How do you determine the atomic mass of an element?

How do you determine the atomic mass of an element?

I can think of only two good ways to determine the atomic mass of an element.


Most naturally-occurring elements consist of mixtures of isotopes, so you cant just add the masses of the protons and neutrons in a single atom.1. The easy wayLook up the atomic mass in the Periodic Table.Cl

(Adapted from example, the atomic mass of Cl is 35.45 u.2. The harder wayTake the weighted average of the atomic masses of the elements isotopes.In a weighted average, we multiply each value by a number representing its relative importance (its percentage as a decimal fraction).For example, chlorine consists of 75.78 chlorine-35 (atomic mass 34.97 u) and 24.22 chlorine-37 (atomic mass 36.97 u)bbAtomic Mass/u color(white)(m)bbFractional abundance color(white)(m)bbContribution/u

color(white)(mml)34.97color(white)(mmmmmmmmm) 0.7578color(white)(mmmmmmmmm) 26.50


color(white)(mmmmmmmmmmmmmmmm)Atomic mass = color(white)(mll) stackrel(———)(35.45)The atomic mass of chlorine is 35.45 u.
Please read the following information below.


To find the molar mass of an element,

all you need to have is a periodic table.The molar mass is the same thing as the atomic mass on the periodic table.For example, lets look at Chromium. (Image below)

You can identify the atomic mass right away, 52.

Therefore, the molar mass of Chromium is 52 g mol^-1