Hydrogen bonds are formed in many compounds e.g., H₂O, HF, NH₃ . The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is :

(i) HF > H₂O > NH₃

(ii) H₂O > HF > NH₃

(iii) NH₃ > HF > H₂O

(iv) NH₃ > H₂O > HF

He₂ has zero bond order hence it does not exist.

The three fundamental laws of chemistry are - Law of Definite Proportions, Law of Conservation of Mass, and Law of Multiple Proportions.

The three types of chemical bonds are - ionic, metallic and covalent bonds. When the electrons transfer between the atoms, they form the Ionic bonds by producing charged ions that are attracted to each other. When atoms share electrons, covalent bonds are created. When metal atoms share a sea of del