The shorthand electron configuration of a sodium ion Na+ is [Ne].
The Correct Answer and Explanation is:
The correct shorthand electron configuration of a sodium ion Na+ is A. [Ne].
Explanation:
To determine the shorthand electron configuration for the sodium ion (Na+), we must first understand the electron configuration of a neutral sodium atom (Na) and then consider how the formation of an ion affects it.
1. Neutral Sodium Atom (Na):
First, we locate sodium (Na) on the periodic table. It is in Group 1 and Period 3, and its atomic number is 11. This atomic number indicates that a neutral sodium atom has 11 protons in its nucleus and, to maintain electrical neutrality, 11 electrons orbiting the nucleus.
We can write the full electron configuration for these 11 electrons by filling the atomic orbitals in order of increasing energy, following the Aufbau principle:
1s², 2s², 2p⁶, 3s¹
(2 + 2 + 6 + 1 = 11 electrons)
The shorthand, or noble gas, configuration for a neutral sodium atom would use the noble gas from the previous period (Period 2), which is Neon (Ne). Neon’s configuration is 1s²2s²2p⁶. So, the shorthand for a neutral sodium atom is [Ne] 3s¹.
2. Sodium Ion (Na+):
The question asks for the configuration of a sodium ion, Na+. The positive one (+) charge signifies that the neutral sodium atom has lost one electron. Atoms tend to lose or gain electrons to achieve the stable electron configuration of a noble gas, a state often referred to as a full octet in the valence shell.
For sodium, the outermost electron is the single electron in the 3s orbital (the valence electron). By losing this one electron, sodium achieves a more stable state.
So, we start with the neutral Na atom’s 11 electrons and subtract one:
11 electrons – 1 electron = 10 electrons.
The full electron configuration for the resulting Na+ ion, which now has 10 electrons, is:
1s²2s²2p⁶
3. Shorthand Configuration for Na+:
The question specifically asks for the shorthand configuration. We look for the noble gas that has the same electron configuration as the Na+ ion. The noble gas with 10 electrons is Neon (Ne), which has the exact configuration 1s²2s²2p⁶. Therefore, the shorthand electron configuration for the sodium ion (Na+) is simply [Ne].
Analysis of Other Options:
- B. [Ar]: Represents Argon, which has 18 electrons. This is incorrect.
- C. [He]: Represents Helium, which has 2 electrons. This is incorrect.
- D. 1s²2s²2p⁶: This is the correct full electron configuration for Na+, but the question asks for the shorthand notation.
- E. 1s²1p⁶2s²: This notation is fundamentally incorrect as the 1p orbital does not exist in quantum mechanics.
