Question

1. In terms of potential energy, state why atoms tend to bond in nature.

1. Which member of each of the following pair would you expect to have the highest melting point? Explain your reasoning.

a. CaO or RbI

b. LiF or NaCl

c. CH4 or CH3Cl

Answer 1

Atoms tend to bond in nature as they want to attain stability. Some atoms have their octet incomplete so to complete octet,they bond with each other.Potential energy is inversely proportional to stability, i.e when potential energy of atoms is more ,then they are unstable so potential energy should be minimum for maximum stability.

CaO has higher melting point than RbI as calcium has comparable size to oxygen ,thus have strong bonding interactions as compared to RbI where Rb carry single +ve charge and therefore its charge by size ratio is large as compared to Calcium. So calcium will make stronger bonding interaction ,thus high melting point.

In LiF ,both Li+ and F- have high charge and small size . Whereas Na + and Cl- have same charge but small size so interactions in LiF will be higher than in NaCl so LiF has higher melting point than NaCl.

CH4 is a non polar covalent compound while CH3CL is a polar compound with strong interaction between carbon and chlorine. Also Ch4 Is a gas , we can't find its meting point so ch3cl has high melting point between these two compounds.