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Periodic table. Electron configuration of carbon atoms and molecules. . John Summerscales. Fundamental particles in atom. Atomic number = number of protons for balanced charge (in atom) = number of electrons value is characteristic of a specific element

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Periodic table. Electron configuration of carbon atoms and molecules.

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Periodic table electron configuration of carbon atoms and molecules

Periodic table.Electron configuration of carbon atoms and molecules.

John Summerscales


Fundamental particles in atom

Fundamental particles in atom

  • Atomic number = number of protons

    • for balanced charge (in atom) = number of electrons

    • value is characteristic of a specific element

  • Atomic weight = number of (protons + neutrons)

    • can have partial values as isotopes have different numbers of neutrons and different proportions


The atom simple model

The atom (simple model)

If K=1, L=2, M=3, N=4,

then at each level there are 2n2 electrons:

n=1 gives 2 electrons

n=2 gives 8 electrons

n=3 gives 18 electrons

n=4 gives 32 electrons

K L M N


The atom simple model1

The atom (simple model)

If n = shell number - 1,

then each shell has 2(2n+1) additional electrons:

n=0 gives 2 electrons (s-block)

n=1 gives 6 electrons (p-block)

n=2 gives 10 electrons (d-block)

n=3 gives 14 electrons (f-block)

nucleus (protons and neutrons)

level 1 = 2

level 2 = 2+6 = 8

level 3 = 2+6+10 = 18

level 4 = 2+6+10+14 =32


The periodic table

The Periodic Table

Periodic table of the Elements

s-block

p-block

d-block

f-block


Inert gases

Inert gases

Fibres - glass: B, O, Al, Si

aramid: H, C, N, O

Resins - H, C, N, O

Periodic table of the Elements

This column has a full electron shell- the most stable configuration


Ionic bonding

Ionic bonding

Periodic table of the Elements

This column lose one electron to become X+

This column lose two electrons to become X2+

This column lose three electrons to become X3+


Ionic bonding1

Ionic bonding

Periodic table of the Elements

This column gains one electron to become X-

This column gains two electrons to become X2-

This column gains three electrons to become X3-


Carbon and si ge sn pb

Carbon (and Si, Ge, Sn, Pb)

Periodic table of the Elements

This column could become either X4+ or X4- ??


Carbon 4 or 4

Carbon 4+ or 4- ??

  • In practice,

    • six protons holding three electrons> strong force/electron (difficult to remove 4th e-)

    • six protons holding ten electrons> weak force/electron (difficult to retain 10th e-)

  • so, carbon shares electrons

    > covalent bonding

  • one bond ... is ... two shared electrons


Carbon covalent bonding

Carbon - covalent bonding

  • carbon has 4 electrons in the outer shell

    needs four electrons to fill shell

  • can share with 2, 3 or 4 other atoms

    • 4 other atoms = 4 x single (σ) bonds

    • 3 other atoms = 3 x σ and 1 x double (π) bond

    • 2 other atoms = two σ and two π bonds

      - 1 x single and 1 x triple (2π) bonds

  • but ....


Carbon electron orbitals

Carbon - electron orbitals

  • electron shells divide into electron orbitals

    • each has up to two electrons of opposite spin

    • electrons enter empty orbitals first

    • at level 2 of Periodic Table, maximum of:

      • 2 electrons in a spherical orbital

      • 2 electrons in a dumbbell orbit on x-axis

      • 2 electrons in a dumbbell orbit on y-axis

      • 2 electrons in a dumbbell orbit on z-axis


Electron orbitals

Electron orbitals

1s 2s2px2py

Note: the orbitals are not drawn to scale.

They are probabilities of finding an electron.The pz orbital is normal to the plane of this image.


Electron orbitals 2s 2p x 2p y 2p z

Electron orbitals (2s 2px 2py 2pz)

y

x

z


Electron orbitals p x p y p z

Electron orbitals (px, py, pz)

Animation


Electron configurations

Electron configurations

Periodic table of the Elements

  • H1s1

  • He1s2

  • Li1s2 2s1

  • Be1s2 2s2

  • B1s2 2s2 2p1

  • C1s2 2s2 2p2

  • N1s2 2s2 2p3

  • O1s2 2s2 2p4

  • F1s2 2s2 2p5

  • Ne1s2 2s2 2p6

2p1 = px1

2p2 = px1 py1

2p3 = px1 py1 pz1

2p4 = px2 py1 pz1

2p5 = px2 py2 pz1

2p6 = px2 py2 pz2


Methane ch 4

Methane (CH4)

  • carbon bonded to four hydrogen atoms

  • if each H bonds to a different electron orbitalthe resulting molecule is asymmetric

  • symmetrical molecules have lowest energyand are thus the most stable form

  • so (2s + 2px +2py + 2pz) reorganise tofour hybrid sp3 orbitals (think s1p3 !!)oriented along each line from theapex to the centre of a tetrahedron


Ch 4 tetrahedron

CH4 tetrahedron

  • Pyramid with a triangular base

  • carbon nucleus at centre

  • hydrogen at each apex

  • sp3 orbital on each line

    from apex to base centre


Electron orbitals sp 3 hybrid molecular orbital

Electron orbitals (sp3 hybrid molecular orbital)

y

x

forward behind plane forward


Electron orbitals sp 3 hybrid molecular orbital1

Electron orbitals (sp3 hybrid molecular orbital)

Animation


Add a methylene group ch 2

add a methylene group -CH2-

  • MethaneCH4generic CnH2n+2

  • Ethane C2H6

  • PropaneC3H8

  • ButaneC4H10

  • PentaneC5H12

  • HexaneC6H14

  • Heptanec7H16

  • OctaneC8H18

  • ...paraffins ... polyethylene


With one double bond

... with one double bond:

  • Methenen/ageneric CnH2n

  • Ethene C2H4a.k.a. ethylene

  • PropeneC3H6a.k.a. propylene

  • ButeneC4H8a.k.a. butylene

  • PenteneC5H10

  • HexeneC6H12

  • Heptenec7H14

  • OcteneC8H16

  • etcetera ....


With one triple bond

... with one triple bond:

  • Methynen/ageneric CnH2n-2

  • Ethyne C2H2a.k.a. acetylene

  • PropyneC3H4

  • ButyneC4H6

  • PentyneC5H8

  • HexyneC6H10

  • Heptynec7H12

  • OctyneC8H14

  • etcetera ....


Sp 2 hybrid orbital

sp2 hybrid orbital

  • 2s + 2px + 2py hybridise to 3 x sp2 orbitals

  • 2pz orbital remains and forms double bond

    < plan view (excl. pz)

    side view >

pz


Double bond c c

Double bond (C=C)

π (1e-)

σ (2e-)

π (1e-)

half of double (π) bond electrons above atom centres

centres single (σ) bond on line of atom centres

half of double (π) bond electrons below atom centres

Triple bond (C=C) has π orbitalsabove, below, in front and behind the σ bond


Consider and bonds as springs

Consider σ and πbonds as springs

compression

tension

torsion


Hybrid orbitals summary

Hybrid orbitals - summary

  • sp3 bonds to 4 other atoms4σ (single) bondsbond angle = 109° 28’ (tetrahedral molecule)

  • sp2 bonds to 3 other atoms3σ and 1πbondbond angle = 120° (triangular molecule)1σand1πbond = the double bond (i.e. 1+1 = 2)

  • sp bonds to 2 other atoms2σ and 2πbondsbond angle = 180° (linear molecule)1σand2πbonds = the triple bond (i.e. 1+2 = 3)


Benzene c 6 h 6 cyclohextriene

Benzene (C6H6 - cyclohextriene)

  • ring of six carbon atomsignore H atoms to give C at each cornertri-ene is three double bondssymmetry results in hexagonal moleculesymmetry gives lowest energy so stable molecule


Benzene kekul resonance

Benzene (Kekulé resonance)

  • left molecule is same as right molecule but upside down

  • double bonds constantly switch positions

  • change is so fast thatupper 3 electrons appear as a single ring lower 3 electrons appear as a single ring


Benzene ring

Benzene ring

  • delocalised (conjugated) electrons

C-C bond length 1.54 Å

C:C bond in benzene 1.39 Å

C=C bond length 1.33 Å


Graphite e in plane 1000 gpa

Graphite (E in-plane ~ 1000 GPa)


Periodic table electron configuration of carbon atoms and molecules

Chemical bond typeand chemical bond densityeach determine materialstiffness/strengthand chemical durability

Conclusion:


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