The molecular mass of a substance is the sum of the atomic masses of all the atoms present in a molecule of that substance. The atomic mass unit is the system of measurement designed to identify each individual unit of mass in atoms and molecules. Step 1: (Atomic mass of each isotope) x (%Abundance /100) 34.96885*0.7578 = 26.50 (i) The mass of any isotope of any element is expressed in relation to the carbon-12 standard. M=n+p The atomic mass (m a or m) is the mass of an atom.Although the SI unit of mass is kilogram (symbol: kg), the atomic mass is often expressed in the non-SI unit dalton (symbol: Da, or u) where 1 dalton is defined as 1 â 12 of the mass of a single carbon-12 atom, at rest. This is commonly expressed as per the international agreement in terms of a unified atomic mass unit (amu). Units of Atomic Mass. The mass of atoms is measured in terms of the atomic mass unit, which is defined to be 1 / 12 of the mass of an atom of carbon-12, or 1.660538921 × 10 â24 gram. We show mass number with letter "M". The universal mass unit, abbreviated u (sometimes amu for atomic mass unit), is defined as one-twelfth of the mass of the 12 C atom which has been defined to be exactly 12 u. The first isotope has an atomic mass of 34.96885 and has an abundance of 75.78%. If there are isotopes then, average atomic mass is the 'Sum of isotopic abundance × mass of isotope' e.g. Gram atomic mass is the atomic mass of an element expressed in grams. However, the 'm' is often expressed in unified atomic mass unit (u), which is also recommended by IUPAC. Example: Calculating the atomic mass of a given chlorine sample where two isotopes are mixed. Mass number = number of protons + number of neutrons. The second isotope has an atomic mass of 36.96590 and has an abundance of 24.22%. Many people use the terms interchangeably, but they don't actually mean the same thing. Sometimes also amu is used, which is a unit based on the mass of 16O . Find an answer to your question âExplain what is meant by the atomic mass unit (amu) ? Get an answer to your question âExplain what is meant by the atomic mass unit (amu) ? ; Monoisotopic mass is typically expressed in unified atomic mass units ( u ), also called daltons ( Da ). Atomic mass is the unit in which the mass of an atom is expressed, where one atomic mass unit is 1/12 th the mass of a carbon-12 atom. One proton or a neutron has a mass of 1 amu. The atomic mass constant, denoted m u is defined identically, giving m u = m(12 C)/12 = 1 Da.. Thus the molecular mass of each member differs by 14 atomic mass units. Atomic Mass is an extremely important concept in Chemistry. Here, the atomic weights of each atom in g/mol unit are added to get the molecular mass. n. Abbr. Atomic weight and atomic mass are two important concepts in chemistry and physics. The standard unit of atomic mass is the unified mass unit. This module shows how the mole, known as Avogadroâs number, is key to calculating quantities of atoms and molecules. Atomic mass can be calculated as: (1) Atomic mass is the average mass of an element calculated from the relative abundance of the isotopes. This has been proven wrong in certain cases: argon and calcium atoms each have an atomic mass of 40 amu. Cecilia answered on June 15, 2015. 1 Answer to WHAT IS THE UNIT OF ATOMIC MASS.PLEASE EXPLAIN WITH A EXAMPLE ... WHAT IS THE UNIT OF ATOMIC MASS.PLEASE EXPLAIN WITH A EXAMPLE Jun 15 2015 02:27 AM. An atom of sulfur-32 has a mass of $$31.972 \: \text{amu}$$. Explain atomic mass and gram atomic mass. Define atomic mass unit. Unified atomic mass unit definition: a unit of mass used to express atomic and molecular weights that is equal to one twelfth... | Meaning, pronunciation, translations and examples For example, one atom of helium-4 has a mass of 4.0026 amu. The mass of any isotope of any element is expressed in relation to the carbon-12 standard. This means that a carbon-12 atom has the atomic mass of 12 daltons. ...â in ð Chemistry if you're in doubt about the correctness of the answers or there's no answer, then try to use the smart search and find answers to the similar questions.