That is not a valid formula. Mercury (I) bromide is actually Hg2Br2. Mercury is peculiar in several ways, and one of them is that the +1 mercury ion exists as a dimer instead of an isolated ion.
Silver bromide.
The 'ide' ending means the compound contains 2 elements only (in this case silver, Ag and bromine, Br).
On the other hand, an 'ate' ending means the compound also contains oxygen.
For example, sodium chloride contains sodium and chlorine, copper oxide contains copper and oxygen and sodium chlorate contains sodium, chlorine and oxygen.
Chemical formula for AgBr
Element
The formula is H2O. The name of this compound is water.
Phosphorus pentachloride is the chemical compound with the formula PCl5.
No compound has the formula PC15. However there is PCl5,which is called phosphorus pentachloride.
Chemical formula for AgBr
Silver will have a +1 and bromate is -1 so they combine in a 1:1 ratio. The formula would be AgBrO3.
Silver bromide.
AgBr is the chemical formula of silver bromide.
Compound
Element
AgBr is the chemical formula (not symbol) of silver bromide.
AgBr
The name of the compound CH4 is methane.
Silver Bromide
Phosphorus pentachloride is the chemical compound with the formula PCl5.
The formula is H2O. The name of this compound is water.