Helium - 4 isotope has 2 protons and 2 neutrons.
Its atomic number is 2 (the number of protons). Atomic number is the number of protons in the atom of an element and it identifies the element. All the isotopes of an element have the same atomic number (same number of protons). So, all the isotopes of hellium have 2 protons.
The number 4 that identifies the helium - 4 isotope is the mass number, i.e. the number of protons plus the number of neutron. So, helium-4 isotope has 2 protons and 2 neutrons. While, other isotopes of helium have 2 protons but different number of neutrons.
The atomic number enable us to deduce the number of electrons in an atom because the atoms are neutral, which implies that the positive and negative charge are equal. Given that the magnitude of the charge of electons and protons are equal but the sign is opposed (protons are positve and electrons are negative) the number of electrons in the atom equals the number of protonts. That is why the atomic number is also the number of electrons of the atom.
Because in caffeine the don’t use that much soluble in caffeine bis cause then there would be no flavor of caffeine but in water they do so the water doesn’t affect other to stop the solvent from getting stuck.
We know the law of conservation of mass
- It states that mass is neither formed nor destroyed in any chemical reaction.
- Mass of reactants=Mass of products.
Here
- Mg and I_2 are reactants
- MgI_2 is product with some yield.
- Mass of reactants=10+60.0=70.0g
- Mass of MgI_2=53.88g
- Mass of yield=Product-MgI_2=70-53.88=16.12g
Lets find the percentage



This is a D. combustion reaction
That is because you add O2 which is necessary for a combustion, while the results are CO2 and water. What you are missing is a ---> after the 2O2 (g)