ICSE Class 7 Chemistry, Unit 4: Atomic Structure

What this unit aims at

This theme will enable children to understand that every matter is made up of tiny particles known as atoms and molecules. Molecules are also made up of atoms. Hence atoms are the building blocks of matter. The physical and chemical properties of matter are governed by atoms. Therefore, the knowledge of the concepts of atoms of elements, molecules of elements and compounds and radicals of compounds is necessary to understand different processes and principles of Chemistry.

Your child should be able to

• define atom, molecule and radical
• discuss the significance of valency of elements and radicals
• define valency in terms of number of hydrogen atoms combined or replaced by one atom of the element
• apply the definition based on hydrogen atom to find out the valency of other elements and radicals
• correlate the valency of the elements with group number of periodic table

Key concepts in this unit

• Atoms, Molecules and Radicals
• An atom is the smallest particle of an element.
• It is not capable of independent existence.
• The properties of an element depend upon the atoms constituting it.
• A molecule is the smallest particle of an element or compound, capable of independent existence. It consists of one or more than one atom of the same or different elements.
• A radical is a single atom of an element or a group of atoms of different elements behaving as single charged unit.
• Atomicity (no. of atoms in an entity) of elements and compounds – mono atomic, di atomic, tri atomic, polyatomic.
• Associate the first 20 elements in the periodic table with their names and symbols
• Valency is the combining capacity of an element or the number of hydrogen atoms with which it combines or replaces.