Multiple Choice
In an atom, where are electrons most likely to be found?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which element has the ground state electron configuration [Ar] 4s^2 3d^{10} 4p^5?
A
Krypton (Kr)
B
Selenium (Se)
C
Gallium (Ga)
D
Bromine (Br)
Verified step by step guidance1
Identify the noble gas core in the given electron configuration. Here, [Ar] represents the electron configuration of Argon, which accounts for the first 18 electrons.
Count the electrons beyond the Argon core: 4s^2 means 2 electrons, 3d^{10} means 10 electrons, and 4p^5 means 5 electrons. Add these to the 18 electrons from Argon to find the total number of electrons.
Calculate the total number of electrons: 18 (from Argon) + 2 (4s) + 10 (3d) + 5 (4p) = 35 electrons.
Use the atomic number to identify the element. The atomic number corresponds to the total number of electrons in a neutral atom. Find the element with atomic number 35 on the periodic table.
Recognize that the element with atomic number 35 is Bromine (Br), which matches the given electron configuration.
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