The magnetic quantum number of an atom`s electron refers to the `orientation` of the orbital within a specific energy level. So, option 1 is correct.

To break down the other options:

Option 2, `shape,` is more closely related to the azimuthal (or angular momentum) quantum number, which determines the shape of the orbital.

Option 3, `size`, refers to the principal quantum number which determines the size and energy level of the atomic orbital, not the magnetic quantum number.

Option 4, `spin`, refers to the spin quantum number, which describes the spin (clockwise or anticlockwise) of the electron within the atomic orbital.

In summary, each quantum number describes a different property of the electron in an atom, and in this case, the magnetic quantum number is correctly associated with the `orientation` of the orbital.