Which of the following metals does not show variable valency?

Four successive members of the first series of the transition metals are listed below. For which one of them is the standard electrode potential $(E^o_{M^{2+}/M})$ value positive?

Due to covalent bonding,the transition metals are

Which of the following statements is not true in regard to transition elements?

For the first row transition metals,the $E^{\Theta }$ values are:

$E^{\Theta }$	$V$	$Cr$	$Mn$	$Fe$	$Co$	$Ni$	$Cu$
$(M^{2+}/M)$	$-1.18$	$-0.91$	$-1.18$	$-0.44$	$-0.28$	$-0.25$	$+0.35$

Explain the irregularity in the above values.

The order of melting points of $Cr$,$Mo$,and $W$ is: