Question

About valency books say following things:

1- Valency is combining capacity of an atom with number of hydrogen atoms or double of oxygen atoms with which the atom combines. Doubt A: what is valency of C in C2H2 and CO? 2- Valency is number of electrons gained, lost or shared by atom to complete its octate. Doubts B: in CO carbon shares 2 electrons and gains 2 electrons. There are triple bond between C and O. Should valency of carbon be 2 or 3 or 4? Then 3- Electrovalency = number of charge on an ion. And 4- Covalency = number of shared electrons. Then books say that 5- For an element covalency and electrovalency are equal. Then books say that 6- Valency of carbon is 4. Now when I see carbon monoxide (CO), I am not able to figure out valency of carbon or oxygen. Then comes oxidation number (hypothetical charge), which seems to be similar to electrovalency (actual charge), but still some online sources say these are different things. Doubt C: Why do we calculate oxidation number? How is it different from electrovalency? Is the only difference hypothetical and actual?

Answer 1

The valency of carbon in C2H2 and CO is 4. The oxidation number is calculated to determine the hypothetical charge of an element, which is different from the actual charge or electrovalency. Both these numbers are used to understand the behavior and bonding of elements

Step-by-step explanation:

Oxygen has six valence electrons and carbon has four; therefore in CO32- there will be a total of 22 valence electrons, plus two additional electrons from the 2- charge.

The central atom in our structure will be carbon (it is to the left of oxygen in the periodic table). Next, we draw the carbon (our central atom) with its' four electrons and add the additional two electrons from the charge.

The three oxygens are placed around the carbon and the electrons are arranged to form the three covalent bonds. Next, the 18 remaining electrons are distributed around the oxygens so that they all have a full octet.

The carbon, however, is only surrounded by six electrons. To remedy this, we move one electron pair in to form a double bond to one of the oxygen atoms. Finally, the polyatomic ion is enclosed in brackets with the charge as a superscript.