Which orbital does possess the lowest energy in an atom?

Answer

To determine which orbital possesses the lowest energy in an atom, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Atomic Structure**:
- An atom consists of a nucleus at its center, surrounded by electrons that occupy various energy levels or shells.

2. **Identifying Energy Levels**:
- The energy levels are designated by the principal quantum number (n), which can take values like n = 1, 2, 3, etc. Each energy level can contain one or more sublevels (s, p, d, f).

3. **Sublevels and Orbitals**:
- Each energy level has sublevels:
- The **s** sublevel has 1 orbital (can hold 2 electrons).
- The **p** sublevel has 3 orbitals (can hold 6 electrons).
- The **d** sublevel has 5 orbitals (can hold 10 electrons).
- The **f** sublevel has 7 orbitals (can hold 14 electrons).

4. **Energy Order of Orbitals**:
- As we move away from the nucleus, the energy of the orbitals increases. The order of increasing energy for the orbitals is:
- 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7p

5. **Lowest Energy Orbital**:
- From the above order, it is clear that the **1s orbital** has the lowest energy of all the orbitals in an atom.

### Final Answer:
The orbital that possesses the lowest energy in an atom is the **1s orbital**.

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