1. Formula: C2H4
The formula for covalent compound is C2H4 is because there is 2 carbon atoms, and 4 hydrogen atoms.
Name: Ethylene
The naming of Ethylene: the system of hydrocarbon nomenclature was proposed by August Wilhelm von Hofmann in which the suffixes ane, ene, ine, one, and une are used to distinguish the hydro carbons with 0, 2 ,4 ,6 , and 8 lesser hydrogens than their parent alkane. Our chemical formula has 2 carbon atoms so we use the prefix of ethane, eth, and ene as our suffix due to the hydrogren.
2. Name: Carbon Monoxide
Naming: You don't name the first element with mono but rather the 2nd element and add ide as the suffix since it is an anion.
3. Formula: N2S5
There are 2 nitrogen atoms and 5 sulfide atoms. Hence, di means two and penta stands for five. Also, N means nitrogen and S means sulfide.
4. Formula: PCI3
There is one phosphorous atom and 3 chlorine atoms, since there is 3 chlorine atoms, we would use tetra and then add ide as the suffix since chlorine is an anion.