A noble gas is an element in Group 18 of the periodic table with a stable, full outermost shell, so it is chemically inert and exists as single atoms.
A noble gas is an element in Group 18 of the periodic table with a stable, full outermost shell, so it is chemically inert and exists as single atoms. Malay: gas adi · Chinese: 稀有气体.
Helium, neon and argon are the noble gases you meet most. Their defining feature is a complete outer shell, eight electrons for neon and argon (an octet), and two for helium (a duplet), which is already the stable arrangement that other atoms react to reach. Because a noble gas has nothing to gain from losing, gaining or sharing electrons, it does not readily form compounds. That is why they are described as inert, why they exist as single, separate atoms (they are monatomic rather than diatomic), and why they were the last main group to be discovered.
Example. Helium is used to fill balloons and airships because it is light and does not burn; argon fills light bulbs and is used to shield welding because it will not react with the hot metal; neon glows red-orange in advertising signs. In each use the point is the same, the gas is chosen precisely because it does not react.
Confusion to avoid. “Inert” does not mean the atoms are not there or do nothing physically; it means they are chemically unreactive. Do not say a noble gas has “no electrons in its outer shell”, the opposite is true, its outer shell is full. And a full shell of eight is an octet, while helium’s full shell of two is a duplet, so do not force helium to have eight.
In the Periodic Table of Elements chapter the noble gases explain why every other element reacts at all: atoms of other elements gain, lose or share electrons in order to reach the same stable, noble-gas arrangement.
Want a teacher to make this click?
We teach SPM Chemistry one to one, so your child understands it and scores it.
from RM50/hr · One-hour paid trial · Same-day reply