Let's analyze the given electron configuration step by step to identify the type of element it represents.
1. The provided electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 3d^7 4s^2.
2. Breaking down the configuration:
- 1s^2: 2 electrons in the 1s subshell
- 2s^2: 2 electrons in the 2s subshell
- 2p^6: 6 electrons in the 2p subshell
- 3s^2: 2 electrons in the 3s subshell
- 3p^6: 6 electrons in the 3p subshell
- 3d^7: 7 electrons in the 3d subshell
- 4s^2: 2 electrons in the 4s subshell
3. Summing these up, we get the total electrons as:
2 (from 1s^2) + 2 (from 2s^2) + 6 (from 2p^6) + 2 (from 3s^2) + 6 (from 3p^6) + 7 (from 3d^7) + 2 (from 4s^2) = 27 electrons.
4. Having 27 electrons means the atom is cobalt (Co) because cobalt has an atomic number of 27.
5. Next, consider the position of cobalt on the periodic table. Cobalt is located in the d-block, which contains transition elements. The term "transition element" refers to elements that have partially filled d orbitals.
6. The given electron configuration ends with 3d^7 4s^2, confirming that it has a partially filled d orbital.
As a result, the element with this electron configuration is a transition element.
Therefore, the answer is:
C. transition element.
