Answer:
That would be helium, with a melting point of 0.95 K (-272.20 °C)—although this happens only under considerable pressure (~25 atmospheres). At ordinary pressure, helium would remain liquid even if it could be chilled to absolute zero.
Answer: The child isotope has an atomic mass of 206.
Explanation:
Alpha decay : When a larger nuclei decays into smaller nuclei by releasing alpha particle. In this process, the mass number and atomic number is reduced by 4 and 2 units respectively.
General representation of an element is given as: 
where,
Z represents Atomic number
A represents Mass number
X represents the symbol of an element
General representation of alpha decay :


What u need ????? Help on Doing ?
Density is equal to the ratio of mass to the volume.
The mathematical expression is given as:

Arrange the above expression in terms of volume, i.e.

Density of osmium is equal to =
Mass of osmium = 4.80 kg
First, convert the mass in kg to g:
1 kg = 1000 g
Therefore, mass in g =
= 4800 g
Put the values,

=
.
Hence, volume occupied by osmium =
.