcept At::

They are all very reactiveThey are all very reactive and quite and quite electronegativeelectronegative nonmetals nonmetals. The ease . The ease w/ which they gain electrons w/ which they gain electrons decreases going down the group.decreases going down the group.

Halogens tend to be Halogens tend to be lessless reactive as reactive as you move down the group.you move down the group.FlourineFlourine is is the most reactive Halogen and the most reactive Halogen and combines with other elements very combines with other elements very readily.readily.

Oxidizing power decreases down the Oxidizing power decreases down the group.group.


Most are Poisonous Most are Poisonous .. When Fluorine combines with Na to When Fluorine combines with Na to

form NaF,it is an effective cavity form NaF,it is an effective cavity fighter that is added to fighter that is added to toothpastes.toothpastes.

Chlorine is a great bacteria fighter Chlorine is a great bacteria fighter so it is used in swimming pools and so it is used in swimming pools and household cleaning agents.household cleaning agents.

Iodine is also useful for eliminating Iodine is also useful for eliminating bacteria.Since it is not as reactive bacteria.Since it is not as reactive as Chlorine, it can be used on as Chlorine, it can be used on humans.humans.

Going down the group, their physical state Going down the group, their physical state varies at room temp & pressure depending varies at room temp & pressure depending on the Van Der Waals force strength on the Van Der Waals force strength present between molecules since the present between molecules since the molecules have different molecular mass molecules have different molecular mass values.values.

FF22, Cl, Cl22 -- -- gas gas BrBr22 --- --- liquid liquid II22 -- -- solid, forms a purple gas on heating. solid, forms a purple gas on heating. They all need an electron to become stable, They all need an electron to become stable,

thus form negative ionsthus form negative ions


Are slightly soluble in water as they Are slightly soluble in water as they are non-polar molecules.are non-polar molecules.

Concentrated solutions of chlorine-Concentrated solutions of chlorine- green tingegreen tinge

Solutions of bromine-Solutions of bromine- darken from darken from yellow through orange to brown as the yellow through orange to brown as the concentration increases.concentration increases.

Iodine dissolved in non-polar solvents Iodine dissolved in non-polar solvents like hexane--like hexane--violet solution.violet solution.

Iodine dissolved in polar solvents like Iodine dissolved in polar solvents like water & ethanol--water & ethanol--brown solution.brown solution.


Halogens dissociate slightly in aqueous Halogens dissociate slightly in aqueous solutions, forming an acidic solution:solutions, forming an acidic solution:

ClCl22(aq) + H(aq) + H22O(l) O(l) H H++ (aq)+ Cl (aq)+ Cl--(aq) + (aq) + HOCl(aq)HOCl(aq)

HOCl(hypochlorous acid): weak acid, reacts as HOCl(hypochlorous acid): weak acid, reacts as an oxidant since it donates its one oxygen.It an oxidant since it donates its one oxygen.It oxidises colored dyes to colorless products.oxidises colored dyes to colorless products.

HOCl turns blue litmus paper into red, and HOCl turns blue litmus paper into red, and then make it colorless. Therefore, HOCl and then make it colorless. Therefore, HOCl and OClOCl-- are used in bleaches.They are also toxic are used in bleaches.They are also toxic to microbes.to microbes.


Are slightly soluble in water as they Are slightly soluble in water as they are non-polar molecules.are non-polar molecules.


They are stable and will They are stable and will rarelyrarely react with any other elements.react with any other elements.

They are gaseous at room They are gaseous at room conditions.conditions.

Each nobel gas has 8 valence Each nobel gas has 8 valence electrons,except He.It has 2 electrons,except He.It has 2 valence electrons.valence electrons.

•NOBEL NOBEL (Inert)(Inert)GASES(VIIIA):GASES(VIIIA):

The Nobel gases are used in neon The Nobel gases are used in neon

signs.Each nobel gas glows a signs.Each nobel gas glows a different colour when electricity different colour when electricity is passed through it.For instance, is passed through it.For instance, Helium glows pink,neon glows Helium glows pink,neon glows orange-red, and argon glows orange-red, and argon glows purple.It isn’t just neon in those purple.It isn’t just neon in those signs!signs!

Jellyfish lamps made with noble gases

Displacement reactions of Displacement reactions of HalogensHalogens

A more reactive halogen A more reactive halogen is capable of replacing is capable of replacing less reactive one from less reactive one from

its solutionits solution

ClCl22 reacts with Br reacts with Br-- and I and I-- ClCl22(aq)(aq) + 2Br + 2Br--(aq)(aq) 2Cl 2Cl--(aq)(aq) + +

BrBr22(l)(l)

ClCl22(aq)(aq) + 2I + 2I--(aq)(aq) 2Cl 2Cl--(aq)(aq) + I + I22(s)(s)

BrBr22 reacts with I- reacts with I-BrBr22(aq)(aq) + 2I + 2I--(aq)(aq) 2Br 2Br--(aq)(aq) + I + I22(s)(s)

II22 non-reactive non-reactive with halide ions with halide ions

76

The common insoluble halides (ions of The common insoluble halides (ions of halogens) are those of Pb and Ag.halogens) are those of Pb and Ag.

PbIPbI2 2 ---- is a bright yellow colored, can is a bright yellow colored, can be used as a test for iodide ion.be used as a test for iodide ion.

Look at P. 77 Look at P. 77

& 78 for the colors of & 78 for the colors of

halogens and tests halogens and tests

of halide ions.of halide ions.


Oxides of period 3 elementsOxides of period 3 elements

Metallic Oxides in Period 3Metallic Oxides in Period 3

Sodium oxide: NaSodium oxide: Na22OO ionicionic

Magnesium oxide: MgOMagnesium oxide: MgO ionicionic

Aluminum oxide: AlAluminum oxide: Al22OO33 ionicionic

Metalloid oxide in Period 3Metalloid oxide in Period 3

Silicon dioxide: SiOSilicon dioxide: SiO22 covalentcovalent

Nonmetallic oxides in Period 3Nonmetallic oxides in Period 3

Tetraphosphorus decoxide: PTetraphosphorus decoxide: P44OO1010 covalentcovalent

Sulfur trioxide: SOSulfur trioxide: SO33 covalentcovalent

Dichlorine heptoxide: ClDichlorine heptoxide: Cl22OO77 covalentcovalent

78

Discuss the changes in nature, from Discuss the changes in nature, from ionic to covalent and from basic to ionic to covalent and from basic to

acidic, of the oxides across period 3.acidic, of the oxides across period 3.

Acidic/BasicAcidic/BasicMetallic oxides in Period 3 are basicMetallic oxides in Period 3 are basicSodium oxide: Sodium oxide: NaNa22O + HO + H22O O 2 NaOH 2 NaOH

basicbasicMagnesium oxide: Magnesium oxide: MgO + HMgO + H22O O Mg(OH) Mg(OH)22 basicbasic

Net ionic eqn: ONet ionic eqn: O2-2- + H + H22O O 2 OH 2 OH--

Aluminum oxide: Aluminum oxide: AlAl22OO33 + 6HCl + 6HCl 2 AlCl 2 AlCl33+ 3H+ 3H22O O amphotericamphoteric

AlAl22OO33 +2 NaOH + 3H +2 NaOH + 3H22O O 2NaAl(OH) 2NaAl(OH)44

79

Oxides of period 3 Oxides of period 3 elementselements

Metalloid oxide in Period 3 is acidicMetalloid oxide in Period 3 is acidicSilicon dioxide:Silicon dioxide: SiOSiO22 + H + H22O O H H22SiOSiO33 acidicacidic

(silicic acid) (silicic acid)

Nonmetallic oxides in Period 3 are acidicNonmetallic oxides in Period 3 are acidicTetraphosphorus decoxide: PTetraphosphorus decoxide: P44OO1010 + 6H + 6H22O O 4H 4H33POPO44 acidicacidicSulfur trioxide: Sulfur trioxide: SOSO33 + H + H22O O H H22SOSO44

acidicacidicDichlorine heptoxide: Dichlorine heptoxide: ClCl22OO77 + H + H22O O 2HClO 2HClO44 acidicacidicArgon does not form an oxideArgon does not form an oxide

Look at!!Look at!!

P.80P.80

References References

http://www.youtube.com/watch?http://www.youtube.com/watch?v=m55kgyApYrY(Date of accession: v=m55kgyApYrY(Date of accession: 14/11/2011)14/11/2011)

(1869) Dmitri Mendeleev(Russian chemist) shows a first version of the periodic table. He noticed...

Documents

Transcript of (1869) Dmitri Mendeleev(Russian chemist) shows a first version of the periodic table. He noticed...