Question

1. write the electron configuration, for mn and mn⁴⁺. how many electrons are in the valence energy level?

mn: ____
mn⁴⁺: ____
which neutral atom is isoelectronic with mn⁴⁺? ____
how many valence electrons does neutral mn have? ____

Explanation:

Step 1: Determine the atomic number of Mn

Manganese (Mn) has an atomic number of 25, so a neutral Mn atom has 25 electrons. The electron configuration of a neutral atom is built by filling orbitals in order of increasing energy (Aufbau principle). The electron configuration for Mn is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5$. We can also write it in a condensed form using the noble gas before Mn, which is Ar (argon, atomic number 18). So the condensed electron configuration is $[Ar] 4s^2 3d^5$.

Step 2: Determine the electron configuration of $\boldsymbol{Mn^{4+}}$

When Mn forms a $Mn^{4+}$ ion, it loses 4 electrons. Electrons are removed from the outermost shell first. The outermost shell for Mn is the 4th shell (with the 4s orbital). So we remove 2 electrons from the 4s orbital and 2 electrons from the 3d orbital (since we need to remove 4 total). So the electron configuration of $Mn^{4+}$ is $1s^2 2s^2 2p^6 3s^2 3p^6 3d^3$. In condensed form, using Ar, it is $[Ar] 3d^3$.

Step 3: Find the neutral atom isoelectronic with $\boldsymbol{Mn^{4+}}$

Isoelectronic species have the same number of electrons. $Mn^{4+}$ has $25 - 4 = 21$ electrons. The neutral atom with 21 electrons is scandium (Sc), since the atomic number of Sc is 21.

Step 4: Determine the number of valence electrons in neutral Mn

Valence electrons are the electrons in the outermost energy level. For Mn, the outermost energy level is the 4th level (n = 4). The electrons in the 4th level are in the 4s orbital (2 electrons) and the 3d orbital is in the n = 3 level (even though 3d is filled after 4s, the principal quantum number n = 3 for 3d). Wait, actually, the valence electrons for transition metals are often considered as the electrons in the outermost s orbital and the d orbital of the previous shell. But more accurately, for Mn, the electron configuration is $[Ar] 4s^2 3d^5$. The outermost energy level is n = 4 (the 4s electrons) and the 3d electrons are in n = 3, but in terms of valence electrons for transition metals, we consider both the 4s and 3d electrons? Wait, no, actually, the valence shell is the highest principal quantum number, which is n = 4 for Mn. The 4s orbital is in n = 4, and the 3d is in n = 3. But when Mn forms ions, it loses the 4s electrons first. However, the number of valence electrons for Mn: the electron configuration is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5$. The outermost energy level is n = 4, which has 2 electrons in 4s. But wait, transition metals can have valence electrons from both the s and d orbitals. Wait, actually, the valence electrons for Mn are 7? Wait, no, let's recall: the electron configuration of Mn is $[Ar] 4s^2 3d^5$. The valence electrons are the electrons in the highest principal quantum number (n = 4) and the d electrons of the (n - 1) shell? Wait, no, the definition of valence electrons is the electrons in the outermost shell (highest n) and the electrons in the d orbitals if they are in the (n - 1) shell but are involved in bonding. For Mn, the 4s electrons (n = 4) and 3d electrons (n = 3) are both considered valence electrons because Mn can use both in bonding. So the number of valence electrons is $2 + 5 = 7$? Wait, but when Mn forms $Mn^{4+}$, it loses 4 electrons: 2 from 4s and 2 from 3d. So the neutral Mn has 7 valence electrons? Wait, let's check the group number. Mn is in group 7 of the periodic table (transition metals, group 7B), so it has 7 valence electrons. So the number of valence electrons in neutral Mn is 7.

Answer:

s:

• Mn electron configuration: $[Ar] 4s^2 3d^5$ (or $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5$)
• $Mn^{4+}$ electron configuration: $[Ar] 3d^3$ (or $1s^2 2s^2 2p^6 3s^2 3p^6 3d^3$)
• Neutral atom isoelectronic with $Mn^{4+}$: Scandium (Sc)
• Number of valence electrons in neutral Mn: 7