[Chemistry Class Notes] on Elements and Compounds Pdf for Exam

Chemistry is the study of various kinds of matter and its properties. All around us, we see various kinds of substances and materials. It is therefore imperative to classify and categorize them so that their properties can be easily studied, analyzed, and understood. The matter around us can be categorized into pure matter and impure matter. Pure substances are the ones that have a fixed chemical composition. Impure substances are the ones that can have varying compositions, and as such do not exhibit a fixed set of properties.

 

Pure substances can further be classified into elements and compounds. Impure substances are also called mixtures. Depending on their composition, they can further be classified into homogeneous and heterogeneous.

 

 

What is an Element?

In chemistry, an element is a substance that cannot be further broken down into a simpler substance by using common chemical methods. All matter is fundamentally composed of elements. To date, more than 119 elements have been discovered and many more are in the process of being discovered. Every element has a fixed place in the periodic table, depending on its properties.

 

The smallest entity of an element is called an atom. Atoms are highly unstable, therefore do not exist independently. They always tend to combine with other elements in order to attain stability. To represent an atom of an element, we use symbols. Every element has a fixed symbol. Some commonly used symbols of elements are listed below.

 

Commonly Used Symbols of Elements

 

Classification of Elements

Depending on the properties, elements can be classified into metals, nonmetals, and metalloids.

 

Metals are the elements that have the tendency of losing electrons in order to gain stability, that is, they exhibit electropositivity. The physical properties of metals include hardness, high tensile strength, luster, conductivity, high melting and boiling points, etc.

 

Examples include sodium, potassium, iron, calcium, magnesium, lead, tin, etc.

 

Non-metals are the elements that have the tendency of gaining electrons in order to gain stability, that is, they exhibit electronegativity. The physical properties of non-metals include brittleness, comparatively lower tensile strength, non-luster, non-conductivity or insulation, lower melting and boiling points, etc.

 

Examples include hydrogen, helium, chlorine, iodine, sulfur, phosphorus oxygen, etc.

 

Metalloids are the elements that have properties that are in between those of metals and nonmetals.

 

Examples include boron, silicon, arsenic, antimony, germanium, etc.

 

What are Compounds?

A compound is a pure substance that is formed by the chemical combination of two or more elements in a fixed proportion by mass. Compound formation always takes place as a result of a chemical reaction. Therefore, a compound does not exhibit the properties of its constituent elements. On breaking down the compound, the smallest entity so obtained is called a molecule of the compound.

 

One molecule of a compound is represented by its chemical formula. The formula of a compound is the statement of the composition of that particular compound in which the symbols represent the elements that are present in it while the subscripts show the number of atoms of each element. A molecule is stable and has an independent existence.

 

The molecular formulae of some commonly used compounds are listed below:

 

Molecular Formulae of Some Commonly Used Compounds

 

Classification of Compounds

On the basis of the formation, compounds can be classified as ionic compounds and covalent compounds.

 

Ionic compounds are formed between a metal and a non-metal. They are also called electrovalent compounds as they involve ions. The metal atom loses electrons to form a cation, and the non-metal atom gains the electron to form an anion.

 

Examples include sodium chloride, magnesium iodide, calcium oxide, etc. 

 

Covalent compounds are formed between two non-metals. They are also called molecular compounds. They are formed as a result of the sharing of electrons between two or more non-metals.

 

Examples include water, carbon dioxide, methane, sugar, etc.

About the Chapter

Elements and compounds form the foundation of chemistry. Without these, two chemistry is far more incomplete. This basic foundation of chemistry is introduced to students in the ninth grade and as discussed briefly in chapter 2 called Is Matter around us pure? Just stop explaining in-depth about what are the types of mixtures around us and what are the things that form a mixture. As we all know that most of the matter that surrounds us is a mixture of two or more components for example minerals, soil, seawater all these are types of mixtures.

This chapter and the concept of elements and compounds are prescribed by the Central Board of Secondary Education CBSE so that students can inculcate a practice of questioning things that may appear unusual to them. The concept of elements and compounds is an extremely important concept as elements form the periodic table without which chemistry is nothing and these concepts are further studied in higher classes for example they are again discussed in brief in unit one of the NCERT book of class 11 in the chapter called some basic concepts of chemistry. This chapter mainly talks about the basic concepts that have already been taught in earlier classes for example the concept of elements and compounds.

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The team has made the learning process much easier for students who may find it difficult to grasp the concept of ele
ments and compounds as the study notes provided by are written in an extremely simplified manner. As the main objective of producing these study notes is to help students get a clear knowledge of the basic foundations of chemistry so that they can excel in the exams and can easily study the complicated topics that will be taught later in the CBSE curriculum.

’s expert chemistry teachers have done extensive research and it is through their years of experience that they have accumulated these study notes that are based on the analysis of previous year question papers. Such research helps in producing quality notes for studious children who want to get a good score in the exam and want to have a strong base.

Key Concepts Needed to Understand Elements and Compounds

• What is A Mixture?

• Types of Mixtures

•  What is A Solution?

• Properties of A Solution

• Concentration of A Solution

• What is A Suspension?

• Properties of A Suspension

• What is A Colloidal Solution?

• Properties of A Colloid

• Separating the Components of A Mixture

• How Can We Separate A Mixture of Two Immiscible Liquids?

• How Can We Separate A Mixture of Salt And Ammonium Chloride?

• How Can We Separate A Mixture of Two Miscible Liquids?

• How Can We Obtain Different Gases From Air?

• How Can We Obtain Pure Copper Sulphate From An Impure Sample?

• Physical And Chemical Changes

• What Are The Types Of Pure Substances?

• Elements

• Compounds