Due to the poor shielding of 6s electrons, the shielding effect is insufficient to counter the decrease in radius caused by increasing nuclear charge, allowing Ta to have an identical radius to Nb.

Due to the excessive shielding of 4f electrons, the shielding effect is insufficient to counter the decrease in radius caused by increasing nuclear charge, allowing Ta to have an identical radius to Nb.

Due to the poor shielding of 4f electrons, the shielding effect is insufficient to counter the decrease in radius caused by increasing nuclear charge, allowing Ta to have an identical radius to Nb.

Due to the excessive shielding of 6s electrons, the shielding effect is insufficient to counter the decrease in radius caused by increasing nuclear charge, allowing Ta to have an identical radius to Nb.