Which of the following statement (s) is/are correct ?

Options

A. Electrons behaves as a wave
B. s-orbital is non-directional
C. An orbital can accommodate a maximum of two electron with parallel spins
D. The energies of the various sub-shell in the same shell are in the order `s gt p gt d gt f`

Explanation

To determine which of the statements provided in the question are correct, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: Electrons behave as a wave.**
- This statement is **correct**. Electrons exhibit dual nature, meaning they can behave both as particles and as waves. This concept is supported by de Broglie’s hypothesis, which suggests that every moving particle or object has an associated wave.

2. **Statement 2: S orbital is non-directional.**
- This statement is also **correct**. The S orbital is spherical in shape, which means it does not have a specific direction. Therefore, it is considered non-directional.

3. **Statement 3: An orbital can accommodate a maximum of two electrons with parallel spins.**
- This statement is **incorrect**. An orbital can hold a maximum of two electrons, but they must have opposite spins, not parallel spins. This is due to the Pauli exclusion principle, which states that no two electrons in an atom can have the same set of quantum numbers.

4. **Statement 4: The energies of the various subshells in the same shell are in the order s > p > d > f.**
- This statement is **incorrect**. The correct order of energy levels for subshells in the same shell is s < p < d < f. This is based on the n + l rule, where the subshell with the lower n + l value has lower energy.

### Summary of Correct Statements:
- **Correct Statements:** 1 and 2
- **Incorrect Statements:** 3 and 4

### Final Answer:
The correct statements are:
1. Electrons behave as a wave.
2. S orbital is non-directional.