Elements and Compounds | Chemistry for EmSAT Achieve PDF Download

Element Definition

• Elements – Elements constitute the simplest chemical substances in which all the atoms are exactly the same.

Compound Definition

• Compounds – Compounds are chemical substances made up of two or more elements that are chemically bound together in a fixed ratio.

Chemistry is the study of the structures, physical properties, and chemical properties of material substances. It is very important to understand that all gases, liquids, and solids are not the same. All are different in terms of their composition. This is the reason why the classification of the matter is very important.

Classification of Matter

• Elements
• Compounds
• Mixtures

What is a Compound?

A compound refers to the product obtained when two or more elements chemically combine in a fixed ratio by mass. It can be described as a substance composed of two or more different types of elements in a specific ratio of their atoms. During the combination of elements, certain individual properties are lost, and the resulting compound exhibits new properties.

Chemical Formula: Compounds are represented using chemical formulas, which symbolically represent the proportions of atoms constituting a particular compound. For example, water is represented by the chemical formula H₂O, indicating that two hydrogen atoms and one oxygen atom have combined to form one molecule of H₂O. Common salt is represented by the chemical formula NaCl, indicating the combination of one sodium atom and one chlorine atom to form one molecule of NaCl.

Types of Compounds

Compounds can be classified into two types: molecular compounds and salts. In molecular compounds, atoms are bonded together through covalent bonds, whereas salts are held together by ionic bonds. These two types of bonds are the building blocks of every compound.

Examples of Compounds

• Examples of compounds include water (H₂O), hydrogen peroxide (H₂O₂), etc. In water, the chemical formula indicates the combination of 2 hydrogen atoms with 1 oxygen atom. Similarly, hydrogen peroxide consists of 2 hydrogen atoms and 2 oxygen atoms.
• An example of a salt compound is table salt (NaCl), which consists of 1 sodium atom and 1 chlorine atom.

Examples of some commonly used compounds and their molecular formula: