i dont understand polarity of atoms

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i dont understand how to figure out bond polarities or the topic bonding i dont get can someone please help me

Posted Mon 25th March, 2013 @ 13:42 by WeTheKings

2 Answers

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download these notes and look at the bonding section


Answered Tue 26th March, 2013 @ 18:12 by Agent006
Edited by Agent006 on Tue 26th March, 2013 @ 18:13
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different elements have different electronegativities. This means the power with which they attract electrons. So highly electronegative elements attract electrons strongly - you could say they have a high affinity for electrons.

So say you have to elements, fluorine and hydrogen bonding together. fluorine is the most highly electronegative element there is with a relative value on the Pauling Scale of 4.0. hydrogen isn't the lowest but it is lower than fluorine. It's value is 2.1.. Metals have lower electronegativities than nonmetals in general. The values are the strength with which they attract electrons.

When they bond, they will share the bonding pair of electrons. However, due to the fact that fluorine is so much more electronegative than magnesium it attracts the electrons in the bonding pair. This means that the electrons move closer to the fluorine. Hence there will be more positive charge at the hydrogen end of the bond and it will be more negative at the other end. Hence poles have been made since they behave differently from each other (like the poles of a magnet). This is called a polar covalent bond.

If hydrogen was swapped for magnesium, then the electronegativity difference would be even greater. Hence the electrons would move even closer to fluorine. In fact, they would move over so far, that the magnesium would pretty much lose all control over the electrons, and ions would form. This would make ionic bonding.

If magnesium was swapped for fluorine, then there would be two fluorines in the bond. They would have the same electronegativity. Hence you would get no difference in electronegativity, and the electrons would be shared equally. That means that a nonpolar covalent bond would form. The bond is classed as nonpolar for anything up to an electroengativity difference of about 0.5.

Above 0.5 to about 1.7 the bonding is called polar covalent and anything above that is ionic. These are only rough numbers, and some compounds may have a lower electronegativity difference than 1.7. However due to the fact that they have more ionic properties they would be classed as ionic.

Answered Fri 29th March, 2013 @ 07:30 by Tilly - Team GR