Because chlorine atoms occur as two isotopes: 35Cl and 37Cl. The first accounts for 75.76% of chlorine and the second for the rest so the [weighted] average mass is(75.76*35 + 24.24*37)/100 = 35.48 = 35.5, approx.
The average atomic mass of an element is the average of the atomic masses of its isotopes (that is a weighted average). You have to take into account the abundance of each isotope when they do your averaging.
What is weighted average atomic number
The average atomic mass is the ratio of the average mass of one atom of an element to one twelfth of the mass of an atom of carbon-12. It is, the mass of an atom of the substance, rescaled so that carbon-12 would have a mass of 12.
The atomic mass of chlorine is not 355 it is 35.5 (approx). So, if the molecular mass is 71 then the atomicity is 71/35.5 = 2.
35.45
Chlorine is a non metal element. Chlorine atomic mass is 35.453.
The atomic mass of 35.45 is an average value. Chlorine has two principal stable isotopes, 35Cl (75.78%) and 37Cl (24.22%). Thus we account for the proportion of each isotope and derive an average atomic mass for chlorine. Atomic mass = 0.7578(35) + 0.2422(37) = 35.45
the atomic mass of chlorine is 35.453
The average atomic mass is weighted by the most common isotopes and their relative abundance.
Chlorine is a meta element. Atomic mass of it is 35.
Chlorine is a non metal element. Atomic mass of it is 35.45.
Atomic Mass: 35.453
Chlorine has an atomic mass of 35.453.
The relative atomic mass of chlorine is 35.5. The two main isotopes are chlorine-35 and chlorine-37.
The atomic mass for chlorine (Cl) is 17
Chlorine does not have atomic mass 5, so it cannot be "the only element that has a 5 atomic mass".