Memorization tricks
3 min read

The P-Block Elements

- Finding difficulties in memorizing things? Let's learn it in some easy ways.
Trends in Melting and Boiling Point of Group 15 and 16

There are so many trends in periodic table and it's almost impossible to keep all of them in mind. And exceptions makes it all the more difficult.
Melting and boiling points are two important properties of elements - and they follow a particular trend in the periodic table.
For groups 15, 16, 17 and 18 of the p-Block elements, it generally increases on moving down the group. But be a little careful when it comes to groups 15 and 16 - there are exceptions here.
To tackle these exceptions, we have come up with very simple tricks.
First, let us figure out the trend in boiling point in groups 15 and 16.
Recall the presents elements in Groups 15 and 16. Next, interchange the elements of 4th and 5th positions to get the correct order of boiling point.
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Coming to the melting point of Group 15.
Once again, recall the elements in the group and interchange the 3rd and 5th elements.
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Finally, to find out the order of melting point in Group 16, always remember to interchange the elements of the 4th and 5th positions. There! You have the correct order of melting point of group 16 elements.
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Oxoacids of Phosphorous
Oxoacids of phosphorous are many - It can unsettle anyone who is trying hard to remember the names of these oxoacids. But it will become much easier if you follow a simple trick. Remember that the name of an oxoacid is made up of three components: Prefix + Phospho + Suffix acid , the prefix can be hypo, pyro or ortho and the suffix can be ous oric To name it correctly, look at the formula of the compound and count the number of oxygen atoms. First, identify the Prefix of the compound:
  • If the number of oxygen atoms in the compound is either 2 or 6, the prefix is hypo
  • If the number of oxygen atoms is either 5 or 7, the prefix is pyro
  • if the number of oxygen atoms is either 3 or 4, the name would have the prefix ortho
The compound has two oxygen atoms - it's prefix will be Hypo according to the trick. Now, let's go on to find the suffix, once again using the number of oxygen atoms in the compound:
  • If the number is 2, 3 or 5 - the suffix is ous
  • If the number is 4, 6 or 7 - the suffix is ic
So, our compound with two oxygen atoms, will have the suffix ous The name of the compound is, therefore, Hypophosphorous acid. Try to apply the trick and write the names of a few more oxoacids of phosphorous. I have written these by applying the trick.
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You will come across many questions related to interhalogen compounds.
We know that interhalogen compounds are formed by combining two different halogens. But do the halogens combine in any specific way?
Yes! As with all things in life, they too follow some rules while combining.
If AX is the interhalogen compound, always remember that they combine in the order such that A is of lower electronegativity and X is of higher electronegativity.
To remember the order, think of LEAN MEN when you think of interhalogen compounds.
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