Use the periodic table to write the electron configuration of selenium (Se). Place the sublevels in order of filling from least energy to most energy.
Answer (1)
Determine the number of electrons in Selenium (Se), which is 34.
Apply the Aufbau principle to determine the filling order of orbitals.
Fill each subshell with the appropriate number of electrons according to the Aufbau principle.
The electron configuration for Selenium (Se) is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 4 .
Explanation
Understanding the Problem We want to determine the electron configuration of Selenium (Se), placing the sublevels in order of filling from least energy to most energy. Selenium has an atomic number of 34, meaning a neutral Se atom has 34 electrons. We will use the Aufbau principle to fill the orbitals in order of increasing energy.
Applying the Aufbau Principle The Aufbau principle dictates the filling order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, etc. We fill each subshell with the appropriate number of electrons. Remember that s orbitals can hold up to 2 electrons, p orbitals can hold up to 6 electrons, and d orbitals can hold up to 10 electrons.
Filling the Orbitals
Start with the 1s orbital: 1 s 2 (2 electrons)
Move to the 2s orbital: 1 s 2 2 s 2 (4 electrons)
Fill the 2p orbital: 1 s 2 2 s 2 2 p 6 (10 electrons)
Fill the 3s orbital: 1 s 2 2 s 2 2 p 6 3 s 2 (12 electrons)
Fill the 3p orbital: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 (18 electrons)
Fill the 4s orbital: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 (20 electrons)
Fill the 3d orbital: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 (30 electrons)
Finally, fill the 4p orbital until we reach 34 electrons total: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 4 (34 electrons)
Final Electron Configuration The electron configuration of Selenium (Se) is therefore: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 4 .
Examples
Understanding electron configurations helps predict how elements will interact to form chemical bonds. For example, knowing Selenium's electron configuration allows us to understand its bonding behavior with other elements, which is crucial in designing new materials or understanding chemical reactions. This knowledge is fundamental in fields like materials science, chemistry, and electronics, where the properties of substances are directly related to their electronic structure.
