The total energy of an electron in an atom in an orbit is `-3.4eV`. Its kinetic and potential energies are, respectively:

Options

A. 3.4eV,3.4eV
B. `-3.4eV,-3.4ev`
C. `-3.4eV,-6.8eV`
D. `3.4 eV,-6.8eV`

Explanation

To solve the problem, we need to find the kinetic energy (K.E.) and potential energy (P.E.) of an electron in an atom, given that the total energy (E) is -3.4 eV.

### Step-by-Step Solution:

1. **Understanding Total Energy**:
The total energy (E) of an electron in an orbit is given by the sum of its kinetic energy (K.E.) and potential energy (P.E.). Mathematically, this can be expressed as:
\[ E = K.E. + P.E. \]

2. **Relation Between K.E. and P.E.**:
In a hydrogen-like atom, the potential energy (P.E.) is related to the kinetic energy (K.E.) by the equation:
\[ P.E. = -2 \times K.E. \]
This means that the potential energy is always negative and is twice the magnitude of the kinetic energy.

3. **Substituting Total Energy**:
We can substitute the expression for potential energy into the total energy equation:
\[ E = K.E. + (-2 \times K.E.) \]
Simplifying this gives:
\[ E = K.E. - 2 \times K.E. = -K.E. \]
Therefore, we can express kinetic energy in terms of total energy:
\[ K.E. = -E \]

4. **Calculating K.E.**:
Given that the total energy \( E = -3.4 \, \text{eV} \):
\[ K.E. = -(-3.4 \, \text{eV}) = 3.4 \, \text{eV} \]

5. **Calculating P.E.**:
Now, using the relationship between potential energy and kinetic energy:
\[ P.E. = -2 \times K.E. = -2 \times 3.4 \, \text{eV} = -6.8 \, \text{eV} \]

### Final Answer:
- Kinetic Energy (K.E.) = \( 3.4 \, \text{eV} \)
- Potential Energy (P.E.) = \( -6.8 \, \text{eV} \)