how to calculate formal charge and i will teach you super easy tray firstly let me teach you my personal mnemonic to remember this trick i always write we break down here we stands for valence electrons b stands for bonds and d stands for dots let me repeat it v stands for valence electrons b stands for bonds d stands for dots now let me teach you the super easy trick firstly i write hcnov we know that the valency of hydrogen is 1 the valency of carbon is 4 the valency of nitrogen is 5 the valencia of oxygen is 6 the valencia fluorine is 7. now consider this molecule calculate the formal charge of every atom in this molecule firstly i find the formal charge of carbon atom we use the trach we break down and then we minus them here we stands for the valency of carbon b strands for the bonds of carbon and d stands for the dots we know that the variance of carbon is 4 minus secondly i count the total number of bonds formed by the carbon atom one two three so carbon forms three bonds in this molecule minus then i count the total dots present on carbon atom one two so there are two dots present on this carbon atom after calculation i get minus -1 so the formal charge on this carbon atom is -1 now coming to the nitrogen atom again we use the trick we break down and then we minus them we know that the valency of nitrogen atom is 5 minus icon the total number of bonds formed by the nitrogen atom one two three so nitrogen atom also form three bonds minus no icon the total dots present on nitrogen atom one two so there are two dots present on nitrogen atom after calculation i get zero so the formal charge on nitrogen atom is zero remember that we cannot write zero as a formal charge thus using this trig we can easily calculate formal charge on any atom and a molecule now consider this molecule of hydronium firstly let me calculate the formal charge of oxygen atom we use the trig we break down we know that the valency of oxygen atom is 6 minus this oxygen atom forms three bonds minus there are two dots present on this oxygen atom after calculation i get positive one so the formal charge on this oxygen atom is positive one now coming to the first hydrogen atom we know that the valency of hydrogen atom is one minus this hydrogen atom forms one bond minus there are no dots present on this hydrogen atom so we get zero thus the formal charge on this hydrogen atom is zero secondly consider this hydrogen atom we know that the valency of hydrogen atom is one minus this hydrogen atom also form one bond minus there are no dots present on this hydrogen atom so we get zero thus the formal charge on this hydrogen atom is also zero now coming to the third hydrogen atom the valency of hydrogen atom is one minus it forms one bond minus there are no dots present on this hydrogen atom so we get zero thus the formal charge on this hydrogen atom is also zero secondly consider this molecule of carbon dioxide gas let me calculate the formal charge on carbon atom we use the trick we break down we know that the valency of carbon is 4 minus this carbon atom forms 4 bonds in this molecule minus there is no dot present on this carbon atom so i get zero thus the formal charge on this carbon atom is zero now coming to this oxygen atom we know that the valency of oxygen atom is six minus this oxygen atom forms two bonds with the carbon minus there are four dots present on this oxygen atom so i get zero thus the formal charge on this oxygen atom is zero now coming to this oxygen atom we know that the valency of oxygen is six minus this oxygen atom also forms two bonds minus there are four dots present on this oxygen atom so we get zero thus the formal charge on this oxygen atom is also zero finally consider this molecule of ozone i will calculate the formal charge on each oxygen atom that this is first oxygen atom this is second oxygen atom and this is the third oxygen atom now coming to the first oxygen atom we use the trig we break down we know that the valency of oxygen atom is six minus this oxygen atom forms three bonds minus there are two dots present on this oxygen atom so i get positive one thus formal charge on this oxygen atom is positive one now coming to the second oxygen atom the valency of oxygen is six minus this oxygen atom forms two bonds minus there are four dots present on this oxygen atom so i get zero plus the formal charge on this oxygen atom is zero now coming to the third oxygen atom the valency of oxygen atom is six minus this oxygen atom forms only one bond minus there are six dots present on this oxygen atom so i get minus one thus the formal charge of this oxygen atom is minus one therefore using this trig we can easily calculate the formal charge of any atom in a molecule