Difference between Elements and Atoms is that Elements are made from atoms and atoms are the smallest part of elements. Elements are the simplest form of any substance and Atoms are the simplest unit of matter. An element cannot be further broken down by chemical reactions into simpler substances. Elements are made of atoms that have the same atomic number i.e. the nucleus contains the same number of protons.
Also read: Periodic Classification of Elements
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Key Terms: Elements, Atoms, Atomic Mass of Elements, Symbols of Elements, a.m.u
Difference Between Elements and Atoms
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Major differences between the two are as follows:
| Elements | Atoms |
|---|---|
| It is the simplest form of a substance. An element cannot be broken down into simpler particles. | It is part of an element. |
| It is composed of only one type of atom, which has the same atomic number. | Atoms are made up of neutrons, electrons and protons. |
| Elements combine through chemical reactions and form molecules/chemical compounds. | Atoms can also combine and form molecules. |
| Elements are big and heavy. | Atoms are very small; billions of atoms combined would barely be as thick as a sheet of paper. |
| The total number of elements is 118. | There are 92 kinds of atoms. |
| The term element is used more often in chemistry; in the periodic table. | The term atom is used more often in physics, in chemistry it is used for atomic mass or number. |
Atomic Mass
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- Dalton’s atomic theory proposed the concept of atomic mass. According to this, each element had a characteristic atomic mass.
- The theory explained the law of constant proportions which eventually led to the measuring of atomic mass by scientists.
- They determined relative atomic masses through the compounds formed and laws of chemical combinations.
- For instance, carbon monoxide compound (CO) is formed by combining 3g of carbon with 4g of oxygen.
- The unit of atomic mass is ‘u’.
What is Atom?
Read More: Group 16 Elements
Atomic Mass of Elements
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- Hydrogen: 1
- Carbon: 12
- Nitrogen: 14
- Oxygen: 16
- Sodium: 23
- Magnesium: 24
- Sulphur: 32
- Chlorine: 35.5
- Calcium: 40
Atomic Mass
Read More: Group 18 Elements
Symbols of Elemets
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Symbols of elements have been tabulated below:
| Element | Symbol | Element | Symbol |
|---|---|---|---|
| Aluminium Al | Al | Gold | Au |
| Copper | Cu | Potassium | K |
| Nitrogen | N | Boron | B |
| Argon | Ar | Hydrogen | H |
| Fluorine | F | Silicon | Si |
| Oxygen | O | Bromine | Br |
| Barium | Ba | Iodine | I |
| Silver | Ag | Calcium | Ca |
| Iron | Fe | Sodium | Na |
| Carbon | C | Lead | Pb |
| Sulphur | S | Chlorine | Cl |
| Magnesium | Mg | Uranium | U |
| Cobalt | Co | Neon | Ne |
| Zinc | Zn |
Read More: Boron Family
Things to Remember
- Atom is the smallest part of an element and cannot exist independently.
- In an element, atoms are identical in mass and chemical properties.
- Different elements have atoms of different properties and masses.
- In a compound, the kind of atoms and relative number is constant.
- The constituent elements and the number of atoms of each combining element are shown in its chemical formula.
- A molecule is a group of two or more atoms, chemically bonded together by attractive forces.
- A substance that cannot be decomposed into simpler substances is known as an element. All matter is composed of elements, it is a pure substance made up of one type of atom.
- Atoms having the same number of protons i.e. 6 make up the carbon element. Gold, copper, silver, nitrogen and oxygen are some other examples of elements.
- 20% of the 118 known elements are synthetically prepared in a laboratory and do not exist in nature. Two or more elements combine to form a compound.
Explore More: Atoms And Molecules
Sample Questions
Ques. Name a non-metal that is tetratomic. (1 Mark) [CBSE 2012 Short Answer Question]
Ans. It is phosphorus that is tetratomic and exists as a molecule.
Ques. An element has valency 3. What is the formula of its oxide? (1 Mark) [CBSE 2012 Short Answer Question]
Ans. Oxygen’s valency is 2 while element E is 3. The formula of its oxide is E2O3.
Ques. What is the relation between given mass, molar mass and the number of moles? (1 Mark) [CBSE 2013 Short Answer Question]
Ans. The number of moles is equal to mass/molar mass.
Ques. What are the categories of elements? (2 Marks)
Ans. Elements are of three categories that are characterized by their properties. Most of the elements are metals whereas a few are nonmetals and semimetals. Most of the elements in the periodic table are metals which include transition, alkali, alkaline earth metals, etc.
Few metals in the periodic table (on the right-hand side) are non-metals which include oxygen, hydrogen, nitrogen, sulphur, carbon, etc. Silicon, Boron, Germanium, Polonium, etc. are metalloids.
Ques. What are polyatomic ions? (2 Marks)
Ans. A group of atoms carrying a positive or a negative charge; a cluster of atoms that act as ions is a polyatomic ion. For example, hydroxide ion (OH -), nitrate ion (NO−3). They consist of two or more atoms that are bound together. It is a covalently bonded set, also known as a molecular ion. Unlike a molecule that has a zero charge; it behaves as a single unit that has a net charge that is not zero. Due to the presence of two or more atoms, they have a complicated internal structure.
Ques. What are the two postulates of Dalton’s atomic theory? (3 Marks)
Ans. Postulates of Dalton’s atomic theory are:
- Law of conservation of mass- total mass of products is equal to the total mass of the reactants.
- Law of constant proportions- In a pure chemical compound, the same elements are combined in a definite proportion by mass.
Atoms cannot be destroyed or created; it is the smallest unit of matter. Atoms of the same element are similar in mass and shape but differ from atoms of other elements.
Ques. Describe an activity to demonstrate the law of conservation of mass. (3 Marks) [CBSE 2011]
Ans. In a graduated cylinder, prepare a 10% solution of barium chloride in water; add more water to touch the 100ml mark. Take some portion of this solution in a conical flask. Similarly, prepare a 10% solution of sodium sulphate and take a portion of it in a glass tube.
Cork the flask and weigh it. Shake it for mixing the reactants; to form products. Barium sulphate is the white precipitate and sodium chloride is water-soluble. Weigh the flask again, you will notice no change. This verifies that the mass of reactants is the same as that of products.
Ques. What is the atomicity of an element? State two examples. (3 Marks) [CBSE 2013]
Ans. The number of atoms present in one molecule of the element is the atomicity of an element.
Molecular mass/ atomic mass = Atomicity of an element
For example,
Atomicity of oxygen in O2 is 2
O2 represents oxygen
16 is the atomic mass of oxygen
2 x 16= 32 is the molecular mass of oxygen
Molecular mass/ atomic mass= Atomicity= 32/16= 2
Similarly, the Atomicity of oxygen in O3 is 3
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