Elements and Compounds - Definition, Example, Types, Classification, FAQs

Classification of Matter

Chemistry is the study of different types and properties of matter. We see different types of components and materials all around us. It is therefore essential to classify and categorize them so that they can study, analyze and understand their characteristics easily of elements compounds, and mixtures. The matter around us can be classified as pure matter and impure matter. Those with fixed chemical composition are pure substances. A pure substance is divided into elements and compounds. Since impure substances are substances that may have different compositions and therefore do not have any fixed characteristics thus, they can't be divided into elements and compounds.

Element

A substance that cannot be broken down into simpler components using chemical methods or A substance composed of atoms with one atomic number is called an Element. An element meaning is a complete chemical substance that constitutes an entry in the modern periodic table. Elements and compounds are made up of only one type of atom and two or more elements and compounds respectively. They cannot be broken down into simpler fragments and can exist in the form of atoms or molecules. The elements are represented by symbols, issued by IUPAC. For example, Hydrogen is represented by H, Nitrogen is represented by N, and so on.

Examples of Elements

Below we have listed 10 examples of elements,

Related Topics Link

• Laws of Chemical Combination for Elements and Compounds
• Balancing Chemical Equations
• Mole Concept Basics
• Difference Between Physical and Chemical Change
• Difference Between Compound and Mixture

Types of Elements

Elements are classified into metals, non-metals, and semi-metals according to their properties.

Metals: Metals are the electro positivity elements that tend to lose electrons in order to achieve stability. Metals have physical characteristics such as hardness, high stresses, lusters, conductivity, high melting and boiling points, etc.

Examples: Iron (Fe), Sodium (Na), Calcium (Ca), Lead (Pb), etc.

Non-metals: Non-metals are the elements that tend to get electrons, i.e. they are electron-negative. They are not metals. Non-metallic physical properties include fragility, comparatively less strength of the tensile materials, brightness, non-conductivity or isolation, lower melting and boiling points, etc.

Example: Hydrogen (H), Chlorine (Cl), Iodine (I), Phosphorus (P), etc.

Metalloids: Metalloids are elements with properties between metals and nonmetals.

Example: Boron (B), Germanium (Ge), Silicon (Si), etc.

Read more :

• NCERT notes Class 11 Chemistry Chapter 1 Some basic concepts of Chemistry
• NCERT solutions for Class 11 Chemistry Chapter 1 Some basic concepts of Chemistry
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Compound

A compound is a pure substance formed when two or more different elements chemically combine in a fixed ratio by mass. The elements in a compound are held together by chemical bonds (ionic or covalent), and the compound has properties different from its constituent elements.

Key Points

• Composition is fixed (definite proportion).
• Components cannot be separated by physical methods (need chemical methods).
• Has new physical and chemical properties.

Examples of Compounds

Below we have listed 10 examples of compounds,

Types of compounds

Compounds can be categorized as ionic and covalent compounds on the basis of formation.

Ionic Compound: Between metal and non-metal, ionic compounds are formed. They are also known as electrovalent ion compounds. The metal atom is cation-forming and the non-metal atom is forming an anion. Electrons are anions.

Examples: sodium chloride, calcium oxide, etc.

Covalent compound: Between two non-metals covalent compounds are formed. It is also known as a molecular compound. The electrons are formed by the sharing of two or more nonmetals.

Example: water, carbon dioxide, methane, sugar, etc.

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Some Solved Examples

Question 1: Which of the following is known as dry ice?

1) Gaseous CO₂

2) Solid SiO₂

3) CH₄

4) (correct) Solid CO₂

Solution:

Solid CO₂ is called as dry ice.

Hence, the answer is option (4).

Question 2: Which of the following is an element?
A) $\mathrm{H}_2 \mathrm{O}$
B) NaCl
C) $\mathrm{O}_2$
D) $\mathrm{CO}_2$

Solution:

An element consists of only one type of atom. O₂ contains only oxygen atoms, so it is an element. The others are compounds made of more than one type of element.

Hence, the answer is option (3).

Question 3: Which of the following statements is true for a compound?

A) It can be separated into simpler substances by physical methods.
B) It has properties identical to its constituent elements.
C) It is formed by the chemical combination of elements in a fixed ratio.
D) It contains only one type of atom.

Solution: Compounds are chemically combined substances with fixed composition. Their properties are different from the elements that form them, and they cannot be separated by physical methods.

Hence, the answer is option (3).

Question 4: Which of the following is a compound containing both metallic and non-metallic elements?
A) $\mathrm{O}_2$
B) NaCl
C) $\mathrm{N}_2$
D) $\mathrm{H}_2$

Solution: NaCl is formed from sodium (metal) and chlorine (non-metal). O₂ and N₂ are elements, and H₂ contains only hydrogen.

Hence, the answer is option (2).

Question 5 : Which statement is true for a compound?

A. Components can be separated physically
B. Composition is variable
C. Properties are same as constituents
D. Definite chemical formula exists

Solution:

A compound is formed when two or more elements chemically combine in a fixed ratio. Therefore, every compound has a definite chemical formula (for example, $\mathrm{H}_2 \mathrm{O}, \mathrm{NaCl}$).

Hence, the answer is option (4).