Let's find the correct electron configuration for the element with atomic number 20.
The atomic number of 20 corresponds to the element Calcium (Ca). The distribution of electrons in an atom follows specific rules known as the Aufbau principle, which states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.
The order in which the atomic orbitals fill can be remembered using the following sequence:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p...
Starting with the lowest energy level, we can distribute the 20 electrons of Calcium:
1. The 1s orbital can hold 2 electrons: [tex]\(1s^2\)[/tex]
2. The 2s orbital can hold 2 electrons: [tex]\(2s^2\)[/tex]
3. The 2p orbital can hold 6 electrons: [tex]\(2p^6\)[/tex]
4. The 3s orbital can hold 2 electrons: [tex]\(3s^2\)[/tex]
5. The 3p orbital can hold 6 electrons: [tex]\(3p^6\)[/tex]
6. The 4s orbital can hold 2 electrons: [tex]\(4s^2\)[/tex]
Summing these, we have:
- [tex]\(1s^2\)[/tex] = 2 electrons
- [tex]\(2s^2\)[/tex] = 2 electrons
- [tex]\(2p^6\)[/tex] = 6 electrons
- [tex]\(3s^2\)[/tex] = 2 electrons
- [tex]\(3p^6\)[/tex] = 6 electrons
- [tex]\(4s^2\)[/tex] = 2 electrons
Adding these together gives us [tex]\(2 + 2 + 6 + 2 + 6 + 2 = 20\)[/tex] electrons.
Therefore, the correct electron configuration for calcium (with atomic number 20) is:
[tex]\[1s^2 2s^2 2p^6 3s^2 3p^6 4s^2\][/tex]
Thus, the correct answer is:
[tex]\[B. \ 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 \][/tex]
