This lecture explain the concept of valency electrons, stability of inert gases, concept of octet and duet rules, chemical bonds and the cause of their formation, how and why ions are formed. This lecture also explained the method of formation of ionic and covalent bonds, solubility, electrical conductivity and crystal formation with ionic and covalent bonds, the concept of metallic bonds, electric conductivity of metals with metallic bonds, identify the ionic and covalent compounds among the easily available local objects. Stay connected with our Facebook page and Facebook group 1. https://www.facebook.com/amaderschoolofficial/ (ফেসবুক পেইজ ) 2. https://www.facebook.com/groups/ovinob/ (ফেসবুক গ্রুপ)