Question

How to find valence electrons of cr

Answer 1

Chromium (Cr) has 6 valence electrons.

Answer 2

To find the valence electrons of Chromium (Cr):

1. Atomic Number: Chromium (Cr) has an atomic number of 24.
2. Electronic Configuration: The ground state electronic configuration of Chromium is an exception to the Aufbau principle due to the stability associated with a half-filled d-subshell.
   • Expected configuration: $[Ar] 3d^4 4s^2$
   • Actual configuration: $[Ar] 3d^5 4s^1$
3. Valence Electrons for Transition Metals: For transition metals (d-block elements), the valence electrons include the electrons in the outermost s-subshell (ns) and the electrons in the penultimate d-subshell ((n-1)d), because their energies are very close and they both participate in chemical bonding.
4. Count Valence Electrons: Based on the actual electronic configuration $[Ar] 3d^5 4s^1$:
   • Number of electrons in 4s = 1
   • Number of electrons in 3d = 5
   • Total valence electrons = $1 + 5 = 6$.

Therefore, Chromium has 6 valence electrons.

Explanation:

Chromium (Cr), atomic number 24, has an electronic configuration of $[Ar] 3d^5 4s^1$. For transition metals, valence electrons include both the outermost s-electrons and the (n-1)d electrons due to their similar energy levels and involvement in bonding. In Cr's case, these are the 1 electron in the 4s subshell and the 5 electrons in the 3d subshell, totaling 6 valence electrons.