Edexcel GCE AS chemistry all bonding topics essay

Essay on all parts of the 2008 edexcel chemistry syllabus. Diagrams and explained, a few typos sorry but I hope it helps :)

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  • Created on: 02-06-11 12:21
Preview of Edexcel GCE AS chemistry all bonding topics essay

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Bonds form between atoms within molecules and between the molecules themselves. The chemical
bonds that exist between atoms in molecules can be metallic, covalent (or dative covalent) and ionic
(or electrovalent). The bonds between these molecules really depend on charges of the atoms within
due to things such as electronegativity, creating London forces, dipoledipole attraction and
hydrogen bonds.
Ionic (or electrovalent) Bonds:
From the first point it needs to be clear that achieving a noble gas structure for the outer shell of
electrons is not always the most stable state to be in. Atoms form ions which attract and want to be
at the lowest energy state possible, meaning they will want to release as much energy as they can in
the first place.
Ionic substances can form giant ionic lattices that pack tightly together due to the charges. An
example would be common salt or Sodium Chloride. The opposite charges of the atoms pull them
close together with electrostatic attractions. This attraction is very strong and to overcome the
bonds a lot of energy must be put in, meaning that in general ionic substances will have relatively high
melting points. A dislocation of the arrangements leads to opposing charges being next to one
another, these will then repel making the substance very brittle and able to crack at sharp smooth
Ionic substances will conduct electricity but only when molten or in an aqueous solution as the ions
are free to move around and conduction occurs. They tend to be soluble in polar substances, as the
charges will break up the attraction within the substance but only if there is enough energy to break
the bonds.
Covalent bonds
Covalent bonds consist of a pair of electrons shared by two atoms. Atoms share the electrons to
become more stable such as Hydrogen bonding diatomically with another Hydrogen atom, sharing
their outer electron. Not all will fill 8 electrons in their outer shell, and some will have more as below
with Phosphorous Pentachloride.
Atoms join together within a molecule allowing for the overlap of electrons. As they are overlapping
none are free to move and so covalently bonding substances will not conduct electricity. The boiling
point of the substances tends to be quite low, the intermolecular forces between molecules are not
very strong (Van der Waals) and can break easily. However some substances have ionic tendencies
and have a much higher boiling point such as water.
Tom Baker Chemistry 12ST1

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The phosphorous atom has 10 electrons in its outer shell, but it is
still stable as it has formed at a lower energy state than in its ion
Dative Covalent Bonds
Dative Covalent bonds are similar to ordinary covalent bonds but differ in the way they form. A
donor which will have lone electrons pairs in its outer shell shares them with an acceptor which does
not have a full outer shell.…read more

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The larger the
electronegative difference, the greater the bond polarity will be and more electrons will be at one
Some molecules do contain dipoles but no overall net charge. This is because the central charge is
completely surrounding by opposing forces such as in Carbon
The permanent dipole interaction is similar to that of the instantaneous,
except it is ALWAYS there in addition to basic Van der Waals.…read more

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Na+ and Mg2+ have higher boiling points as it takes more energy to pull the ions apart and Mg2+ has
a greater pull on the outer electrons.…read more


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