how to find how many single,double and triple bonds are present in molecule?
Answers
The number of bonds for a neutral atom is equal to the number of electrons in the full valence shell (2 or 8 electrons) minus the number of valence electrons. This method works because each covalent bond that an atom forms adds another electron to an atoms valence shell without changing its charge.
Answer:
Your first step should be to analyse the compound. For example, if the compound is carbon, you know it always has a valence of four, so, if it has a formula C2H4 (ethylene) it obviously has a double bond. There are difficulties here because benzene C6H6 can be considered to have 6 1.5 C-C bonds, being aromatic.
A second step is to look at its structure. Double bonds are traditionally shorter than single bonds; triple bonds shorter still. Covalent bonds do have typical lengths, nevertheless you can still have problems.
A third step is to consider reactivity. For example, if you have a C=C double bond, you can add, say, bromine to it Thus C2H4 gives C2H4Br2, and by adding two bromine atoms you know you have one double bond. Again, benzene becomes an awkward molecule, but because of this, you know benzene does not have double bonds in the traditional sense
Unfortunately, when you get into some complicated organometallic systems, it is not always clear what the bond structure is, and there are some debates from time to time, but to make sense of these, I am afraid a somewhat deeper knowledge of chemistry is required.