The Nitrogen Family – From Air to Metal
Think about the air you breathe. Nearly 78% of it is nitrogen gas — colourless, odourless, and so unreactive that it just sits there. Now imagine a grey, shiny solid that glows in the dark. That's phosphorus. And then there's arsenic, once used as a poison; antimony, used in fireproofing; and bismuth, a heavy metal with a rainbow oxide layer.
These five elements — nitrogen, phosphorus, arsenic, antimony, bismuth — make up Group 15 of the periodic table. They start as a gas, become a non-metal, then a metalloid, and finally a metal. That's the single most important pattern: metallic character increases as you go down the group.
The Common Thread: Five Valence Electrons
Every element in Group 15 has the electron configuration ns2np3 in its outermost shell. Five valence electrons means they need three more to complete an octet — hence the common oxidation state of −3 (as in NHX3, ammonia, or PHX3, phosphine).
But because the ns2 pair can also be lost or shared, you get +3 (e.g., NClX3, PClX3) and +5 (e.g., HNOX3, PClX5). The +5 state becomes less stable as you go down — bismuth hardly ever shows +5 because its 6s electrons are too tightly held (the inert pair effect).
General outer configuration: ns2np3
Common oxidation states: −3, +3, +5
The Downward Trend: From Gas to Metal
| Property | N | P | As | Sb | Bi |
|---|
| Nature | Non-metal | Non-metal | Metalloid | Metalloid | Metal |
| State at room temp | Gas | Solid (white/red) | Solid | Solid | Solid |
| Electronegativity | 3.0 | 2.1 | 2.0 | 1.9 | 1.8 |
| Ionisation enthalpy | High | ↓ | ↓ | ↓ | Lowest |
Why does metallic character increase? As you go down, atomic size increases. The valence electrons are farther from the nucleus and more shielded. They become easier to lose (lower ionisation enthalpy) and harder to gain. So the elements start behaving less like electron-grabbers (non-metals) and more like electron-donors (metals). …