Which is the electron configuration for boron?
A. $1 s^2 2 s^3$
B. $1 s^2 2 s^2 3 s^1$
C. $1 s^1 2 s^2 2 p^2$
D. $1 s^2 2 s^2 2 p^1$
Answer (2)
Boron has 5 electrons.
Fill the orbitals in order: 1s, 2s, 2p.
1 s 2 holds 2 electrons.
2 s 2 holds 2 electrons.
2 p 1 holds 1 electron.
The electron configuration is 1 s 2 2 s 2 2 p 1 .
Explanation
Determine the number of electrons Boron has an atomic number of 5, which means a neutral boron atom has 5 electrons. We need to fill the electron orbitals in the correct order according to the Aufbau principle.
Fill the 1s orbital The first orbital to fill is the 1s orbital, which can hold a maximum of 2 electrons. So we have 1 s 2 .
Fill the 2s orbital Next, we fill the 2s orbital, which can also hold a maximum of 2 electrons. So we have 1 s 2 2 s 2 .
Fill the 2p orbital We have filled 4 electrons so far (2 in 1s and 2 in 2s). We have 1 electron left to fill. The next orbital is the 2p orbital, which can hold up to 6 electrons. Since we only have 1 electron left, we put it in the 2p orbital. So we have 1 s 2 2 s 2 2 p 1 .
Final electron configuration Therefore, the electron configuration for boron is 1 s 2 2 s 2 2 p 1 .
Examples
Understanding electron configuration is crucial in chemistry for predicting how elements will interact to form chemical bonds. For example, knowing the electron configuration of boron helps us understand its bonding behavior in compounds like boron trifluoride ( B F 3 ), where boron forms three covalent bonds with fluorine atoms. The electron configuration also explains why boron can act as a Lewis acid, accepting an electron pair due to its incomplete octet.
The electron configuration for boron is 1 s 2 2 s 2 2 p 1 , indicating it has 2 electrons in the 1s orbital, 2 in the 2s orbital, and 1 in the 2p orbital. This configuration reflects the distribution of boron's 5 electrons according to the Aufbau principle. The correct multiple-choice answer is D: 1 s 2 2 s 2 2 p 1 .
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