In the ground state, an element has `13` electrons in its `M` shell. The element is

Options

A. cobalt
B. chromium
C. nickel
D. iron

Explanation

To determine the element with 13 electrons in its M shell, we need to analyze the electron configuration step by step.

### Step 1: Understand Electron Shells
The electron shells are labeled as K, L, M, etc. Each shell can hold a certain number of electrons:
- K shell can hold a maximum of 2 electrons.
- L shell can hold a maximum of 8 electrons.
- M shell can hold a maximum of 18 electrons.

### Step 2: Determine the Total Number of Electrons
Since the element has 13 electrons in its M shell, we need to find out how many total electrons there are in the atom. The M shell can hold up to 18 electrons, but we need to consider the electrons in the K and L shells as well.

### Step 3: Fill the K and L Shells
- The K shell can hold 2 electrons, so we fill it first:
- K shell: 2 electrons
- The L shell can hold 8 electrons, so we fill it next:
- L shell: 8 electrons

Now, we have filled:
- K shell: 2 electrons
- L shell: 8 electrons
- M shell: 13 electrons (as given in the question)

### Step 4: Calculate the Total Number of Electrons
Now we can calculate the total number of electrons:
- Total electrons = Electrons in K shell + Electrons in L shell + Electrons in M shell
- Total electrons = 2 + 8 + 13 = 23 electrons

### Step 5: Identify the Element
The total number of electrons corresponds to the atomic number of the element. An atomic number of 23 corresponds to the element Vanadium (V).

### Conclusion
The element with 13 electrons in its M shell is Vanadium (V).

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