Which of the following elements has the electronic configuration [Kr] 5s2 4d10 5p5?
Correct Answer: Astatine (At)
- Step 1: Understand that the electronic configuration [Kr] 5s2 4d10 5p5 represents the arrangement of electrons in an atom.
- Step 2: Recognize that [Kr] stands for the electron configuration of Krypton, which has 36 electrons.
- Step 3: Add the electrons from the configuration: 2 electrons in 5s, 10 electrons in 4d, and 5 electrons in 5p.
- Step 4: Calculate the total number of electrons: 36 (from Kr) + 2 + 10 + 5 = 53.
- Step 5: The atomic number of an element corresponds to the number of electrons in a neutral atom, so the atomic number is 85.
- Step 6: Look up the element with atomic number 85 in the periodic table, which is Astatine (At).
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