Which element, as a 2+ cation, has the electron configuration1s22s22p63s23p63d9?A) CaB) CuC) ZnD) CoE) Pd

To determine which element, as a 2+ cation, has the electron configuration $1s^2 2s^2 2p^6 3s^2 3p^6 3d^9$, follow these steps:

1. Identify the given electron configuration: $1s^2 2s^2 2p^6 3s^2 3p^6 3d^9$.

2. Count the total number of electrons in the configuration:

   • $1s^2$ has 2 electrons.
   • $2s^2$ has 2 electrons.
   • $2p^6$ has 6 electrons.
   • $3s^2$ has 2 electrons.
   • $3p^6$ has 6 electrons.
   • $3d^9$ has 9 electrons.
   • Total: $2 + 2 + 6 + 2 + 6 + 9 = 27$ electrons.

3. Determine the atomic number of the neutral atom: Since the element is in the form of a 2+ cation, it has lost 2 electrons. Therefore, the neutral atom must have $27 + 2 = 29$ electrons.

4. Identify the element with atomic number 29: The periodic table shows that the element with atomic number 29 is Copper (Cu).

5. Verify the electron configuration of the neutral atom: The electron configuration of neutral Copper (Cu) is $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1$. When it loses 2 electrons to form a 2+ cation, the configuration becomes $1s^2 2s^2 2p^6 3s^2 3p^6 3d^9$.

Therefore, the correct answer is:

B) Cu