Which is the electron configuration for nobelium (No)?
A. [ Rn ] 7 s^2 5 f^{14}
B. [ Rn ] 7 s^2 5 f^7
C. [ Ne ] 3 s^2 3 p^7
D. [ Xe ] 6 s^2 5 d^1
Answer (1)
Determine the number of electrons to configure: Nobelium (No) has 102 electrons.
Identify the preceding noble gas: Radon (Rn) has 86 electrons, leaving 16 electrons to configure.
Fill the orbitals according to the Aufbau principle: 7 s 2 (2 electrons) and 5 f 14 (14 electrons).
The electron configuration for Nobelium (No) is [ R n ] 7 s 2 5 f 14 .
Explanation
Understanding the Problem We need to determine the electron configuration of Nobelium (No), which has an atomic number of 102. This means a neutral Nobelium atom has 102 electrons. We will use the Aufbau principle to determine the electron configuration.
Accounting for Electrons Nobelium is in the f-block of the periodic table. Its electron configuration will include the electron configuration of the noble gas that precedes it, which is Radon (Rn), with an atomic number of 86. Therefore, we need to account for the remaining 102 - 86 = 16 electrons.
Filling the 7s Orbital The general form of the electron configuration will be [ R n ] + additional electrons . After Radon, we fill the 7 s orbital, which can hold 2 electrons. So we have 7 s 2 . This accounts for 2 of the 16 electrons, leaving 16 - 2 = 14 electrons to be placed.
Filling the 5f Orbital Next, we fill the 5 f orbital, which can hold up to 14 electrons. Since we have exactly 14 electrons remaining, we fill the 5 f orbital completely, resulting in 5 f 14 .
Final Answer Therefore, the electron configuration of Nobelium is [ R n ] 7 s 2 5 f 14 . Comparing this to the given options, we find that the correct answer is [ R n ] 7 s 2 5 f 14 .
Examples
Understanding electron configurations helps predict the chemical properties of elements. For example, knowing the electron configuration of Nobelium allows us to understand how it might interact with other elements to form chemical bonds. This knowledge is crucial in fields like materials science, where the properties of new materials are designed based on the electronic structure of their constituent elements.
