3l. The covalent bonding in the ethene molecule

Doc Brown's Chemistry: Chemical Bonding and structure GCSE level, IGCSE, O, IB, AS, A level US grade 9-12 level Revision Notes


Covalent bonding diagram for ETHENE covalent molecule, molecular formula C2H4

* metals \ non-metals (zig-zag line)

Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1 1H  Note that hydrogen does not readily fit into any group but is a non-metal 2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn
The covalent molecule ethene from carbon combining with hydrogen

 

(c) doc b Two atoms of carbon (2.4) combine with four atoms of hydrogen (1) to form ethene C2H4 (only the outer shell of carbon's electrons are shown).

On the right, the Lewis diagram of ethene - a simplified 'dot and cross' electronic diagram for the covalently bonded ethene molecule.

Electronically, hydrogen (1) becomes like helium (2) and carbon (2.4) becomes like neon (2.8), so ALL the hydrogen and carbon atoms effectively have full outer shells in forming the covalent bonds when the atoms share their outer electrons.

The molecule can be shown as (c) doc b (displayed formula) with one carbon = carbon double bond and four carbon – hydrogen single covalent bonds (it has a planar shape, its completely flat!, the H–C=C and H–C–H bond angles are 120o). The valency of carbon is still 4.

The ethane molecule is held together by the four strong C–H carbon–hydrogen single covalent bonds and one C=C carbon–carbon covalent double bond.

dot and cross diagram of the ethene molecule

The above diagrams are other styles of 'dot and x' electronic diagrams for ethene.

  ball and stick model of ethene

space filling model of ethene

 


Comments

Melting point of ethene -169 oC

Boiling point of ethene -104 oC

A colourless gas at room temperature, with a strong hydrocarbon odour.

 


What next?

Recommend next: The covalent bonding in the nitrogen molecule

Explaining the properties of small covalently bonded molecules

 

Sub-index for Part 3. Covalent Bonding: small molecules & properties

 

Index for ALL chemical bonding and structure notes

 

Perhaps of interest?

The basic chemistry of alkenes like ethene

 

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