Question

1 multiple choice 1 point the electron configuration for the neutral atom selenium is $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^4$. what is the electron configuration after 2 electrons are added (electron affinity)? $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6$ $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^3$ $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^2$ $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^4$ 2 multiple choice 1 point what is true about the following isoelectronic series? $n^{3-}, o^{2-}, f^-, ne, na^+, mg^{2+}$ $na^+, mg^{2+}$ have larger ionic radii than $n^{3-}, o^{2-},$ and $f^-$ all ions in the series have the same size ionic radii. $n^{3-}, o^{2-},$ and $f^-$ have larger ionic radii than $na^+, mg^{2+}$ 3 multiple choice 1 point

Explanation:

Question 1 (Electron Configuration After Adding 2 Electrons to Selenium)

Step 1: Recall Selenium's Electron Configuration

The neutral selenium atom has the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^4\).

Step 2: Determine the Effect of Adding 2 Electrons

When 2 electrons are added, they will fill the \(4p\) subshell (since \(4p\) has 4 electrons initially, and adding 2 will make it \(4p^6\)). So the new electron configuration is \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6\).

Step 1: Understand Isoelectronic Species

Isoelectronic species have the same number of electrons. For \(N^{3-}\), \(O^{2-}\), \(F^-\), \(Ne\), \(Na^+\), \(Mg^{2+}\), all have 10 electrons.

Step 2: Analyze Ionic Radii Trend

For isoelectronic species, as the nuclear charge (atomic number) increases, the ionic radius decreases. The nuclear charges are: \(N^{3-}\) (Z=7), \(O^{2-}\) (Z=8), \(F^-\) (Z=9), \(Ne\) (Z=10), \(Na^+\) (Z=11), \(Mg^{2+}\) (Z=12). So the ionic radii order is \(N^{3-}>O^{2-}>F^->Ne>Na^+>Mg^{2+}\). This means \(N^{3-}\), \(O^{2-}\), \(F^-\) have larger ionic radii than \(Na^+\) and \(Mg^{2+}\).

Answer:

The option with electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6\) (the first option among the choices for question 1).

Question 2 (Isoelectronic Series: \(N^{3-}, O^{2-}, F^-, Ne, Na^+, Mg^{2+}\))