Metal

V³⁺

Cr³⁺

Mn³⁺

Fe³⁺

Co³⁺

E_g(eV)

2.62

3.33

1.69

4.02

3.82

Electron affinity A (eV)

−6.97

−7.53

−5.80

−8.02

−7.88

Electronegativity χ (eV)

5.66

5.87

4.95

6.01

5.97

Chemical hardness (eV)

1.31

1.66

0.85

2.01

1.91

Chemical softness S (eV)

0.38

0.30

0.59

0.25

0.26