Atomic Structure(Lesson )

8/8/2019 Atomic Structure(Lesson )

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ATOMIC STRUCTUREATOMIC STRUCTURE

What is an ATOM?What is an ATOM?

oo All matter is made from atomsAll matter is made from atoms

ooThe configuration of the atom :The configuration of the atom :

ProtonsProtonsNeutronsNeutrons

ElectronsElectrons

ooThe Atom is the basic buildingThe Atom is the basic buildingblock of everything around usblock of everything around us


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Subatomic particleSubatomic particle

The atoms Protons and Neutrons are in theThe atoms Protons and Neutrons are in theNucleusNucleus Protons and neutrons have almost exactly the sameProtons and neutrons have almost exactly the same

mass.mass.

ProtonsProtons are much larger and heavier than electronsare much larger and heavier than electrons..

NeutronsNeutrons are large and heavy like protons; howeverare large and heavy like protons; howeverneutrons have no electrical charge.neutrons have no electrical charge.

The atoms Electrons orbit around the nucleus atThe atoms Electrons orbit around the nucleus atdifferent levels, called shellsdifferent levels, called shells A shell is sometimes called an orbital or energy level.A shell is sometimes called an orbital or energy level.

Shells are areas that surround the center of an atom.Shells are areas that surround the center of an atom.


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yy ElectronsElectrons are tiny, very light particles that have a negative electricalare tiny, very light particles that have a negative electrical

charge (charge (--))

yy

Electrons have a mass that is about 1/1835 the mass of a proton.Electrons have a mass that is about 1/1835 the mass of a proton.yy The electron is constantly spinning around the center of theThe electron is constantly spinning around the center of the

atom (called the nucleus).atom (called the nucleus).

yy In actuality, the electron is a wave that surrounds the nucleus ofIn actuality, the electron is a wave that surrounds the nucleus of

an atom like a cloud.an atom like a cloud.

Hydrogen: a proton surrounded by an electron cloud


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SubatomicSubatomic

particleparticle

Mass (kg)Mass (kg) Charge (C)Charge (C) RelativeRelative

chargecharge

protonproton 1.672 x 101.672 x 10--2727 1.672 x 101.672 x 10--2727 +1+1

neutronneutron 1.675 x 101.675 x 10--2727 00 00

electronelectron 0.910 x 100.910 x 10--3030 1.672 x 101.672 x 10--2727 --11


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yyExampleExample

yy The atom above, made up of one protonThe atom above, made up of one proton

and one electronand one electron

yy The proton and electron stay together,The proton and electron stay together,just like two magnets.just like two magnets.

A Hydrogen Atom


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Stable configurationStable configuration

Stable elements have equal numbers ofStable elements have equal numbers of ElectronsElectrons

ProtonsProtons NeutronsNeutrons

Stable elements have a neutral chargeStable elements have a neutral charge

1 Electron (1 Electron (--) plus) plus 1 Proton (+) plus1 Proton (+) plus

1 Neutron (0) =1 Neutron (0) =

NO CHARGENO CHARGE


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Atomic number And atomicAtomic number And atomic

massmass

As you add electrons, protons and neutrons, the size of the atomAs you add electrons, protons and neutrons, the size of the atomincreases.increases.

We can measure an atom's size in two ways: using the atomic numberWe can measure an atom's size in two ways: using the atomic number(Z) or using the atomic mass (A, also known as the mass number).(Z) or using the atomic mass (A, also known as the mass number).

Z= no. of proton in the elementZ= no. of proton in the element

For hydrogen the atomic number, Z, is equal to 1.For hydrogen the atomic number, Z, is equal to 1. For helium Z = 2.For helium Z = 2.

Z also tells you the number of electrons in the neutral atom.Z also tells you the number of electrons in the neutral atom.

A= Z + N (neutron)A= Z + N (neutron)

Therefore, the atomic mass, A, of hydrogen is 1.Therefore, the atomic mass, A, of hydrogen is 1. For helium A = 4.For helium A = 4.


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a.m.ua.m.u

For hydrogen the atomic mass is 1.00797. When we hearFor hydrogen the atomic mass is 1.00797. When we hearthe term atomic mass we think of the mass of an atom.the term atomic mass we think of the mass of an atom.For example the mass of a hydrogen atom is 1.6726 x 10For example the mass of a hydrogen atom is 1.6726 x 10--24 grams. The two numbers are different!24 grams. The two numbers are different!

a.m.u is a relative mass to a particular carbon atom.a.m.u is a relative mass to a particular carbon atom. The carbon atom selected is the carbon atom with 6The carbon atom selected is the carbon atom with 6

protons, 6 electrons and 6 neutrons.protons, 6 electrons and 6 neutrons.

1 a.m.u = 1/12 of atomic mass isotope carbon 121 a.m.u = 1/12 of atomic mass isotope carbon 12

1 amu = 1.6598 x 101 amu = 1.6598 x 10--2727kgkg

1 mole of substance= 6.023x101 mole of substance= 6.023x10--2323 atoms/moleculesatoms/molecules 1 a.m.u/atom or molecule = 1 g/mol1 a.m.u/atom or molecule = 1 g/mol

E.g platiniumE.g platinium --= 195.08 amu/atom or 195.08 g/mol= 195.08 amu/atom or 195.08 g/mol


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Isotopes and isoton (isobar)Isotopes and isoton (isobar)

IsotopesIsotopes-- atoms of the same elements with diff. atomic masses ( dif.atoms of the same elements with diff. atomic masses ( dif.No. of Neutron).No. of Neutron).

For example, an isotope of hydrogenFor example, an isotope of hydrogen

Isotopes of carbon,Isotopes of carbon, C , C, CC , C, C

Isoton/isobar: Diff. elements with same atomic massIsoton/isobar: Diff. elements with same atomic mass

E.g argonE.g argon--40 (18p +22 n) and calcium40 (18p +22 n) and calcium --40 (20 p +20n)40 (20 p +20n)

Hydrogen

Atomic Mass = 1

Atomic Number = 1

Deuterium

Atomic Mass = 2

Atomic Number = 1

6

12 13 14

6 6


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Electron configuration of theElectron configuration of the

elementselements

electron configurationelectron configuration is the arrangement ofis the arrangement ofelectronselectrons in anin an atomatom,, moleculemolecule or other bodyor other body

Electrons are on the shells around the nucleus.Electrons are on the shells around the nucleus.

Each shell has a nameEach shell has a name

The first shell is kThe first shell is k

Followed by l, m, n, o, p & qFollowed by l, m, n, o, p & q


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Shells hold only a limited number of electronsShells hold only a limited number of electrons

Different shells hold different numbersDifferent shells hold different numbers

K holds only 2 electronsK holds only 2 electrons

L holds 8 electronsL holds 8 electrons

M holds up to 18 electronsM holds up to 18 electrons

Each shell (energy level) consist of subshellEach shell (energy level) consist of subshell

(sublevel).(sublevel). Each type of sublevel holds a different orbitals.Each type of sublevel holds a different orbitals.

An orbital is a space that can be occupied by up toAn orbital is a space that can be occupied by up to

two electronstwo electrons


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The number of available electron states in some of the electronThe number of available electron states in some of the electron

shells and subshellsshells and subshells

PrincipalPrincipal

QuantumQuantum

number, nnumber, n

ShellShell

DesignationDesignation

SubshellsSubshells Number of Number of

statesstates

Number of electronNumber of electron

Per subshellPer subshell Per shellPer shell

11 KK ss 11 22 22

22 LL ss 11 22 88

pp 33 66

33 MM ss 11 22 1818

pp 33 66

dd 55 1010

44 NN ss 11 22 3232

pp 33 66

dd 55 1010

ff 77 1414


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Atomic Bonding in solidsAtomic Bonding in solids

Three types of primary or chemical bondThree types of primary or chemical bondare found in solidsare found in solids

IonicIonic

Covalent inter atomic bondingCovalent inter atomic bonding MetallicMetallic

Secondary BondingSecondary Bonding Van der WaalsVan der Waals

Hydrogen BondingHydrogen Bonding


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Ionic BondingIonic Bonding

Electron are transferred to form a bondElectron are transferred to form a bond

Often found in compounds composed ofOften found in compounds composed of

electropositive elements (metals) andelectropositive elements (metals) and

electronegative elements (non metals)electronegative elements (non metals)

Na valance

+1

Cl valance -1


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Ionic Bonding GeneralIonic Bonding General

CharacteristicsCharacteristics Bonding Energy 150Bonding Energy 150--370 Kcal/mol370 Kcal/mol

Nondirectional BondNondirectional Bond-- strength of bond equal instrength of bond equal in

all directionsall directions Low electrical conductivityLow electrical conductivity-- entire ion mustentire ion must

move to conduct electricitymove to conduct electricity

Transparent, brittle, high melting temperatureTransparent, brittle, high melting temperature

ExamplesExamples-- NaCl 183 Kcal/mol, LiF 240NaCl 183 Kcal/mol, LiF 240

Kcal/molKcal/mol


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Covalent BondingCovalent Bonding

Electrons are shared to form a bondElectrons are shared to form a bond


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Covalent Bonding GeneralCovalent Bonding General

CharacteristicsCharacteristics

Bonding energy 75Bonding energy 75--300 Kcal/mol300 Kcal/mol

Covalent bonding most frequently occursCovalent bonding most frequently occurs

between atoms with similarbetween atoms with similarelectronegativitieselectronegativities.. Directional bondDirectional bond--strength of bond is not equalstrength of bond is not equal

in all directionsin all directions

Low electrical conductivityLow electrical conductivity

Very hard, high melting temperatureVery hard, high melting temperature Examples Si 84 Kcal/mol, GaAs 75 Kcal/mol,Examples Si 84 Kcal/mol, GaAs 75 Kcal/mol,

Diamond 170 Kcal/molDiamond 170 Kcal/mol


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Metallic BondingMetallic Bonding

Founds in metalsFounds in metals

and their alloysand their alloys


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Metallic Bonding GeneralMetallic Bonding General

CharacteristicsCharacteristics

Bonding energy 25Bonding energy 25--200 Kcal/mol200 Kcal/mol

Nondirectional BondNondirectional Bond--strength of bond is equal instrength of bond is equal in

all directionsall directions

Good electrical conductivityGood electrical conductivity--cloud electron arecloud electron are

free to move to conduct electricityfree to move to conduct electricity

Ductile, opaqueDuctile, opaque

Examples Na 26 Kcal/mol, Al 74 Kcal/mol, Cu 81Examples Na 26 Kcal/mol, Al 74 Kcal/mol, Cu 81Kcal/molKcal/mol

It involves theIt involves the delocalizeddelocalized sharing of freesharing of free

electronselectrons among a lattice of metal atoms.among a lattice of metal atoms.


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Secondary BondingSecondary Bonding

Van der Waals BondingVan der Waals Bonding

Weak secondary bond (< 10 Kcal/mol)Weak secondary bond (< 10 Kcal/mol)

Often bonding force between moleculesOften bonding force between molecules

ExampleExample-- PVC can be deformed by breakingPVC can be deformed by breakingVan der Waals bonds between moleculesVan der Waals bonds between molecules

Hydrogen BondingHydrogen Bonding

Special type of secondary bond betweenSpecial type of secondary bond between

some molecules containing Hsome molecules containing H

ExampleExample bonds between molecules ofbonds between molecules ofwaterwater


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moleculesmolecules

molecule is considered the smallestmolecule is considered the smallest particleparticle ofofa purea pure chemical substancechemical substance that still retains itsthat still retains itscompositioncomposition and chemical properties.and chemical properties.

Most common molecules are bound togetherMost common molecules are bound together

by strong covalent bondsby strong covalent bonds i.e Fi.e F22, O, O22, H, H22 (diatomic molecules) or H(diatomic molecules) or H22O, COO, CO22

(host of compounds)(host of compounds)

The smallest molecule is theThe smallest molecule is the hydrogenhydrogen

moleculemolecule

Atomic Structure(Lesson )

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