In the first transition series,the metallic bond strength increases from ..... to .....

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$. Assertion $(A)$: In aqueous solutions $Cr^{2+}$ is reducing while $Mn^{3+}$ is oxidising in nature.
Reason $(R)$: Extra stability to half-filled electronic configuration is observed than incompletely filled electronic configuration.
In the light of the above statement,choose the most appropriate answer from the options given below:

Which of the following is the heaviest metal?

Platinum,palladium,iridium,etc.,are called noble metals because

What is the difference in atomic volume between $Au$ and $Cu$ in $22$ carat gold jewelry?

Why is the first ionisation enthalpy of $Cr$ lower than that of $Zn$?