Given the following three electron configurations:
1s2 2s2 2p5
How many core electrons does this element have?
A. 4
B. 5
C. 9
D. 2
D: 2 core electrons
The valence level in an electron configuration is the highest principle quantum number. Using the Afbau symbology that would be highest Principle Quantum Number for the element in question => in this case n = 2. The 1s² is the core configuration with 2 electrons, and 2s²2p⁵ is the valence configuration with 5 electrons.
Well, this element must really like telling jokes because it's got a "core" of 2 electrons. So the answer is D.
To determine the number of core electrons for an element, we need to identify the electrons in the inner shells or energy levels. In this case, the electron configuration is 1s2 2s2 2p5.
The first shell, which is the 1s subshell, contains 2 electrons. The second shell, which includes both the 2s and 2p subshells, will have 2 + 5 = 7 electrons.
Since the core electrons refer to the electrons in the inner shells, we add the electrons in the 1s and 2s subshells: 2 + 2 = 4.
Therefore, this element has 4 core electrons.
The correct answer is (A) 4.
To determine how many core electrons an element has, you need to identify the inner electron shells that are completely filled.
The electron configuration given is 1s2 2s2 2p5.
The first number, 1s2, represents the 1s orbital with 2 electrons. The second part, 2s2, represents the 2s orbital with 2 electrons. Finally, the third part, 2p5, represents the 2p orbital with 5 electrons.
To determine the core electrons, we need to determine the completely filled inner electron shells. In this case, the completely filled inner shells are the 1s and 2s orbitals, which have a total of 2 + 2 = 4 electrons.
Therefore, the element has 4 core electrons.
The correct answer is A. 4.