Constituents of matter

Key Concepts

1. Atoms
2. Molecules
3. Compounds
4. Elements
5. Structure of some substances

Introduction: 

Constituents of matter an atom is the smallest unit of matter that retains all the properties of an element. Atoms combine to form molecules. For example, water is composed of hydrogen and oxygen atoms that have combined to form water molecules. Now in this chapter, we are going to learn the constituents of matter and the structures of some compounds. 

Constituents of Matter:  

Matter has mass and occupies space. Matter is defined as everything composed of elementary fermions. 

Matter is classified into mixtures and pure substances 

Atom: 

An atom consists of the nucleus at the center. The electrons are surrounded to the nucleus, in which electrons are negatively charged, and nucleus is the combination of protons and neutrons. The protons are positively charged particles. 

Electron, proton and neutrons are the sub-atomic particles of an atom 

Atom is the basic constituent unit of matter, which does not exist independently and forms ions and molecules. 

Elements: 

An element is a pure substance formed with atoms that contains the same number of protons. 

Element is the basic form of matter which cannot be broken down into simpler particles. 

Some of the elements which are there in the periodic table are in their elementary form. 

Examples: Hydrogen (H₂) 

                    Oxygen (O₂) 

                    Fluorine(F₂) 

Here is the differentiation of atom and element: 

Molecule:  

When two or more atoms combine to form a molecule as in which molecule is an independently existing 

Molecules are classified into the following: 

Monoatomic molecules: Helium (He), Neon (Ne) 

Diatomic molecule: Hydrogen (H₂), Oxygen (O₂), Fluorine(F₂). 

Triatomic molecule: Ozone(O₃). 

Polyatomic molecule: Phosphorous(P₄), Sulphur (S₈) 

Compound:  

A compound is a substance composed of the same or identical molecules composed of two or more elements. 

A molecule consisting of atoms of only one element is, therefore, not a compound. 

Summary: 

• An atom consists of the nucleus at the center. The electrons are surrounded to the nucleus, in which electrons are negatively charged, and nucleus is the combination of protons and neutrons. 

• A compound is a substance composed of the same or identical molecules composed of two or more elements. 
• An element is a pure substance formed with atoms that contains the same number of protons. 
• Element is the basic form of matter which cannot be broken down into simpler particles.