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# Atomic Mass and Atomic Weight

Atomic mass and Atomic weight are two different types of measurements that scientists use to identify the number of protons, neutrons, and electrons in an atom. Atomic weight is more accurate because it takes into account the different masses of the three particles. The mass-to-mass ratio is then calculated by dividing each individual particle’s relative weight by their sum. Atomic mass and Atomic weight are two ways scientists measure the number of protons, neutrons, and electrons in an atom. They’re not exactly interchangeable terms; Atomic mass includes only protons and neutrons while Atomic weight also includes the electron mass in its calculation.

### What is Atomic Mass?

Atomic mass is the total number of protons, neutrons and electrons in an atom.

In its most basic form, it takes the mass of each particle and adds them up. This sum equals either the mass of a single atom or the total amount of atoms in a given element.

### Significance of Atomic Mass

Atomic mass calculations are used to identify the type and quantity of atoms in a material; for example, to determine the number of atoms in a sample or element. The atomic mass is an indication of the total number of protons, neutrons and electrons in the nucleus because like charges repel each other so having more particles causes there to be a larger nucleus. If you were to increase the number of protons, neutrons or electrons you’d be increasing the atomic mass since it is just a sum.

### What is Atomic Weight?

Atomic weight is the relative weight of a given element to another element based on how much they have in common. It’s calculated by dividing each particle’s atomic mass by their respective masses.

To understand this concept, let’s take an example using Gold (Au) as our reference element: The atomic weight of gold ranges from 195.8 to 196.966 daltons. Its atomic mass, however, is one of the most stable in existence. Its measured value of 197.2 daltons means it has a very high ratio of protons to neutrons, and very few electrons per atom. Thus, one gold atom is heavier than one of many other elements (such as sulphur), but lighter than another element (such as bismuth). Note that this definition is specific to a single element so it will not change no matter how many other elements are added to a sample – even if that sample contains multiple elements and compounds.

### Significance of Atomic Weight

The atomic weight is an indication of the relative weight of a given element in relation to other elements. It is also the only universally accepted measurement in chemistry and will remain constant even when multiple elements are combined; this makes it useful in comparing samples that have been synthesized by various methods.

To understand why atomic weight and mass differ, let’s look at Gold (Au) again: This element has a measured Atomic Weight of 196.966 daltons and its Atomic Mass is 197.2 daltons, which means its ratio of protons to neutrons is 1:1 while its ratio of protons to electrons is 2:1 – this makes it very stable and also heavier than most other elements.

### Atomic Mass and Weight: Difference

1. Atomic Mass is the total number of protons, neutrons and electrons in an atom. Atomic Weight is the relative weight of a given element in relation to other elements.
2. Atomic Mass does not change no matter what else is added to a sample (this includes compounds), but Atomic weight can be determined by adding more elements or compounds.
3. Atoms don’t attract each other as strongly as they do with electrons, so the ratio of protons to neutrons will stay constant even if you add more atoms – which means that its ratio of atomic mass compared to atomic weight will remain constant even if you add more elements or compounds; this makes it useful in comparing samples that have been synthesized by various methods.
4. Atomic weight is a more accurate measurement since it takes into account the mass of each particle individually.
5. Atomic Mass is sometimes referred to as ‘relative atomic mass’ or ‘molecular weight’.
6. Atomic Weight can be estimated by multiplying masses of elements; however, this does not give the actual value of its atomic weight because each element has different masses – the only way to get an accurate measurement of its atomic weight is by actually calculating it.
7. The difference between mass and weight is that mass refers to an object’s resistance while weight refers to an object’s gravitational pull; this means that a 70 kg person will feel heavier than a 70 kg brick.
8. Atomic Mass is measured in daltons, amu, u or g/mol. If it’s measured in g/mol then the numerical value will be followed by an ‘u’ (ie: H: 1.008 u); if it’s measured in amu then the numerical value will be followed by an ‘amu’ (ie: Be: 4.004134 amu).
9. The mass of an atom can vary depending on how many neutrons and electrons it has – when it’s calculated using the most stable isotope of that element.
10. The atomic mass is a measurement of the sum total of the nucleus’s protons, neutrons and electrons while Atomic Weight is the relative weight of a given element in relation to other elements.

### Conclusion

Both Atomic Mass and Atomic Weight are important in chemistry because they are two different ways of calculating the number of protons, neutrons and electrons an atom has. They both use the same principle; however, they don’t exactly have the same meaning. Atomic Mass is just a way of measuring the number of protons, neutrons and electrons in an atom while Atomic Weight is a relative measurement that determines how much like another element it is.

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Get answers to the most common queries related to the IIT JEE Examination Preparation.

## What's the difference between atomic mass and atomic number?

Answer: Atomic number is the number of protons in an atom, while Atomic mass is the sum of protons, neutrons...Read full

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Answer: You divide each element’s mass into its respective element. For example, Carbon-12 h...Read full

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Answer: The relative atomic mass (also called atomic weight, molar mass or average atomic mass) is ...Read full