Why do some chemical bonds need more energy to break?

Chemical bonds have different strengths. Atoms that are more strongly attracted to each other have a stronger bond strength and are more stable. More energy is required to break stronger chemical bonds as compared to the energy required to break weaker chemical bonds. 

There are two main types of chemical bonds – ionic bonds and covalent bonds. Ionic bonds are formed by the mutual attraction between oppositely charged ions. Covalent bonds are formed by the sharing of electrons between nuclei. Ionic bonds are generally stronger than covalent bonds because of the coulombic attraction between ions of opposite charges. Hence ionic chemical bonds will need more energy to break.