Atomic Mass of Elements - Overview, Examples, Comparison, FAQs

Edited By Team Careers360 | Updated on Nov 08, 2024 10:50 PM IST

The atomic mass of an element can be measured by the unification of atomic mass units. Considering that a carbon-12 atom is at rest, one unified unit of atomic mass equates to one-twelfth of its mass. The atomic mass of a given element is almost equal to its mass number since protons and neutrons are responsible for the majority of its mass.

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Why do elements have different atomic masses?
The atomic mass of first 20 elements to 30 elements
Atomic mass of an element compared with its atomic number

The atomic mass of an element can be used in chemistry if the atomic mass of an element is combined with the idea of a mole: one mole of an element has a mass in grams equal to its atomic mass of elements in amu. One mole of iron atoms weighs 55.847 grams due to its atomic mass of elements of 55.847 amu. Ionic compounds and molecules can be treated in the same way.

It is calculated that a mole of sodium chloride (NaCl) would weigh 58.44 formula units (22.9897 amu for Na and 35.453 amu for Cl), which is equal to 58.44 grams. Water (H₂O) has an average mass of 18.02 amu (2x1.00797 amu for H + 15.9994 amu for O) and has an average molecular atomic weight of 18.02 grams.

Why do elements have different atomic masses?

Elements are described by their atomic mass

An atom's mass is the combined mass of all its protons. The unit is known as the unified atomic mass unit and is represented by 'u'.

As a measure of the average atomic mass of a mixture of isotopes in a given sample of an element, standard atomic atomic weight is used Periodic Table of the Element

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NCERT Solutions for Class 11 Chemistry	NCERT notes Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties
NCERT Solutions for Class 12 Chemistry	NCERT solutions for Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties
NCERT Solutions for All Subjects	NCERT Exemplar Class 11 Chemistry Solutions Chapter 3 Classification of Elements and Periodicity in Properties

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The atomic mass of first 20 elements to 30 elements

The following table contains a list of the atomic mass of first 30 elements ordered by atomic number and atomic mass.

Atomic Number	Element	Atomic Mass
1	Atomic Mass of Hydrogen	1.008
2	Atomic Mass of Helium	4.0026
3	Lithium Atomic Mass	6.94
4	Atomic Mass of Beryllium	9.0122
5	Boron Atomic Mass	10.81
6	Atomic Mass of Carbon	12.011
7	Atomic Mass of Nitrogen	14.007
8	Atomic Mass of Oxygen	15.999
9	Atomic Mass of Fluorine	18.998
10	Atomic Mass of Neon	20.180
11	Atomic Mass of Sodium	22.990
12	Atomic Mass of Magnesium	24.305
13	Atomic Mass of Aluminium	26.982
14	Atomic Mass of Silicon	28.085
15	Atomic Mass of Phosphorus	30.974
16	Atomic Mass of Sulphur	32.06
17	Atomic Mass of Chlorine	35.45
18	Atomic Mass of Argon	39.948
19	Atomic Mass of Potassium	39.098
20	Atomic Mass of Calcium	40.078
21	Atomic Mass of Scandium	44.956
22	Atomic Mass of Titanium	47.867
23	Atomic Mass of Vanadium	50.942
24	Atomic Mass of Chromium	51.996
25	Atomic Mass of Manganese	54.938
26	Atomic Mass of Iron	55.845
27	Atomic Mass of Cobalt	58.933
28	Atomic Mass of Nickel	58.693
29	Atomic Mass of Copper	63.546
30	Atomic Mass of Zinc	65.38

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The above table shows the atomic mass of all elements or atomic number of elements from 1 to 30.

To calculate a molecule's molecular mass, add the mass of each of its constituent atoms. There are several methods of finding the atomic mass of an element, but the simplest is to look it up on the periodic table.

NCERT Chemistry Notes :

Atomic mass of an element compared with its atomic number

Learn how elements differ from one another in terms of their atomic number and atomic mass now.

Atomic mass	Atomic Number
An element's atomic mass is proportional to the number of neutrons and protons that make up its nucleus.	Essentially, the nuclear number is the number of protons within the nucleus of a given element.
A particular element's average atomic weight is referred to as its average.	The number of nucleons present in an atom's nucleus is the number of nucleons in total.
The letter A is used for representing the atomic mass.	Atomic number Z is represented by the letter Z.
Element types cannot be determined by atomic mass.	A chemical element can usually be classified and identified by its atomic number.
Different isotopes of an element are classified according to their atomic masses	An element's atomic number is the same only for its isotopes.
The atomic mass unit (AMU) is always used to measure atomic mass.	For elements to be placed in a periodic table, the atomic number is simply a digit.

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Frequently Asked Questions (FAQs)

1. What is atomic mass?

Atomic mass is the mass of an atom, typically expressed in atomic mass units (amu), and it represents the average mass of all isotopes of an element, weighted by their natural abundance.

2. How is atomic mass calculated?

Atomic mass is calculated by taking the weighted average of the masses of all naturally occurring isotopes of an element, based on their relative abundance.

3. Why is the atomic mass not a whole number?

Atomic mass is not a whole number because it is an average of the masses of different isotopes, which have slightly different masses, and the natural abundances of these isotopes vary.

4. What is the difference between atomic mass and atomic number?

Atomic mass refers to the mass of an atom, while atomic number is the number of protons in the nucleus of an atom, determining its element identity.

5. Which element has the highest atomic mass?

The element with the highest atomic mass is Oganesson (Og), with an atomic mass of around 294 amu.