7.6 Molecular structure and polarity  (Page 2/27)

 Page 2 / 27

Electron-pair geometry versus molecular structure

It is important to note that electron-pair geometry around a central atom is not the same thing as its molecular structure. The electron-pair geometries shown in [link] describe all regions where electrons are located, bonds as well as lone pairs. Molecular structure describes the location of the atoms , not the electrons.

We differentiate between these two situations by naming the geometry that includes all electron pairs the electron-pair geometry    . The structure that includes only the placement of the atoms in the molecule is called the molecular structure    . The electron-pair geometries will be the same as the molecular structures when there are no lone electron pairs around the central atom, but they will be different when there are lone pairs present on the central atom.

For example, the methane molecule, CH 4 , which is the major component of natural gas, has four bonding pairs of electrons around the central carbon atom; the electron-pair geometry is tetrahedral, as is the molecular structure ( [link] ). On the other hand, the ammonia molecule, NH 3 , also has four electron pairs associated with the nitrogen atom, and thus has a tetrahedral electron-pair geometry. One of these regions, however, is a lone pair, which is not included in the molecular structure, and this lone pair influences the shape of the molecule ( [link] ).

As seen in [link] , small distortions from the ideal angles in [link] can result from differences in repulsion between various regions of electron density. VSEPR theory predicts these distortions by establishing an order of repulsions and an order of the amount of space occupied by different kinds of electron pairs. The order of electron-pair repulsions from greatest to least repulsion is:

$\text{lone pair-lone pair}>\text{lone pair-bonding pair}>\text{bonding pair-bonding pair}$

This order of repulsions determines the amount of space occupied by different regions of electrons. A lone pair of electrons occupies a larger region of space than the electrons in a triple bond; in turn, electrons in a triple bond occupy more space than those in a double bond, and so on. The order of sizes from largest to smallest is:

Questions & Answers

Why does carbonic acid don't react with metals
Aditya Reply
Why does carbonic acid don't react with metal
Aditya
Some metals will react depending on their Standard Electrode Potential. Carbonic acid is a very weak acid (i.e. a low hydrogen ion concentration) so the rate of reaction is very low.
Paul
sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
Emokiniovo Reply
a sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
Sharmin Reply
an object of weight 10N immersed in a liquid displaces a quantity of d liquid.if d liquid displaced weights 6N.determine d up thrust of the object
ugonna Reply
how human discover earth is not flat
Jason Reply
We don't fall off. If set off in any direction in a straight line and keep going. You'll end up back where you started.
Adelle
earth is spherical
Unique
Also, every other planet is spherical as that is the most energy efficient shape. gravity pulls equally on all areas. Sphere.
Adelle
what is an ion
Unique Reply
an atom that loses or gains an electron. Atoms normally have the same number of protons and electrons, therefore there is no charge as each + cancels out each -. When an atom loses an electron, it has more protons that electrons. Therefore the ion is called positive.
Adelle
When an atom gains electrons it has more of them than protons. Therefore the ion is negative. You cannot change the number of protons as this results in a different element.
Adelle
Gaining or losing electrons is based around the octet rule. 8 electrons in the outer shell is the most stable electron configuration (for the first three rows in the periodic table. After that it gets confusing so don't worry) So all atoms want to achieve this configuration.
Adelle
Wat is chemical bonding
Precious Reply
how to determine the number of atoms and the mass of zirconium, silicon, and oxygen found in 0.3384 mol of zircon4
Denisha Reply
can you please help
Badmus
what is a catalyst
William Reply
A substance that speeds up the rate of a given reaction but does not react with any reactants
Brandon
something that speeds up a chemical reaction without being used up itself. It lowers the activation energy
Adelle
something that speed up a chemical reaction without its self been used
Zainab
Faraday's first law of electrolysis state that...
Mgbachi Reply
the mass of a substance librated during electrolysis is directly proportional to the quantity of electricity passing through the electrolyte
Zainab
nice
Owolabi
greeaat
Abdul
another question
Owolabi
ys
Abdul
good
olanrewaju
gud one pls write it mathematically
Lekan
How can ionic bonds dissociate in aqueous solution
Andrew Reply
Because of the polarity of both ionic compounds and water the ionic compound will dissolve as "like dissolves like", and the molecule forms bonds with the water.
Claud
are all aqueous solutions water contained?
blossom
No, but a lot are.
Claud
it dissociate when d metal is combined wit oxygen
Lekan
I wanna understand more about isomers
Emmanuel Reply
Isomers are essentially the same molecules of one particular substance, except with different bonding points along the molecule. if you want a better example, look up xylene, p-xylene, and m-xylene. isomers are more for organic chemistry
Aaron
what is catenation
Oladuji Reply
The property of carbon to form long chain with other atom!
Lareb
hydrocarbons can be classified as..1.Aliphatic compounds 2.cyclic compounds.under aliphatic compounds there are two types saturated hydrocarbons(alkanes) and unsaturated hydrocarbons(alkenes and alkynes).
Niroshan Reply
thanks but i have also heard of aromatic hydrocarbons
emmanuel
so am kinda confused
emmanuel
how
Emmanuel
hydrocarbons are classified into 2 namely: aliphatic compound and aromatic compound
Mgbachi
aliphatic compound and aromatic compound
Mgbachi
hello i have big problems in understanding organic chemistry
emmanuel Reply
what are the main types of hydrocarbon
emmanuel
I'm not exactly sure what you mean by 'main types' but I think you should be talking about aliphatic and cyclic hydrocarbons
blossom
What's the difference?
Claud
what is the difference between atomic theory and modern atomic theory
Yakubu
Or are you referring to the types being alkane, alkene and alkyne? alkane - hydrocarbon molecule with only single bonds alkene - hydrocarbon molecule with at least 1 double bond alkyne - hydrocarbon with at least 1 triple bond. alkane least reactive, alkene in the middle alkynes most reactive
Adelle
I think that is what he is talking about
IBRAHIM

Read also:

Get the best Chemistry course in your pocket!

Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry' conversation and receive update notifications?

 By By By By By