A sodium atom attains a stable configuration by losing one electron from its outermost shell.
Sodium (Na), an alkali metal found in the first column of the periodic table, naturally exists with an electron configuration that isn't the most stable possible. Atoms tend to seek configurations that resemble those of the noble gases, which have full valence electron shells and are very unreactive.
Understanding Sodium's Unstable Configuration
As per the reference provided, a sodium atom's electron configuration is 1s²2s²2p⁶3s¹.
Let's break this down:
- 1s²: The first energy level (n=1) has 2 electrons in the 's' subshell. This shell is full.
- 2s²2p⁶: The second energy level (n=2) has 2 electrons in the 's' subshell and 6 electrons in the 'p' subshell. This shell contains a total of 2 + 6 = 8 electrons and is also full.
- 3s¹: The third energy level (n=3) has only 1 electron in the 's' subshell. This is the outermost, or valence, shell.
This configuration, with just one electron in the outermost shell, makes the sodium atom reactive. It's much easier for the atom to get rid of this single outer electron than to gain seven more to fill the third shell (which requires 8 electrons for a full 's' and 'p' subshell).
Achieving Stability by Losing an Electron
To achieve a stable configuration, a sodium atom undergoes ionization. It loses one electron as Na⁺−1s²2s²2p⁶.
Here's what happens:
- The single electron in the 3s orbital is removed.
- The atom is left with 11 protons (its atomic number remains the same) but now only 10 electrons (11 - 1 = 10).
- This imbalance results in a net positive charge, forming a sodium ion, Na⁺.
The electron configuration of the resulting sodium ion (Na⁺) is 1s²2s²2p⁶.
| Species | Protons | Electrons | Charge | Electron Configuration | Stability |
|---|---|---|---|---|---|
| Sodium Atom (Na) | 11 | 11 | 0 | 1s²2s²2p⁶3s¹ | Unstable |
| Sodium Ion (Na⁺) | 11 | 10 | +1 | 1s²2s²2p⁶ | Stable (like Neon) |
Why is 1s²2s²2p⁶ Stable?
The configuration 1s²2s²2p⁶ is the same as that of the noble gas Neon (Ne). This configuration means the outermost occupied electron shell (the second energy level, n=2) is completely filled with 8 electrons (2 in 2s and 6 in 2p). A full outer shell, known as a stable octet (or duplet for the first shell), represents a state of lower energy and higher stability for the atom or ion.
Therefore, by losing that single valence electron, the sodium atom transforms into a positively charged ion (Na⁺) with a stable, noble gas-like electron configuration. This process is fundamental to how sodium forms chemical bonds, particularly ionic bonds with elements that readily gain electrons, such as chlorine (forming NaCl, table salt).
