What defines density of matter?

[Moreno]

Why Radon is gas under ambient temperature, but Gold and Lead are solid bodies? Even though Radon atoms are heavier.

[Strange]

Radon is one of the "noble gases". These have no valence electrons available for forming bonds with other atoms. This means that the radon atoms are not bound to one another as gold or lead are in the solid form.

[studiot]

Radon is a member of the noble or inert gases group (Helium, Neon, Argon, Krypton, Xenon and yes Radon is the 'heaviest')

This group is called noble, like gold or platinum because it is chemically unreactive.

In fact the atoms of the group are even more unreactive than gold or platinum so are also called inert.

inert means that the atoms are very reluctant to react with any other atoms, even another noble gas atom.

To form a solid they must react with several other atoms to form the links in the solid crystal.

This only happens at very low temperatures and/or very high pressures.

About the only atoms they will react with at normal laboratory conditions is Flourine, the most reactive element.

So there you have it immovable object v irresistible force.

Edited November 23, 2019 by studiot

[Moreno]

Why Nitrogen is a gas, but Copper is a solid? Nitrogen is three-valent and Copper is monovalent. Doesn't in mean Nitrogen does have more bonds to form and potentially more likely to form a crystal structure?

[mistermack]

4 hours ago, Moreno said:

Why Nitrogen is a gas, but Copper is a solid?

Not necessarily. Nitrogen can be a liquid, and so can Copper. It depends on temperature and pressure. So what you are really asking, is why they have different boiling and melting points. 

Can't help you on that. Something to do with the intermolecular forces. 

[Sensei]

41 minutes ago, mistermack said:

Not necessarily. Nitrogen can be a liquid, and so can Copper. It depends on temperature and pressure. So what you are really asking, is why they have different boiling and melting points. 

Can't help you on that. Something to do with the intermolecular forces. 

Water is good example of intermolecular forces. Is has mass just ~18.016 u, when air gases Oxygen has mass ~ 32 u (~80% more), and Nitrogen has mass ~28 u (~50% more). Why isn't water gas like Oxygen and Nitrogen? Because it is polar molecule i.e. it has not uniformly placed electrons, and one water molecule bonds with other water molecules around it (forming weak Hydrogen-bonds).

https://en.wikipedia.org/wiki/Hydrogen_bond#Water

Yet another related subject is hydrophilic and hydrophobic properties of molecules.

https://en.wikipedia.org/wiki/Hydrophile

https://en.wikipedia.org/wiki/Hydrophobe

(typically polar and nonpolar molecules)

Edited November 24, 2019 by Sensei

[studiot]

10 hours ago, Moreno said:

Why Nitrogen is a gas, but Copper is a solid? Nitrogen is three-valent and Copper is monovalent. Doesn't in mean Nitrogen does have more bonds to form and potentially more likely to form a crystal structure?

 

5 hours ago, Sensei said:

it has not uniformly placed electrons, .......................................

..................(typically polar and nonpolar molecules)

 

5 hours ago, mistermack said:

Not necessarily. Nitrogen can be a liquid, and so can Copper. It depends on temperature and pressure. So what you are really asking, is why they have different boiling and melting points. 

 

 

Excellent points +1 each

It is instructive to consider this question in relation to the (usual form) periodic table.
Here are two showing melting and boiling points.

Can you see any pattern of clustering of solids, liquids and gases?

Note that the alkali metals alkaline earths  on the left are solids, whereas the elements near to inert gases on the right are often gaseous or liquid.

But both Flourine and Lithium are the most reactive elements and head groups of high reactivity.

This suggests two different types of reaction.
And this is indeed the case and the reason why the state of an element does not depend on valency.

The alkali metals can move towards an inert gas electron structure by donating an electron and becoming a positive ion, thus  forming ionic bonds.

The halogens move towards an inert gas configuration by gaining an electron and becoming negative ions which can participate in ionic bonds.

Elements between these extreme tend to form covalent bonds and metals tend to join together to form metallic bonds.