Complex Hexaaminenickel(II)chloride

Hexaaminenickel(II)chloride

Hexaaminenickel(II)chloride is a coordination compound with the chemical formula of [Ni(NH 3) 6 ]Cl2

1.Atomic Structure

Nickel (Ni)

• Atomic Number: 28
• Electron Configuration: [𝐴𝑟]3𝑑84𝑠2[Ar]3d84s2. This means nickel has a core of argon with eight electrons in the 3d orbital and two electrons in the 4s orbital.
• Valence Electrons: The valence electrons for nickel are generally the electrons in the outermost shell, which includes the 4s and 3d orbitals. Since nickel is in the 10th column of the periodic table, it has ten valence electrons: eight in the 3d orbital and two in the 4s orbital.

In this compound, nickel has an oxidation state of +2. When forming the complex ion with ammonia, nickel loses the two 4s electrons, leaving an electron configuration of [𝐴𝑟]3𝑑8[Ar]3d8. The coordination complex forms when six ammonia (NH_3) molecules act as ligands, donating their electron pairs to nickel, leading to a stable octahedral structure.

Chlorine (Cl)

• Atomic Number: 17
• Electron Configuration: [𝑁𝑒]3𝑠23𝑝5[Ne]3s23p5. Chlorine has a core of neon with two electrons in the 3s orbital and five electrons in the 3p orbital.
• Valence Electrons: Chlorine has seven valence electrons (two in the 3s orbital and five in the 3p orbital), which accounts for its high reactivity and tendency to gain an electron to achieve a stable octet configuration.

In this compound, chlorine exists as chloride anions (Cl^-), each with one additional electron in the 3p orbital, completing their octet. This forms a stable electronic structure, balancing the positive charge of the nickel cation in the complex.

Nitrogen (N)

• Atomic Number: 7
• Electron Configuration: [𝐻𝑒]2𝑠22𝑝3[He]2s22p3. Nitrogen has a core of helium with two electrons in the 2s orbital and three electrons in the 2p orbital.
• Valence Electrons: Nitrogen has five valence electrons (two in the 2s orbital and three in the 2p orbital). These five valence electrons give nitrogen its characteristic ability to form covalent bonds.

In this compound, nitrogen is part of the ammonia molecules, acting as ligands for the nickel centre. Each nitrogen atom in the ammonia molecules donates a lone pair of electrons to form coordinate covalent bonds with nickel, helping to stabilize the overall complex.

To give more visual understandings, 3d structure of the complex is shown below:

Picture 1 shows 3d model of Hexaaminenickel(II)chloride

Lime green = Nickel,

Dark green = Chlorine,

Blue = Nitrogen,

White = Hydrogen.

Overall, Hexaamminenickel (II) chloride is a complex compound where nickel is at the centre, surrounded by six ammonia molecules, forming an octahedral structure. The chloride ions serve to balance the charge of the complex. Understanding the electron configuration and valence electrons for each atom provides insight into the stability and reactivity of this coordination compound.

2.trends/ patterns in the properties of the atoms

Nickel

Nickel, Ni is classified as a transition metal. Nickel is characterized by the presence of a partially filled d-subshell in the metal atom and has +2 oxidation states. The partially filled d- orbitals in this compound cause it to exhibit a wide range of colours and leads to interesting magnetic properties. Nickel also has high melting and boiling point which are 1453 melting point and 2732 boiling point

Nickel can form a maximum of six bonds, the electrons must occupy highly delocalized orbitals causing the high electrical conductivity observed in metals. The trends in the chemical properties of the transition metals in each group parallel the changes in atomic and ionic radii.

In the fourth period, the atomic radius decreases fairly rapidly through the element chromium in group six. After chromium, the atomic radius decreases much more slowly and actually increases from nickel to copper. 

Moreover, the properties of nickel are a silvery-white, hard, malleable and ductile metal. Malleable means the property of metal associated with ability to be hammered into a thin sheet without breaking. Meanwhile, ductility is the property of metal associated with the ability to be stretched into wire without breaking. Nickel also a good conductor of heat and electricity. The metal dissolves slowly in dilute acids

Nitrogen

Nitrogen is the member of group 15 (non-metals) in periodic table and it has five valence electrons with the electron configuration ns2np3. Also, this element generally forms compounds with three covalent bonds, leaving one lone pair on the central atom.

When compared with the rest of Group 15, nitrogen has the highest electronegativity which makes it the most non-metallic of the group. The oxidation states of nitrogen are -3, +3 and +5. Nitrogen has -210℃ melting point and -196℃ boiling point comprises 78% (by volume) of the atmosphere, and it is easily isolated by fractional distillation of liquid air.

Nitrogen is second only to sulfuric acid in the quantity produced by the chemical industry. Nitrogen is relatively nonreactive because it exists as nonpolar diatomic molecules containing a strong triple bond (945 kJ/mol). Nitrogen exists in a polyatomic state which is made up of three or more atoms in a stable structure (bound state). Nitrogen react as a gas but as you move down there is a significant increase in the metallic character of the elements.

Hydrogen, H

Hydrogen is literally listed in group 1 on a periodic table. It is not surprising that the lightest element has unique properties. Hydrogen is colourless, odourless gas and it has the lowest density of all gases. Hydrogen has a higher ionization energy than all the elements in Group 1. Also, smallest molecule or atomic size in Group 1 and overall and hydrogen has a higher electronegativity compared to all other elements in Group 1.

-hydrogen can lose an electron to form a proton (H+ (aq) in water) in combination with electropositive metals, it can gain an electron to form the hydride ion, H-, which has the electron configuration of the noble gas helium. With an electronegativity near the middle of the scale. Hydrogen can also form strong covalent bonds with other non-metallic elements. Hydrogen is the most abundant element in universe.

Hydrogen forms covalent hydrides with non-metals but reacts rapidly only with oxygen, fluorine and chlorine. Hydrogen is transparent to visible light, to infrared light and to ultraviolet light to wavelengths below 1800 Å because its molecular weight is lower than that of any other gas, its molecules have a velocity higher than those of any other gas at a given temperature and it diffuses faster than any other gas. Consequently, kinetic energy is distributed faster through hydrogen than through any other gas, for example, the greatest heat conductivity.

Ammonia, NH3

Nitrogen also reacts with hydrogen gas to form ammonia, but only under special conditions. This reaction is known as nitrogen fixation, the combination of the element with another element. Nitrogen fixation is the process by which nitrogen is taken from its molecular form (N₂) in the atmosphere and converted into nitrogen compounds useful for other biochemical processes. Fixation can occur through atmospheric (lightning), industrial, or biological processes.

Biological nitrogen fixation can be represented by the following reaction in which the enzyme-catalyzed reduction of N₂ to NH₃, NH₄⁺, or organic nitrogen occurs:

N₂ + 16ATP + 8e^-           2 NH₃ + 16ADP + 16P­_I + H₂

This process is performed by a variety of prokaryotes, both symbiotic and free living, using an enzyme complex termed nitrogenase that is composed of two separate protein components (dinitrogenase reductase and dinitrogenase).

Nitrogen fixation is the most important reaction of the biological nitrogen cycle. The six-electron reduction of the triple bonds of nitrogen to form ammonia is ultimately favourable and gives off a significant amount of energy. However, in the Born-Haber process, the commercial production of ammonia, the formation of the partially reduced intermediates requires high temperature and pressure.

Ammonia is a colourless gas that condenses at -33℃. The gas has a pungent odour, which is the smell in “smelling salts”. Ammonia also dissolves in water, forming a solution that is often called “ammonia hydroxide”, although NH₄OH has never been isolated. 

3. Chemical Bonds

NH₃ is a covalent bond because nitrogen and hydrogen have shared the electron. Furthermore, nitrogen and hydrogen are both non-metals and do not have the tendency to donate their electrons. Both nitrogen and hydrogen share their electrons to complete the outermost shell and form a stable covalent compound NH₃. 

Nickel, Ni is in Group 10 of the periodic table and represents one of the transition metals. Transition metals are named for their ability to form covalent bonds using electrons from two shells located about the atom’s nucleus.

Chlorine, an electron pair is shared between the two atoms in Cl₂. This is called covalent bonding. So, by sharing electrons through covalent bond formation, atoms are able to fill their valence shell and so attain a noble gas configuration.

Overall, the type of chemical bonds presents in the hexaamminenickel (II) chloride molecule is covalent bonding.

4. How bonds affect the chemical properties

2D picture of Hexaaminenickel(II)Chloride complex

Covalent bonds involve shared electrons, while ionic bonds are result from electron transfer.

Because of that, Hexaaminenickel(II)chloride is anhydrous and cannot dissolve in water.

Hexaaminenickel(II)chloride has a covalent bond which means Van der Waals attraction force exists between molecules.

Other than that, between Chlorine and Nickel, a co-ordinate bonds exist.

A co-ordinate bond is a type of alternate covalent bond that is formed by sharing of an electron pair from a single atom. Both shared electrons are donated by the same atom. It is also called a dative bond or dipolar bond.

5. Usage of hexaaminenickel(II)chloride

Hexaamminenickel chloride, with the chemical formula

[Ni(NH3​)6​]Cl2​

, is a violet solid. It consists of the metal amine complex

[Ni(NH3​)6​]2+

Picture 2 shows solid hexaaminenickel(II)chloride

Where six ammonia ligands are attached to the nickel (II) ion. This complex is paramagnetic due to two unpaired electrons localized on each nickel center. It is prepared by treating aqueous nickel (II) chloride with ammonia and serves as a molecular source of anhydrous nickel (II).

Picture 3 shows Nickel(II)chloride

Additionally, when aqueous nickel chloride precipitates from solution, it carries six water molecules into the crystals, resulting in hydrated solid nickel (II) chloride with the formula.

Generally, we use hexaaminenickel(II)chloride in synthesis and stoichiometric analysis experiment. We can quantify chemical component in a chemical complex using titration method. The results of this experiment give us the empirical formula of hexaaminenickel(II)chloride.

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References

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