As you can see, metallic radius is defined as one-half of the distance between the nuclei of two atoms in crystal or between two adjacent metal ions in the metallic lattice.
Metallic radii:
- decrease across the period due to increase in the effective nuclear charge.
- increase down the group due to increase in principal quantum number.
Points to Remember:
- The distance of each atom will be same because group of atoms are from the same metal.
- Metallic Radii decrease across the period because of increase in the effective nuclear charge.
- Metallic Radius increases down the group because new shell is added.
- Metallic radii are always biggest for the highest coordination number.
Group-wise Metallic Radii
Group 1: Alkali Metals
- Atomic Number 3: Li - 152 pm
- Atomic Number 11: Na - 186 pm
- Atomic Number 19: K - 227 pm
- Atomic Number 37: Rb - 248 pm
- Atomic Number 55: Cs - 262 pm
- Atomic Number 87: Fr - 270 pm (estimated)
Group 2: Alkaline Earth Metals
- Atomic Number 4: Be - 112 pm
- Atomic Number 12: Mg - 160 pm
- Atomic Number 20: Ca - 197 pm
- Atomic Number 38: Sr - 215 pm
- Atomic Number 56: Ba - 222 pm
- Atomic Number 88: Ra - 247 pm (estimated)
Group 3-12: Transition Metals
- Atomic Number 22: Ti - 147 pm
- Atomic Number 24: Cr - 140 pm
- Atomic Number 26: Fe - 126 pm
- Atomic Number 27: Co - 125 pm
- Atomic Number 28: Ni - 124 pm
- Atomic Number 29: Cu - 128 pm
- Atomic Number 30: Zn - 139 pm
- Atomic Number 40: Zr - 160 pm
- Atomic Number 42: Mo - 139 pm
- Atomic Number 74: W - 139 pm
- Atomic Number 78: Pt - 139 pm
Group 13: Boron Group
- Atomic Number 5: B (not metallic)
- Atomic Number 13: Al - 143 pm
- Atomic Number 31: Ga - 135 pm
- Atomic Number 49: In - 156 pm
- Atomic Number 81: Tl - 156 pm
Group 14: Carbon Group
- Atomic Number 6: C (not metallic in its common form)
- Atomic Number 14: Si (not metallic in its common form)
- Atomic Number 32: Ge - 122 pm (metalloid)
- Atomic Number 50: Sn - 140 pm
- Atomic Number 82: Pb - 175 pm
Group 15: Nitrogen Group
- Atomic Number 7: N (not metallic)
- Atomic Number 15: P (not metallic)
- Atomic Number 33: As - 120 pm (metalloid)
- Atomic Number 51: Sb - 140 pm
- Atomic Number 83: Bi - 156 pm
Group 16: Chalcogens
- Atomic Number 8: O (not metallic)
- Atomic Number 16: S (not metallic)
- Atomic Number 34: Se (not metallic)
- Atomic Number 52: Te - 140 pm (metalloid)
- Atomic Number 86: Po - 150 pm (metalloid)
Group 17: Halogens
- Atomic Number 9: F (not metallic)
- Atomic Number 17: Cl (not metallic)
- Atomic Number 35: Br (not metallic)
- Atomic Number 53: I (not metallic)
- Atomic Number 85: At (not metallic)
Summary
- Alkali and Alkaline Earth Metals have larger metallic radii due to their larger atomic sizes and single/double valence electrons.
- Transition Metals exhibit varying metallic radii due to their unique electron configurations and bonding characteristics.
- Metalloids (like Ge, As, and Sb) have intermediate metallic properties.
- Nonmetals (like N, O, F) and many elements in Groups 14 to 17 do not have metallic radii as they do not participate in metallic bonding.
| Atomic Number | Element | Metallic Radius (pm) |
|---|