Hi friend,
I willl give you general idea but i am not sure it's solution for you.Mercury occurs naturally in the environment and exists in a large number of forms. Like lead or cadmium, mercury is a constituent element of the earth, a heavy metal. In pure form, it is known alternatively as "elemental" or "metallic" mercury (also expressed as Hg(0) or Hg0). Mercury is rarely found in nature as the pure, liquid metal, but rather within compounds and inorganic salts. Mercury can be bound to other compounds as monovalent or divalent mercury (also expressed as Hg(I) and Hg(II) or Hg2+, respectively). Many inorganic and organic compounds of mercury can be formed from Hg(II).

Native Mercury isn't so rare.
http://www.minerals.net/mineral/elements/m...ry/mercury1.htm
http://www.mii.org/Minerals/photomercury.html

Yes, they're both samples of Cinnabar (HgS) However, if you look closely at both images, you should be able to see the little blobs of native mercury that are generally associated with Cinnabar deposits.

As far as Valancy goes generally speaking most elements will react to a point where they have a full or half full shell of electrons.

Taking Cu (I) as an example, the electronic configuration of Cu (0) is [Ar]3d10 4s1
So Cu(I) is formed when Copper looses a single 4s electron to acheive a stable configuration.

IIRC they can also react so that they have pairs of electrons (no odd electrons) so in the case of Cu(II) I think it has an electronic configuration of something like [Ar]3d8 4s2 but i'm not 100% certain on that and I lack the time to look it up.

Heavier Group 18 elements can form compounds because they already have full shells, they have less of a grip on this full shells.

As far as the colour of Gold goes, Theory predicts that Gold should be a similar sort of colour to copper (most of the 'coloured' metals are blueish or reddish). However, applying a relativistic correction to the outer most orbitals shifts the peak and makes Gold appear the colour it does instead of a Ruddier colour.

As far as Mercuruos versus Mercuric chloride goes - Mercurous chloride is unstable, because of the Hg-Hg bond that forms, this bond can be broken by UV light to give Elemental Mercury and Mercuric chloride. I read somewhere that Mercury is unusual in this regard among the Group 12 metals, but I also seem to recall that Cadmium can also form a Dimer ([Cd-Cd]^2+) but it takes some 'persuasion' to do so).

It's a lot to wade through, but the article is interesting:

http://en.wikipedia.org/wiki/Atomic_orbita...ivistic_effects

"Relativistic effects
For elements with high atomic number Z, the effects of relativity become more pronounced, and especially so for s electrons, which move at relativistic velocities as they penetrate the screening electrons near the core of high Z atoms. This relativistic increase in momentum for high speed electrons causes a corresponding decrease in wavelength and contraction of 6s orbitals relative to 5d orbitals (by comparison to corresponding s and d electrons in lighter elements in the same column of the periodic table); this results in 6s valence electrons becoming lowered in energy.

Examples of significant physical outcomes of this effect include the lowered melting temperature of mercury (which results from 6s electrons not being available for metal bonding) and the golden color of gold and caesium (which result from narrowing of 6s to 5d transition energy to the point that visible light begins to be absorbed)."

And:

http://www.fourmilab.ch/documents/golden_glow/

"The colour of metals such as silver and gold is mainly due to absorption of light when a d electron jumps to an s orbital. For silver, the 4d→5s transition has an energy corresponding to ultraviolet light, so frequencies in the visible band are not absorbed. With all visible frequencies reflected equally, silver has no colour of its own; it's silvery. In gold, however, relativistic contraction of the s orbitals causes their energy levels to shift closer to those of the d orbitals (which are less affected by relativity). This, in turn, shifts the light absorption (primarily due to the 5d→6s transition) from the ultraviolet down into the lower energy and frequency blue visual range. A substance which absorbs blue light will reflect the rest of the spectrum: the reds and greens which, combined, result in the yellowish hue we call golden. "