How many electrons are there in the 2p orbitals of selenium?
The correct answer and explanation is:
Correct Answer: 6 electrons
Explanation:
To determine the number of electrons in the 2p orbitals of selenium, it is important to first understand the electron configuration of the element.
Selenium (Se) has an atomic number of 34, which means a neutral selenium atom has 34 electrons.
Electrons in an atom occupy energy levels (or shells), and within each energy level are sublevels (s, p, d, f). These are filled in a specific order based on their energy, known as the Aufbau principle. The typical order of filling is:
1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → etc.
So, to write the electron configuration of selenium:
1s²
2s²
2p⁶
3s²
3p⁶
4s²
3d¹⁰
4p⁴
Adding the superscripts gives 2 + 2 + 6 + 2 + 6 + 2 + 10 + 4 = 34 electrons.
Now, focus on the 2p orbital. According to the configuration, 2p⁶ shows that there are 6 electrons in the 2p orbitals of selenium.
The 2p sublevel contains three orbitals: 2px, 2py, and 2pz. Each of these can hold a maximum of 2 electrons, so the 2p sublevel can hold up to 6 electrons total. In selenium, this sublevel is completely filled.
This number does not change regardless of the total electrons in the atom. Electrons always fill the lower energy levels first. Therefore, even though selenium has 34 electrons, only 6 of those reside in the 2p sublevel, and they are the same for all elements with atomic number 10 or higher.
In conclusion, the 2p orbitals in selenium hold 6 electrons.