Gold Structure, Characteristics:31 Complete Quick Facts


In this article, we discuss a rare transition metal gold structure and its 31st characteristics. Let’s talk about the expensive transition metal gold and its important facts.

Gold is a common chemical name its Latin name is Aurum and denoted by Au. Gold is d block transition group 11th element. It is a 5d element and due to transition metal gold structure shows metallic property and it obeys the crystal field theory. In gold structure, there is 6s orbital is present and due to the 6s orbital, it shows abnormal behavior which comes from relativistic contraction.

The electronic configuration of gold structure is [Xe]4f145d106s1, so the most stable oxidation form of gold is Au(III) because in that form it has complete f orbital and gains the most stable form. Gold can form different organometallic molecules as its bonding is quite similar to 3d elements.

Some important facts about gold

Gold is present in the earth’s crust so, it is extracted mainly cyanide process. The gold ore goes through dilute sodium cyanide solution to make the alkaline with lime water presence of air for oxidation purposes.

4Au + 8NaCN + 2H2O +O2 =  4Na[Au(CN)2] + 4NaOH

The solution is then filtered and gold is deposited from the filtrate by zinc shavings.

Zn +2Na[Au(CN)2] = 2Au + Na2[Zn(CN)2]

The zinc is dissolved out by dilute sulfuric acid and then it dried residue of gold is melted under the borax.

The crude gold is not pure, it contains copper, silver, and sometimes lead also. The lead part is removed by the process called cupellation. The copper part is removed by oxidative fusion with borax and nitrate. The silver part may be removed by boiling with concentrated sulfuric acid up to when silver is deposited.

The best method to extract gold from crude is electrolytic refining using a solution of HAuCl4 and crude gold deposit at an anode.

Amalgamation is also a method to separate the native gold from alluvial sand. In this method, we separate the mercury part from the alluvial sand to get pure gold.

The melting point and boiling point of gold are 1337.33 K and 3243 K respectively. Due to heavy metals, the energy required for breaking the interstitial bond is high. The color of gold is metallic yellow. Its ΔH atomization is 380 KJ/mol. The density of gold is 19.32 g/mol so we can see that it is a much heavier element.

The electrical resistivity at 200C is 2.35 ohm-cm. the electronegativity is 2.4 at the Pauling scale so it is seen that gold has an affinity toward electronegativity, as Au is stable due to a complete 6s orbital. The first, second, and third ionization energy of a gold structure is 890, 1973, and 2895 kJ/mol as electrons are released from s, d orbitals.

1.    What is the gold structure?

The gold structure is FCC (face-centered cubic), in the solid-state which is also known for its characteristic color. Even the metallic yellow color of the gold structure arises due to absorption in the near UV region.

gold structure
Lattice Structure of Gold

The color of the gold structure is for the excitation of electrons from the d band to the s-p conduction band which is absorbed in the blue region of color. In the FCC structure, net number of atoms = 8*1/8 +6*1/2 =1+3 =4.

In the FCC structure, we know the , so % of occupied space = (4*4/3πr3)/a3 *100

So, for FCC % of occupied space is 74.05%, so the % of void space is 25.95 and it is proved that FCC is the most tightly packed cube system.

2.    Is gold a transition metal?

Gold is group 11th element and belongs to the d block 5d element, so gold is a transition metal. Transition metals are those which have partially filled or filled d electrons in any oxidation state. From the electronic configuration of gold, it is evident that it has filled 5d orbitals, and up to +1 oxidation state, its d orbital is filled.

As gold is a transition element then it shows transition metal properties like CFT. The most stable oxidation state of the gold structure in bond formation is +2. The +2 oxidation state of the gold structure is the d9 system and shows different CFT properties.

In the gold structure, Crystal field theory gold is splitting in square planner geometry. Because gold has filled d electron and f electrons also, for those electrons the effective nuclear charge of Gold structure is highly increased and the interaction between gold and other ligands also increases in such a way that gold structure split in a square planner manner. Actually, the CFT value is increasing from 3d-4d-5d orbitals.

CFT of Au(II)

There are five subsets in d orbitals, they are dxy, dyz, dxz, dx2y2, and dz2. These five sets are categorized in two different forms according to their energy. First, three are called t2g, and later two are called eg. the eg set of orbitals are directly involved in the bond formation with ligands, so eg has higher energy than t2g.

The electronic configuration of the gold structure is, [Xe]4f145d106s1, so in Au(II) two electrons lacking from the gold structure, and gold releases one electron from the  6s orbital and another one from the 5d orbital. So now in 5d orbitals, there are nine electrons in Au(II) system.

Those nine electrons are arranged in the five subsets, so the last subset of dx2y2 gets only one electron and the other gets paired. Now in the crystal field theory, the energy difference between t2g and eg is called the 10Dq value, by this value, we can predict the stability of the gold structure.

After full splitting, the energy of dxy will energize in such a way that it crosses the barycentre and reaches dx2y2. So, now the energy difference between  dx2y2 and dxy is equal to the 10Dq value.

The energy of each t2g orbital is -0.4Δ0 and the energy of each orbital of eg is -0.6Δ0. only these two orbitals are contributed to the crystal field stabilization energy because other orbitals do not contribute toward the 10Dq value. There is one electron in dx2y2 orbital and two electrons in dxy orbital. So, the net crystal field stabilization energy of gold structure in its +2 oxidation state is, 1*(-0.6Δ0) + 2*(-0.4Δ0) = -.2 Δ0. The negative sign indicates the stabilization of the gold structure.

Gold structure always forms a low spin complex with any kind of ligands. Because the effective nuclear charge is higher for gold structure due to the presence of d and f electrons and for this reason metal- ligands interaction will be high and therefore the Δ0 value also increases and the complex formation occurs with a low spin of the metal center.

Au(II) complexes are a d9 system having 2-fold ground state degeneracy, hence it is subject to extensive tetragonal distortion according to the Jahn teller theorem and by s-d mixing it will be elongated- the complex becomes a square planner. In this square planner geometry, the Δ0 value is very high and it is, and for this reason, the sole electron from the dx2-y2 orbital may be readily lost – leading to the formation of Au(III) complex – the process leads to a decrease in energy in splitting diagram.

The electron lost from one Au(II) complex molecule may be readily accepted by the neighboring complex Au(II) molecule, the latter is reduced to a corresponding Au(I) complex. This process is also favored since there will be an additional stabilization of the d10 configuration which is exchange energy. Thus the net reaction is the disproportionation of Au(II) complex from Au(I) and Au(III).

3.    Is gold a compound?

Gold is a transition metal and a group 11th element, but it can form different compounds because it can show different oxidation states.

Au(III) compound

In gold structure, Au(III) is the most common oxidation state of golf, in this oxidation state it can form different binary compounds and complexes.

Au2O3.H2O is brown-colored amorphous precipitated by the reaction of alkali from the solution which contains AuCl4. The nature of the complex is amphoteric, which can dissolve in excess alkali or acid into an anionic complex.

Au(OH)3 + NaOH = Na[Au(OH)4]

Au(OH)3 + 4HNO3 = H[Au(NO3)4] + 3H2O

From the hydrated compounds, an anhydrous oxide is may be obtained by carefully heating with P4O10. It can be decomposed above the temperature of 1600C to Au2O and gold. The crystal structure of the AuO4 complex is square planar sharing with oxygen.

Another molecule Fulminating gold is an olive-green color that is explosive powder. The molecule is obtained by the digestion of Au2O3 or any hydrate reaction with ammonia. this dry powder can explode with fulminates on heating and the possible composition is HN=Au-NH2. 1.5H2O.

The sulfur-containing gold molecule is Au2S3 is cannot be obtained from the aqueous solution because it is decomposed by the water. It is prepared another method by passing through H2S gas over the dry LiAuCl4.2H2O at a very low temperature.

2liAuCl4 + 3H2S = Au2S3 + 2LiCl + 6HCl

That LiCl can be separated by the extraction with an a basic solution and the black powder is dried at moderate temperature.

The fluoride of gold, specifically Au(III) with fluorides is prepared by the reaction of elemental fluorine on Au2Cl6 at a very high temperature like 3000C.

The reaction goes as sequences like,

Au(III) Complex Formation

AuF3 is a crystal of orange color and it can decompose at 5000 to gold and elemental fluorine. The crystal structure is a square planar shape with cis fluorine atoms in the helical chain. The terminal Au-F bond distance is lower than the bridge Au-F bond.

Au2Cl6 molecule is red in color and it can be directly synthesized by refluxing HAuCl4 with thionyl chloride.

2H3O+AuCl4 + 2SOCl2 = Au2Cl6 + 2SO2 + 6HCl

The structure of the dimeric molecule is planar and it is a diamagnetic complex in the solid as well as vapor phase also.

Dimeric Structure of AuCl3

Au2Cl6 can dissolve in hydrochloric acid to form chloroauric acid. The evaporation of HAuCl4 gives a yellow-colored crystal of H3O+AuCl4.3H2O. NaAuCl4.2H2O and KAuCl4 both gold (III) salts are water-soluble.

Au(II) compound

In the gold structure, Au(II) is an unfavorable oxidation state as compared to Au(I) and Au(III). Au(II) complexes are very rare. There are many examples of Au(II) complexes but they are mixed oxidation states of the gold structure.

In dinuclear compounds, we can find the Au-Au bonds in gold structure which may be formed by the oxidation addition of the Au(I) complex.

Au(II) Complex

Here the main driving force of the Au(II) complex is the bidentate phosphine ligands hold two gold atoms in close range in rigid conformation.

Au(I) compound

Only a halogenated molecule is observed for Au(I) state. But sometimes a violet-grey colored molecule named Au2O has obtained by the process of dehydrating AuOH, but the authentication of this molecule is not confirmed.

Au2S appears dark brown in color and is precipitated by the saturation of a solution of Kau(CN)2 with hydrogen sulfide gas, followed by the addition of hydrochloric acid. This is insoluble in water and in dilute acids too. But it can dissolve in the aqua regia and aqueous KCN. It is also soluble in excess sodium sulfide solution.

4.     Is gold inorganic or organic?

Gold is an element and it is not formed via hydrocarbon. In the gold structure, we can see that there are d electrons present. Which makes gold a transition metal. Metal cannot be an organic molecule.

When gold forms different kinds of molecules in the gold structure they are forming via electrostatic interaction of different oxidation states of the gold structure. So, all the gold compounds are inorganic. Gold is a 5d element, so the effective nuclear charge is very high and there is no possibility of hybridization of gold structure. Gold has a higher coordination number according to its respective oxidation state.

So, the molecule of gold is not covalent, although gold can form different organometallic clusters by the reaction with different π-acidic ligands, the nature of the complex is low spin in the gold structure. The electronegativity of gold structure is so high and the electron affinity also for gold is very high, so it can be ionized when a gold molecule is formed.

So, gold is an inorganic substance when it forms chloride or any other salts.

5.    Is gold an element?

The elemental form of gold is Au. It is a d-block element, especially a heavier metal. The elemental form does not change when it shows a different oxidation state the respective charge is placed above the element.

The atomic number of gold is 79 which means it is the 79th element in the periodic table.

6.    Is gold an isotope?

Two or more species of the same elements having the same atomic number but differing in atomic mass is called the isotope of the first element. Isotopes have the same or nearly the same chemical behavior but their physical property may be different.

The mass number of gold is generally 197 and the isotope having 195 mass number is the stable isotope of Au. Apart from them, gold has 36 radioactive isotopes, but radioactive isotopes have a short life span. 195Au has the highest half-life among the other isotopes of gold. The half-life of that isotope of gold is 186 days.

Half-life is the time for elements how much time required for its half of the portion will be dissociated. If we consider 100% of the isotopes then after 186 days it remains only 50% of it, the rest 50% are dissociated and it takes 186 days for the dissociation.

Isotopes are born for some nuclear fission and nuclear fusion process. Sometimes α and β decoys are also responsible for the formation of isotopes. Gold is a heavier element and it can dissociate with different small elements by accepting suitable energy, so it has more number of isotopes. The higher the number of atomic mass higher will be the number of isotopes, but in the case of hydrogen it has three isotopes but the mass number is 1 for hydrogen. So exceptional cases are always present.

The nature of α and β decoys can decide that how many isotopes are radioactive or how many are stable. Gold is a 5d element and it is a later element in the periodic table and near to radioactive elements, so it has many more radioactive isotopes.

7.    Is gold on the periodic table?

Every metal or every element in chemistry should have a particular position in the periodic table. Gold is present in the 11th group 6th period and d block element.

Gold is a transition metal and it is a 5d element which means it has a d orbital and the valence electrons should be contained in the d orbital. As it is a 6th-period element so there is an involvement of 6s orbital for gold structure. The electronic configuration of the gold structure is, [Xe]4f145d106s1.

Due to the involvement of the 6s orbital its shows relativistic contraction and for this reason its shows different abnormal behavior. Due to the presence of d and f orbital, it has a poor screening effect.

The outermost electrons of an atom experience two types of forces- nuclear attraction force and repulsion with the inner electrons. It is due to the second force that the outermost electrons cannot experience the total nuclear charge but only apportion of it known as an effective nuclear charge. In fact, the inner electrons practically behave as a screen between the nucleus and the outermost electron- the phenomenon refers to as the screening effect.

The greater the penetrating power of an orbital better will be the extent of screening of the orbital electron density. Since the order of orbital penetratively hence s>p>d>f. hence the order of screening is also be s>p>d>f.

In fact, it is due to the greater diffuseness of the electron density in that d and f orbitals they exhibit a poor screening effect.

With the screening effect and relativistic contraction of several properties of the gold are altered.

Down the group from Copper to silver the principal quantum number increases but the configurations are similar. Thus as expected the ionization energy decreases with an increase in principle quantum number. In the case of gold it is due to the extensive relativistic contraction of the 6s orbital that the nuclear attraction for the outermost 6s electrons increases.

Also, it is due to the relativistic contraction of 6s and 4f orbitals being subject to relativistic expansion- screening by the 4f orbitals becomes even poorer  – effective nuclear charge increases to a large extent. Thus the relativistic contraction of 6s orbital couple with f contraction accounts for the extremely high nuclear attraction for 6s electrons.

This factor highly predominates over the effect of an increase in principle quantum number from Ag to Au. Thus ionization energy of gold structure much much higher than Ag.

From the electronic configuration of gold, it is evident it is due to the presence of 14 4f electrons the effective nuclear charge of gold structure increases to such an extent that its electron affinity becomes extremely high.

For Au, the electron will be accepted in the 6s orbital. Since the 6s orbital is subject to relativistic contraction. Its energy decreases and becomes so low as compared to that of 6p that the 6p orbital practically behave as post valence orbital.

Thus, the configuration of Au is practically the filled one comparable to those of noble gases- hence the name noble liquid configuration. Thus, to attain the noble liquid configuration gold will accept an electron readily – the electron affinity of gold is extremely high.

CsAu is a stable molecule and it is an example of the abnormal behavior of gold in the periodic table.

Cs is an alkali metal having only one electron in the outermost shell. Also, it is due to the larger size of cs the nuclear attraction for the outermost electron is extremely low. Thus first ionization of Cs is low. Cs can readily lose an electron (undergoes ionization) – the electron lost can be readily gained by Au since the electron affinity of Au is extremely high due to the above reasons.

Aurophilicity

The au atoms have been found to have weak interactions with the neighboring Au atoms- Aurophilic interaction. The major cause for this interaction is that each of the Au atoms has an inherent tendency to accept an electron, in order to assume the noble liquid configuration. Thus in an effort to attain the noble liquid configuration, each Au atom will try to draw electron density with neighboring Au atoms – thereby leading to interaction (Aurophilic interaction) between them, and the phenomenon is referred to as Aurophilicity.

8.    Is gold polar or nonpolar?

It is very difficult to say for an element is polar or nonpolar in nature. Polarity arises due to the resultant dipole-moment value. Again, for a molecule, if the electronegativity difference is so high then we can say the molecule will be polar.

In the gold structure, there is no factor present which makes the gold polar or maybe non-polar. The electronegativity of gold is very high, but there must be some elements present so we can compare the difference. In the elemental state, this comparison is not allowed. When gold is making a molecule in its most stable oxidation state in the +3 oxidation state, it generally formed halogenated molecules.

Halogens are most electronegative so there is a chance of higher electronegativity difference and the shape of the molecule is asymmetric because there is an odd number of atoms that will be present as gold is in a +3 oxidation state. So there may be a chance of getting some resultant dipole-moment and making the molecule polar.

But in elemental form gold structure is non-polar. When gold behaves as an anion the size of that anions are very large and it can be polarizable by any cation and then it may be polar.

9.    Is gold diatomic?

In the elemental state, the gold structure is exhibited as Au, so it is monoatomic in nature. All the metal atoms are monoatomic.

Metal atoms are mostly electropositive and due to higher electropositivity if they exist as the diatomic form then there will be extensive repulsion between two same electrostatic forces. Again, one metal can easily release the electron but that electron accepted by another one is very difficult. Because most the metal has lower electron affinity.

But in the case of gold structure, the electron affinity is higher so it can readily accept the electron from other gold and form a noble liquid configuration. That’s the reason there is aurophilicity observed for the gold structure. Due to aurophilic interaction, there is small interaction occurs but they cannot exist as diatomic form due to their larger size.

10. Is gold magnetic?

Pure gold does not stick to the magnet but if there is some allow present in it then it can be stuck to the magnet. The magnetic property of gold is considered by the electrons in the valence shell.

All the metals are magnetic in nature mat be diamagnetic or paramagnetic depending upon the different oxidation states also.

11. Is gold diamagnetic?

The electronic configuration of the gold structure is [Xe]4f145d106s1. So from the electronic configuration, we can say that there is one unpaired electron present in the 6s orbital of the gold structure. So, in neutral state gold is diamagnetic in nature.

For any metal or atoms, if all the electrons are paired in the form then it is called paramagnetic and if at least one unpaired electron is present then it is called diamagnetic.

For a neutral gold structure, there is only one unpaired electron is present so it is diamagnetic. But the most stable oxidation state is +1 for gold structure. In Au(I) form all the electrons in the 5d and 4f orbitals are paired in form, so in that state gold is paramagnetic.

Again, in the +3 oxidation state, two electrons were removed from 5d orbitals, and according to Hund’s rule, there are two subsets containing two unpaired electrons and making gold diamagnetic.

We can calculate the magnetic value of a diatomic substance by using the number of unpaired electrons.

12. Is gold soluble?

Gold is soluble in the following reagents,

  • aqua regia
  • the mixture of nascent chlorine
  • solutions of nitrates, sulfates e.g. bisulfate of soda
  • strong acid like hydrochloric acid

13. Is gold water-soluble?

any transition metal is insoluble in water, so gold also insoluble in water. Actually, it does not react with oxygen, air, or any kind of liquid except aqua-regia. So, there is no chance for gold to be soluble in water.

14. Is gold conductive?

Any metal is a good conductor of heat and electricity. So gold is also a good conductor of heat as well as electricity.

15. Is gold electrically conductive?

Gold is an electrically conductive agent. Because gold is a metal and for every metal, there is the difference between the conduction band and valence band is very low. Electrons from the conduction band to the valence band are easily transferred and required lower energy for this reason the mobility of ions increases and for this reason, they can conduct electricity in a faster way.

When gold is in an ionic form that is when it exists in a +1 or +3 oxidation state then the electrical conductivity also increases and for this reason it can be disproportionate to the lower oxidation state.

16. Is gold a mineral?

Minerals are those which is naturally occurring in the crystalline solid forms, they are created by the humans or animals’ dead bodies and form a crystal structure. On the other hand, earth metals are those found in the earth’s crust in crystalline form. So basically gold is a mineral and metal both. But gold is not an ore.

17. Is gold malleable?

yes, gold is extremely malleable. Among all the metals only gold is malleable. It can be beaten out into sheets of about 5*10-5 mm thickness. For this malleability, it is used in ornaments. Different types of ornaments are formed by using this property. Among all the versions 18 carat is the least malleable version of gold and the highest is 24 carat. It depends upon how many impurities should be added.

18. Is gold brittle?

Yes, gold is brittle and one gram of gold is beaten to make 24 mm sheets.

19. Is gold ductile?

All the metal has the property of ductility. Gold is a transition metal so yes gold is ductile. From one ounce of gold to 80 km of gold, wire making is possible.

20. Is gold dense?

Yes, gold is a very denser element. The density of gold is 19.32 g/mol that why it is called heavy metal.

21. Is gold heavier than silver?

Yes, gold is much heavier than silver. The density of gold is almost twice the density of silver.

22. Is gold stronger than iron?

The unalloyed and pure iron is much stronger than gold.

23. Is gold lighter than water?

Gold is metal and obviously, it is not lighter than water. It is almost 19 times heavier than water.

24. Is gold hard or soft?

Pure gold is very hard but when it is mixed with impurity or alloy then it becomes soft.

25. Is gold endothermic or exothermic?

The process of solidifying gold is exothermic.

26. Is gold hydrophobic?

On the gold surface, there is some impurities are present like carbon and for this reason, gold is hydrophoure but clean gold is hydrophilic.

27. Is gold transparent?

The density of gold is very high and for this reason gold is opaque, it is not transparent.

28. Is gold crystalline or amorphous?

The gold structure is a face-centered cubic structure, so it is crystalline solid.

29. Is gold radioactive?

Gold has 41 isotopes only one is stable and the rest of all are radioactive.

30. Is gold reactive?

The gold structure is one of the noblest in the periodic table and it is generally an unreactive element.

31. Is gold stable or unstable?

Gold has radioactive isotopes and those isotopes are very reactive but the normal isotope is stable.

Conclusion

Gold is a very malleable and stable element.  For its 6s and 4f orbital, it shows abnormal behavior. The brittleness of gold is very high that’s why it is used for making ornaments. The medicinal chemistry of gold is well known. Different kind of drug is made from gold.

Biswarup Chandra Dey

Chemistry is not all about reading line by line and memorize, it is a concept to understand in easy way and here I am share with you the concept about chemistry which I learn because knowledge is worth to share it.

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