Multiple Choice
Which of the following represents the correct electron configuration for a neutral atom of cobalt (atomic number 27)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct electron configuration for a neutral phosphorus (P) atom?
A
1s2 2s2 2p6 3s2 3p1
B
1s2 2s2 2p6 3s2 3p6
C
1s2 2s2 2p6 3s2 3p3
D
1s2 2s2 2p6 3s2 3p5
Verified step by step guidance1
Step 1: Identify the atomic number of phosphorus (P), which tells you the total number of electrons in a neutral atom. Phosphorus has an atomic number of 15, so it has 15 electrons.
Step 2: Recall the order in which electron orbitals are filled according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, and so on.
Step 3: Fill the orbitals with electrons following the order and the maximum number of electrons each orbital can hold: 1s (2 electrons), 2s (2 electrons), 2p (6 electrons), 3s (2 electrons), and 3p (6 electrons).
Step 4: Add the electrons stepwise until you reach the total of 15 electrons: 2 in 1s, 2 in 2s, 6 in 2p, 2 in 3s, and the remaining 3 electrons in 3p.
Step 5: Write the electron configuration by listing the orbitals and their electron counts: $1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^3$, which corresponds to the correct configuration for a neutral phosphorus atom.
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