In actinides, electrons are progressively filled in the 5f orbitals. They exhibit several oxidation states, the preferred oxidation state being +4. Some of them like U, Np, Pu etc. can exist in +6 oxidation state also. 
Actinides are heavy metals having high melting points and forming alloys with other metals. Thorium, uranium and plutonium are used as nuclear fuels.
| Element (Symbol) | Atomic Number | Electronic Configuration |
| Actinium (Ac) | 89 | 6d17s2 |
| Thorium(Th) | 90 | 6d27s2 |
| Protoactinum(Pa) | 91 | 5f26d17s2 |
| Uranium(U) | 92 | 5f36d17s2 |
| Neptunium (Np) | 93 | 5f46d17s2 |
| Plutonium (Pu) | 94 | 5f67s2 |
| Americium(Am) | 95 | 5f77s2 |
| Curium(Cm) | 96 | 5f76d17s2 |
| Berkelium(Bk) | 97 | 5f86d17s2 |
| Californium(Cf) | 98 | 5f107s2 |
| Eisteinium(Es) | 99 | 5f117s2 |
| Fermium(Fm) | 100 | 5f127s2 |
| Mendelevium(Md) | 101 | 5f137s2 |
| Nobelium(No) | 102 | 5f147s2 |
| Lawrencium(Lr) | 103 | 5f145d17s2 |
Actinides are heavy metals having high melting points and forming alloys with other metals. Thorium, uranium and plutonium are used as nuclear fuels.