Question

Out of phosphorous, sulphur and krypton the elements having the lowest and highest atomicities are respectively_______________and__________.

Answer 1

Hint:As we already know that atomicity is defined as the number of atoms present in a molecule of an element. Atomicity can be calculated by the ratio of the molecular mass to the atomic mass of an element.

Formula used: $Atomicity = \dfrac{{Molecular\;{\text{mass}}}}{{Atomic\;mass}}$

Complete answer:
We all know that atomicity is defined as the number of atoms present in a molecule of an element and it can be calculated by the ratio of the molecular mass and atomic mass of an element. It can be divided into the following categories:
1. Atomicity of monatomic molecules: The molecules that contain only 1 atom are monatomic like Xenon, Neon etc.
2. Atomicity of diatomic molecules which contains 2 atoms like oxygen, nitrogen, fluorine, chlorine etc.
3. Atomicity of triatomic molecules that possess 3 atoms in molecules like ozone (\[{O_3}\]).
4. Atomicity of tetratomic molecules possessing 4 atoms like Phosphorus.
5. Polyatomic molecules contain more than 4 atoms like sulphur.
As we know that Krypton is a noble gas belonging to group 18 of the periodic table therefore are monatomic molecules and hence its atomicity is 1. Also we can calculate the atomicity by the ratio of its molecular mass and atomic mass which will be:
$Atomicity = \dfrac{{Molecular\;{\text{mass}}}}{{Atomic\;mass}}$
$Atomicity\;of\;Kr = \dfrac{{84}}{{84}} = 1$
Similarly we can find the atomicity of phosphorus which is a tetratomic molecule possessing 4 atoms. Its atomicity is 4 which can be confirmed by using the formula:
$Atomicity = \dfrac{{Molecular\;{\text{mass}}}}{{Atomic\;mass}}$
$Atomicity\;of\;P = \dfrac{{4 \times 31}}{{31}} = 4$
We can calculate the atomicity of sulphur also and we know that is a polyatomic molecule containing 8 atoms so let us calculate its atomicity:
$Atomicity = \dfrac{{Molecular\;{\text{mass}}}}{{Atomic\;mass}}$
$Atomicity\;of\;S = \dfrac{{8 \times 32}}{{32}} = 8$

Therefore we can say that out of these three elements with lowest atomicity is Krypton and element with highest atomicity is Sulphur.

Note:
 Some interesting facts:
1. ${S_8}$is called octasulfur and it is actually not produced as it is but elemental sulphur has it as the main component and it is recovered from volcano sources.
2. Allotropic forms of phosphorus are red, white, black and violet phosphorus. White phosphorus glows in the dark and red one is found on the side of matchboxes we use.
3. Krypton is one of the rarest gases found on earth and is most expensive.