This is the cabon isotope 612C.
The nucleus of carbon-12 has 6 protons and 6 neutrons, while the nucleus of carbon-13 has 6 protons and 7 neutrons. Both isotopes have the same number of protons, which defines them as carbon atoms, but they differ in their neutron count, leading to different atomic masses.
The number 87 when referred to francium is that element's atomic number. The most common isotope of francium is 223, which has a half-life of 22 minutes and decays by beta-negative emission into radium-223.
C14H30 is the formula and 14 carbons are there in kerosene.
A chemical formula is a combination of element symbols that shows the ratio of elements in a compound. The subscripts in the formula indicate the number of atoms of each element present in the compound.