In alkanes with three or fewer carbon atoms, a. the chains can be straight or branched.
b. usually one but sometimes more than one molecular structure is possible.
c. structural isomers exist.
d. only one molecular structure is possible.

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

→

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons

the answer is c. nacl