Here, average radius of sodium atom,r=2.5Å=2.5×10–10m
∴ Volume of sodium atom =

4

3

πr3
=

4

3

×3.14×(2.5×10−10 )3
=65.42×10−30 m3
Mass of a mole of sodium =23 gram
=23×10−3 kg
Also we know that each mole contains 6.023×1023 atoms, hence the massof sodium atom,
M=

23×10−3

6.023×1023

kg
=3.82×10−26 kg
∴ Average mass density of sodium atom.
ρ=

M

V

=

3.82×10−26

65.42×10−30

kg m−3
=0.58×103 kg m−3
Density of sodium in crystalline phase =970k gm–3=0.970×103kg m–3
∴

‌Average‌mass‌density‌of‌sodiumatom

‌Density‌of‌sodium‌in‌crystalline‌phase

=

0.58×103

0.970×103

=0.66
Yes, both densities are of the same order of magnitude, i.e. of the order of10‌3.
This is because in the solid phase atoms are tightly packed.