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Elements and Compounds are similar concepts in chemistry. There is a very subtle difference between elements and compounds. Elements are pure substances composed of only one type of atom. Whereas, compounds are substances formed by two or more different types of elements that are united chemically in fixed proportions.
Also read: Class 9 Science Chapter 2 Is Matter Around Us Pure?
| Table of Content |
Key Takeaways: Elements, compounds, atoms, protons, electrons, neutrons, mixtures, matter.
What are Elements?
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| An element is defined as a pure substance made up of atoms with no charge or atoms with an equal number of protons and electrons in them. |
This definition states that an element is made up of the basic fundamental property of matter called atoms. Now, atoms can be of different types. The number of protons and electrons can vary from each element. But whatever the number of electrons or protons, the elements always have an equal number of protons and electrons in them. Since the elements are pure, they can not be simplified into simpler forms or can’t be broken down. If so, we get atoms themselves.
There are about 118 elements that are known to us. Out of all the 118 elements, 94 of them are naturally occurring. That is we can find these 94 elements in different parts of nature- air, water, fire, earth, etc. The rest of the elements are man-made. These 118 elements are grouped or neatly arranged in a periodic table. In the beginning, these elements were grouped or arranged based on their ATOMIC MASSES. But due to different properties and anomalies like isotopes and isobars, the arrangement or grouping is now done by atomic numbers.
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Types of Elements
The elements are categorized depending upon their groups into either metallic or non-metallic. Metallic is further classified into Main Group Metals, Transition Metals, and f-block metals. These are again further divided, depending upon their properties.
Examples of Elements
Elements exist in their simplest form that cannot be broken down further. So, elements can exist in the form of ions, atoms, isotopes, and molecules.
- An example of an element is a Nitrogen atom(N), Nitrogen gas (N2), Nitrogen ion(N3–) and Nitrogen isotopes (Nitrogen-13, Nitrogen-14, and Nitrogen-15).
Examples of some commonly used elements along with their chemical symbols:
| Name of the element | Chemical symbol |
|---|---|
| Hydrogen | (H) |
| Boron | (B) |
| Carbon | (C) |
| Silicon | (Si) |
| Sodium | (Na) |
| Lead | (Pb) |
| Platinum | (Pt) |
What are Compounds?
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| Compounds are the combinations of two or more elements with strong or weak attractive forces between them. |
There are 2 types of bonds: covalent bonds and ionic bonds.
| A covalent bond is a chemical bond wherein sharing of a pair of electrons occurs. |
These bonds are extremely strong forces. The pairs of electrons that are shared are called ‘ bonding electrons’ or ‘shared electrons’.
| An Ionic bond is a chemical bond and involves electrostatic forces of attraction between oppositely charged ions. |
IONS are atoms in which the number of electrons is not equal to the number of protons. If the number of protons is more than the number of electrons, the ion is positively charged and thus called ‘CATION’. If the number of electrons is more than that of protons, the negatively charged ions are formed and these negatively charged electrons are called ‘ANION’. With the help of these bonds, 2 or more elements form and join together to form a compound. While some bonds occur naturally, man-made compounds can also exist.
Types Of Compounds
Compounds can be divided into two types namely, molecular compounds, and salts. In molecular compounds, the atom binds to each other through covalent bonds. In salts, it remains together with ionic bonds. These are the two types of bonds of which every compound is made.
Example Of Compounds
- Examples of compounds comprise water (H2O), Hydrogen Peroxide (H2O2), etc. You could see water’s chemical formula, it says it has 2 atoms of Hydrogen combined with 1 atom of oxygen and in hydrogen peroxide, it has 2 atoms of hydrogen and two atoms of oxygen.
- Similarly, an example of salt would be table salt (NaCl) which has 1 atom of sodium and one atom of chlorine.
Examples of some commonly used compounds and their molecular formula:
| Compound Name | Compound Formula |
|---|---|
| Alcohol | C2H6O |
| Acetic Acid | C2H4O2 |
| Sulphuric Acid | H2SO4 |
| Ammonia | NH3 |
| Methane | CH4 |
| Nitrous oxide | N2O |
| Salt | NaCl |
Difference Between Elements And Compounds
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| Basis of Difference | Element | Compound |
|---|---|---|
| Building Blocks | Element is formed by pure atoms with no charge on them. | Compounds are formed by the mixing of two or more atoms. |
| Divisibility | Atoms can not be further broken down. | Compounds can be broken down to get elements. |
| Count | There are 118 elements present today. | The number of compounds can not be decided as there are many possibilities of bonds forming. |
| Organisation | The elements are organized or arranged in a systematic periodic table. | No such tables are present for compound organisation. |
| Bonding | There are no ionic or covalent bonds present between atoms. | Ionic or covalent bonds are required for the formation of compounds. |
| Charge | Atoms always have neutral charges. | Ions formation occurs for the formation of bonds. |
| Availability | Elements are abundantly available in nature. | While some compounds are freely available in nature, most of them are man-made. |
| Representation | An element is represented using symbols( alphabetic). | A compound is represented using a formula. |
| Number of Atoms | The number of atoms is the same throughout. | Heteromolecules are present. |
| Identification | Can be identified by their specific atomic numbers. | Can be predicted or interpreted by their chemical formula and bonds. |
| Existence | Can exist in nature freely as atoms or molecules. | Exists only as the complete compound and can not exist in their ionic forms. |
| Properties | The properties of elements are specific to that particular element. | The properties of compounds are different from the elements that make the compound up. |
| Separation | The elements can be separated by chemical or physical methods. | Separation of compounds can occur only by chemical methods as the bonds between molecules are stronger. |
| Smallest Unit | The smallest particle of an element is the atom. | The smallest particle of a compound is the molecule. |
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Things to Remember
- Elements are species of atoms that have the same number of protons in their atomic nuclei.
- Compounds can be referred to as substances consisting of 2 or more different types of elements in a fixed ratio of their atoms.
- When atoms of the same element have different numbers of neutrons, they are called isotopes.
- The elements can be divided depending upon their groups as either metallic or non-metallic.
- An atom contains three important parts, namely - A PROTON, AN ELECTRON, AND A NEUTRON.
- The atomic mass is defined as the approximate number of protons and neutrons or also called ‘nucleons’ of an atom in a chemical element.
- The atomic number is defined as the number of protons and electrons present in an atom.
Sample Questions
Ques: Define element and compound. (2 marks)
Ans: An element is a naturally occurring or man-made substance that is pure, made up of atoms of no charge.
A compound is the combination of two or more elements and also does not contain any charge on it.
Ques: Differentiate between elements and compounds with respect to molecules. (4 marks)
Ans:
ELEMENTS:
- All molecules in elements are homogeneous. That is, all elements are made up of the same type of atoms.
- The molecules that make up an element always have a neutral charge. This means that all molecules or atoms in an element have an equal number of protons and electrons.
COMPOUNDS:
- The molecules that make up compounds are heterogeneous. Since the compound contains a combination of elements, all atoms or molecules may or may not be the same.
- The molecules may have different charges on them. That is, ions with opposite charges are present to form covalent bonds or ionic bonds.
Ques: Write down the examples of elements and compounds. (2 marks)
Ans: ELEMENTS: There are 118 elements in nature.
Some of them are: Hydrogen, Oxygen, Nitrogen, Sodium, Phosphorus, Calcium, etc
COMPOUNDS: The number of compounds is infinite as there can be many combinations possible. Some of the examples for compounds include:
Water, Sodium bicarbonate, Sodium chloride, Barium Sulphate, Silver chloride, etc.
Ques: Write an example of a compound. (1 mark)
Ans: A compound is a material that is composed of two or more components. Water, carbon dioxide and table salt are some examples of compounds.
Ques: How can compounds be classified? (2 marks)
Ans: Compounds can be divided into two types namely, molecular compounds, and salts. In molecular compounds, the atom binds to each other through covalent bonds. In salts, it remains together with ionic bonds. These are the two types of bonds of which every compound is made.
Ques: Is pure substance an element? (2 marks)
Ans: A component is referred to as a single material that can not be divided into various types of substances. Carbon, oxygen, hydrogen, gold, silver and iron are examples of elements. Every element consists of just one atom form.
Ques: What are the two classifications of mixtures? (1 mark)
Ans: Mixtures can be classified into two major groups: homogeneous and heterogeneous. A homogeneous mixture is one in which the entire composition of its elements is combined evenly.
Ques: What are an atom element compound and mixture? (3 marks)
Ans: The same number of protons and electrons would be found in a single atom and most atoms contain a minimum of as many neutrons as protons. An element is referred to as a material completely formed from one form of an atom. A composite is a material consisting of chemically connected two or more separate elements.
Ques: With reference to elements, define the term ‘molecule’. Give two examples each of a monoatomic, diatomic and polyatomic molecule. (4 marks)
Ans: Atoms of the same element or different elements combine in order to form a molecule. It is the smallest particle of a substance – which can normally exist independently and can retain, the physical and chemical properties of the substance.
Examples
Monoatomic molecule: Metals – Na, Mg, etc.
Diatomic molecule: H2, O2, N2.
Polyatomic molecule: O3, P4.
Ques: State five different characteristics of compounds. (5 marks)
Ans: Five characteristics of a compound are as follows:
(a) Components in a compound have a definite proportion.
(b) Compound is always homogenous, that is identical composition.
(c) Particles in a compound are of one kind.
(d) Compounds have a definite set of properties.
(e) Elements in the compound do not retain their original properties.
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