To find the number of electrons having l m value equal to zero in 26Fe, we need to understand the electronic configuration of iron (Fe).

Electronic configuration of Iron (Fe)

Iron (Fe) has an atomic number of 26, which means it has 26 electrons. The electronic configuration of Fe is:

1s2 2s2 2p6 3s2 3p6 4s2 3d6

Here, the last orbital, i.e., the 3d orbital, has six electrons.

Number of electrons having l m value equal to zero in 26Fe

The value of l determines the shape of the orbital, and the value of m determines the orientation of the orbital in space. For l=0, there is only one possible value of m, which is also zero. This means that an electron in an l=0 orbital has no preferred direction in space.

In the electronic configuration of Fe, the 4s and 3d orbitals are partially filled. Since the value of l for the 4s orbital is zero, there are 2 electrons in the 4s orbital with l=0 and m=0.

For the 3d orbital, there are 5 different orbitals: dxy, dyz, dxz, dx2-y2, and dz2. Each orbital can hold a maximum of 2 electrons, and since there are 6 electrons in the 3d orbital, one of the orbitals must have 2 electrons, and the other 4 orbitals must have 1 electron each.

Now, for the dxy, dyz, and dxz orbitals, the value of l is 2, which means there are no electrons with l=0 in these orbitals.

For the dx2-y2 and dz2 orbitals, the value of l is 2 and the value of m can be either +2, +1, 0, -1, or -2. This means that there are two electrons in the 3d orbital with l=0 and m=0, since the dx2-y2 and dz2 orbitals have this value.

Therefore, the total number of electrons in Fe with l=0 is 2+2=4.

However, the question specifically asks for the number of electrons with l m value equal to zero. This means that only the 4s electrons count, since they have l=0 and m=0. Therefore, the number of electrons in Fe with l m value equal to zero is 2.

Hence, the correct answer is option 'A' (13).