Since it talks about the number of particles, we would need the Avogadro's number which is an empirical value equal to 6.022×10²³ particles/mole. Therefore, to determine the number of particles, such as molecules, just multiple the number of moles to the Avogadro's number:
Number of Br₂ molecules = 0.42 mol *6.022×10²³ molecules/mole = 2.53×10²³ molecules
Metal ore has other elements in it as well. Also sediment and stone might cover the ore. We don't want to have a phone with sediment on it do we? thus these few reasons are why.
In general chemistry, isotopes are a group of substances that belong to the same element. An element is characterized in the periodic table by their atomic number, which is the number of protons in an atom. Therefore, these substances have the same atomic numbers, but differ in mass numbers. Mass number is the sum of the number of protons and neutrons in the nucleus of an atom.
To determine the atomic weight of an element, you take the average weight of all the existent isotopes of that said element. The calculation would require to multiply the exact mass of the isotope to its abundance. Then, sum them all up.
Atomic weight = 98(0.18) + 112(0.82)
Atomic weight = 109.48 amu
