In this article, “n2h4 lewis structure”, different facts on hydrazine like lewis structure drawing, calculation of formal charge, valence electrons, lone pairs, polarity with some relevant topics are discussed briefly.
N2H4or hydrazine is an inorganic colourless and flammable liquid compound having ammonia like odour. It has a molar mass 32.0452 g/mol and density 1.021 g/cm3. The N-N single bond distance is 1.45 A0 having a pyramidal geometry. Hydrazine is a water-soluble compound. It is a polar compound having a permanent dipole moment.
Let’s highlight the following facts on hydrazine (N2H4).
How to draw N2H4 lewis structure?
Lewis structure is a molecular structural representation showing lone pairs or nonbonding electrons around the atoms.
- Determining the valence electrons: Due to having a significant role of valence shell, finding out the number of valence electrons is the most important factor. The constituent atoms, nitrogen and hydrogen have five and one electrons in their respective valence shell.
- Finding out the bonding electrons: The two nitrogen atoms are bonded with each other by one single bond and four hydrogen atoms are also attached with two nitrogen atoms through four sigma bonds. Therefore, total bonding electrons are (5×2) = 10
- Finding out the nonbonding electrons: In hydrazine, only nitrogen contains nonbonding electrons or lone pair. Each nitrogen atom has two nonbonding electrons.
N2H4 Lewis Structure Shape
Molecular shape can only be determined if the hybridization of the central atom is known because the hybridization decides the geometry of any molecule like-
| Hybridization of central atom | Geometry |
| sp | Linear |
| sp2 | Planar |
| sp3 | Tetrahedral |
| sp3d | Trigonal bipyramidal (TBP) |
| sp3d2 | Octahedral |
The above table only will be followed if no repulsive factors are present. The repulsion can be created by the presence of lone pair-lone pair, lone pair-bond pair and bond pair-bond pair repulsion present in the molecule.
In hydrazine, nitrogen is central atom and both the nitrogen is sp3 hybridized having a pair of nonbonding electrons in each of the nitrogen. According to the above table containing hybridization and its corresponding structure, the structure or shape of N2H4 should be tetrahedral. But due to presence of nitrogen lone pair, N2H4 faces lone pair-lone pair and lone pair-bond pair repulsion and thus its molecular shape is distorted from its geometrical or ideal structure. The shape of hydrazine is trigonal pyramidal (ammonia like structure).
N2H4 Lewis Structure Formal Charge
In a molecule, the charge in each of the constituent atom are called as formal charge. Determining the most stable lewis structure is one of the significant use of calculation of formal charge.
- Formal charge = Total number of valance electrons – number of electrons remain as nonbonded – (number of electrons involved in bond formation/2)
- Formal charge of each of the nitrogen atom = 5 – 2 – (6/2) = 0
- Formal charge of each of the four hydrogen atoms = 1 – 0 – (2/2) = 0
From the formal charge calculation, it is clear that none of the constituent atom carry any charge in hydrazine.
N2H4 Lewis Structure Angle
Hybridization also determines the angle between two bonds or the angle containing central atom and its two substituent atoms in any molecule. Every bond angle is constant with corresponding to each of the hybridization if no repulsion is present in that molecule.
As N2H4 is a sp3 hybridized molecule, the ideal bond angle should be 109.50. But due to facing repulsion involving lone pair and bond pair, the bond angle in hydrazine is slightly deviated from the actual bond angle. The bond angle shows the value between 1070– 109.50(bond angle of ammonia 1070) because of the presence of lone pair-bond pair and lone pair-lone pair repulsion which decreases the bond angle from ideal. Thus, this deviation occurs.
N2H4 Lewis Structure Octet Rule
Octet rule states that atoms gain such electron configuration in their respective valence shell through sharing (covalent compound) or complete transferring (ionic compound) which matches with their nearest noble gas electron configuration (complete shell configuration).
Hydrazine is such type of molecule in which, all the constituent atoms obey octet rule. Nitrogen has five outer most shell electrons and when it forms bond with one nitrogen and two hydrogen atoms, it gains three more electrons in its valence shell. Therefore, the number of electrons in its valence shell (5+3) =8, which resembles with the electron configuration of its nearest noble gas, neon (2s2 2p6).
Hydrogen does not follow octet, rather it follows duplet, having two electrons in its valence shell. After having two electrons it matches with the valence shell electron configuration of Helium (1s2), nearest noble gas of hydrogen.
N2H4 Lewis Structure Lone Pairs
Lone pairs are those valence electrons which are shown around the respective atoms as electron dots in lewis structure and does not participate in bond formation.
- Nonbonded electron = Total number of valance electron – number of bonded electrons.
- Nonbonding electrons in each of the two nitrogen atoms = 5 – 3 = 2 or 1 pair of lone electron.
- Nonbonding electrons in each of the four hydrogen atoms = 1 – 1 = 0
Therefore, total number of nonbonding electrons = 2×2 = 4.
N2H4 Valence Electrons
Valence electrons reside in the outer most shell of any atom and involved in bond formation due to greater reactivity. Because the attraction of nucleus is least in the outer most shell.
N2H4 is made of two nitrogen and four hydrogen atoms. Nitrogen has electron configuration 1s2 2s2 2p3. The 2s and 2p electrons are regarded as valence shell electrons. Thus, the number of outer most shell electrons in nitrogen atom is 5. Hydrogen has one electron in 1s orbital (1s1) and it is its valence electrons.
Therefore, total number of valence electrons in hydrazine = (2×2) + (1×4) = 8
Is N2H4 an electrolyte?
Electrolytes which are containing ions are dissolved in water and dissociated into two oppositely charged ions in aqueous solution. Electrolytes are basically ionic compound.
N2H4 is not an electrolyte because it is a covalent compound. It cannot be dissociated into two oppositely charged ions.
Is N2H4 ionic or covalent?
The basic difference between ionic and covalent compound is that valence electrons are completely transferred from one atom to another atom in ionic compound and are shared between two atoms in covalent compound depending upon the electronegativity difference.
N2H4 is a covalent compound because the electronegativity difference between nitrogen and hydrogen is not so high and both are nonmetal atoms. Valence shell electrons of each of the constituent atoms (two nitrogen and four hydrogen) are shared between them, not completely transferred from the valence shell of one atom having lesser electronegativity to the valence shell of another atom with greater electronegativity like any other ionic compound.
Bonding electrons are shifted towards the nitrogen due to having greater electronegativity with comparing to hydrogen.
Therefore, N2H4 is a covalent compound with six sigma covalent bonds.
Is N2H4 polar or nonpolar?
Presence of dipole moment makes a molecule polar and a molecule with zero dipole moment is considered as nonpolar. Polarity depends upon the electronegativity difference between the atoms involved in a bond formation and the orientation of the polar bonds. Though a molecule contains polar bonds but sometimes it can be nonpolar due to mutual cancellation of the direction of the polar bonds.
N2H4 is a polar molecule (µ= 1.85 D) as there is a difference of electronegativity between nitrogen and hydrogen, which makes the N-H bonds polar. The structure of N2H4 is trigonal pyramidal. Thus, mutual cancellation of the polar N-H bonds cannot be happened.
Therefore, N2H4 is a polar molecule.
Is N2H4 an acid or base?
N2H4 is a strong base even stronger than NH3. It is a lewis base which can donate nonbonding electrons to the acid or any electron deficient atom or molecule. The two lone pairs of two nitrogen atoms make the hydrazine a strong base than ammonia having one nitrogen atom.
Aqueous solution of hydrazine (64 weight %) is highly alkaline in nature having pH = 12.75.
Is N2H4 a hydride?
N2H4 is basically a pnictogen hydride. Group-15 elements (N, P, As, Sb, Bi) are considered as pnictogen molecules. It is not a metal hydride like NaH. But hydrazine is also a very good reducing agent like any metal hydrides.
Is hydrazine corrosive?
Hydrazine or N2H4 is highly toxic substance if it is used in solution (NH2NH2. xH2O). It can cause different complications in living body like skin and eye irritation, nausea, vomiting, breathing problem, headache, dizziness, depression lethargy and many more. Due to excessive use of hydrazone, organ damage like kidney, liver and central nervous system (CNS) can be happened.
Is hydrazine conjugate acid?
It is the conjugate base of hydrazinium ion (N2H5+). After elimination of one hydrogen atom from N2H5+, hydrazine is formed. Due to being a strong base, hydrazine can easily accept an H+ ion and form N2H5+. Thus, it is a conjugate base.
Does N2H4 dissolve in water?
Yes, N2H4 is a water-soluble liquid. It is also soluble in ethanol. N2H4 is a polar compound having a permanent dipole moment. Therefore, polar protic solvent can dissolve it.
Does N2H4 have hydrogen bonding?
Yes, N2H4 has hydrogen bonding. Hydrogen bonding can be two types-
- Intramolecular hydrogen bonding (H-bonding between the atoms of same molecule).
- Intermolecular hydrogen bonding (H-bonding between two molecules).
Hydrogen bonding is formed between a highly electronegative atoms and hydrogen atoms attached with an electronegative atom or polar group.
In N2H4, nitrogen is an electronegative atom and it participates in intermolecular hydrogen bonding (nitrogen from one hydrazine molecule with the hydrogen of another hydrazine molecule) with hydrogen atom.
Is N2H4 stable?
No, hydrazine is an unstable compound. It has two nitrogen atoms having two lone pairs which are facing repulsion from each other. Because nitrogen is a small atom and repulsion is greater in case of nitrogen with respect to other atoms of group-15 atoms. Thus, the N-N bond in N2H4 becomes weak and make hydrazine an unstable compound.
Conclusion
N2H4 is a trigonal pyramidal compound with a bond angle less than 109.50. It is dissolved in water due to its polar nature and being a covalent compound. Excessive use of hydrazine can cause hazards to living body due to its high toxicity.
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I am Aditi Ray, a chemistry SME on this platform. I have completed graduation in Chemistry from the University of Calcutta and post graduation from Techno India University with a specialization in Inorganic Chemistry. I am very happy to be a part of the Lambdageeks family and I would like to explain the subject in a simplistic way.
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