NH2– is the formula of azanide or amide anion. Let us explore some important facts about it.
In the Lewis structure of NH2–, central atom is Nitrogen. It is surrounded by two Hydrogen atoms. Nitrogen atom forms covalent bond with the Hydrogen atoms. There are 2 non-bonded pairs on the central atom.
Let us explore NH2– Lewis structure and its characteristics below.
How to draw NH2– Lewis structure?
The Lewis structure is an electron dot diagram. Let us learn to draw it for NH2–.
Step 1: Finding the valence electrons
Nitrogen belongs to group 15 so it has 5 valence electrons. Hydrogen belongs to group 1 so it has 1 valence electron. One additional electron that is giving the negative charge on NH2–. Thus, total valence electrons in NH2– ion = 5 + 2*1 + 1 = 8 electrons
Step 2: Select the central atom
The least electronegative forms the central atom in the Lewis structure Hydrogen is less electronegative than nitrogen but it cannot form more than one bond and it has only one electron. Thus, Nitrogen forms the central atom in NH2–.
Step 3: Complete the duplet of outer hydrogen atoms
Hydrogen, being exception to octet rule tries to achieve the noble configuration like Helium. Out of 8, four electrons are used in forming 2 single bonds between N and H. Keep the remaining 4 electrons on Nitrogen. Thus, Nitrogen has two lone pairs.
Step 4: Check the Formal charge
Formal charge on central Nitrogen atom is -1 and 0 on each hydrogen atom. Thus, net charge on NH2– is -1.
NH2– Lewis structure shape
We can decide the shape of a molecule using VSEPR theory. Let us discuss it.
NH2– anion has bent molecular shape and tetrahedral electron geometry. The VSEPR notation for NH2– is AX2E2, where A is the central atom, X represent the atoms bonded to central atom, E represent the non-bonded pair on the central atom. This notation corresponds to bent molecular shape.
NH2– Lewis structure formal charge
Formal charge helps us to choose the best Lewis structure for a molecule. Let us discuss it.
The net formal charge on NH2 is -1. Formal charge is the charge which is obtained when we subtract bonding and non-bonding electrons from the valence electrons of a molecule. The formula to calculate the formal charge is, Formal Charge = valence electrons – ½ *(bonding electrons) – non-bonding electrons.
The formal charge on nitrogen and each of the two hydrogen atoms in Lewis structure ofNH2– is as follows–
- On each Hydrogen = 1 – 0.5*2 – 0 = 0
- On the central Nitrogen atom = 5 – 0.5*4 – 4 = -1
- Net formal charge on NH2 = -1.
NH2– Lewis structure angle
The bond angle in the molecule is affected by the repulsion between the lone pairs, lone pair-bond pair and bond pair-bond pair present on the central atom. Let us discuss.
The bond angle of NH2– is 104.5 degrees. The bond angle is less than the normal 109.5 degrees because of repulsion between the two lone pairs present on the central Nitrogen atom.
NH2– structure octet rule
Octet rule is the rule which tells about the preference of the atoms to have eight electrons in their last shell. Let us explore it.
In the NH2–, Hydrogen completes its duplet as it is an exception to octet rule. Hydrogen has achieved noble gas configuration of Helium. Nitrogen has eight electrons surrounding it. Thus, Nitrogen has gain octet of electrons.
NH2– Lewis structure lone pairs
Lone pairs are the unshared electron pairs. They are present in the outermost shell of an atom. Let us discuss it.
There are 2 lone pairs in NH2–. The central atom N has 2 lone pairs on it. The outer Hydrogen atoms have 0 lone pairs. The formula to calculate lone pairs is, lone pairs = ½*(Valence electrons of central atom – Number of bonded atoms to central atom)
NH2– valence electrons
The valence electrons are the electrons occupying the outermost shell of an atom. Let us discuss it.
Valence electrons in NH2– anion is 8. There are two lone pairs on central Nitrogen atom and it is bonded to two Hydrogen atoms by single bond.
The electrons in NH2–is as follows-
- Two lone pairs on Nitrogen = 4 electrons
- Two single bonds between N and H = 4 electrons
- Thus, total valence electrons in NH2– = 8 electrons
Hybridization is the process necessary for the central atom to form equivalent orbitals for bond formation. Let us discuss it.
The central atom Nitrogen in NH2– undergoes sp3 hybridization. The formula to find out Hybridization is, Hybridization = ½*(valence electrons + monovalent atoms – cationic charge + anionic charge)
- Number of valence electrons in N = 5
- Number of monoatomic atoms attached to N = 2
- Cationic charge = 0
- Anionic charge = 1
- Thus, Hybridization = ½*(5 + 2 – 0 + 1) = 4 (sp3).
Solubility is the maximum amount of substance that is soluble in the given solvent. Let us explore it.
NH2– is a polar molecule so it can form hydrogen bonds with water and C2H5OH and so is soluble in them. It is soluble in the following solvents –
Is NH2– polar or non-polar?
Polar molecules have bonds with partial positive and negative ends while non-polar molecules do not. Let us find out for NH2–.
NH2– is a polar anion because N and H has a electronegativity difference of 0.84. Thus, the partial charges develop at both the ends. This produces a net dipole moment in the anion.
Is NH2– acidic or basic?
Bronsted-Lowry acid is one which gives a H+ while Bronsted-Lowry base is one which takes it. Let us discuss it.
NH2– is a Bronsted-Lowry base as it can take a H+ from a Bronsted-Lowry acid to form ammonia, NH2– + H+ = NH3. Thus, NH2– is a strong base.
Is NH2– electrolyte?
Electrolytes can conduct electricity through ions. Let us find out whether NH2–is an electrolyte or not.
NH2– anions shows a fast ion conductivity. NH2– can conduct electricity. Thus, NH2– is an electrolyte.
Is NH2– ionic or covalent?
Covalent compounds consist of bond between non-metals while an ionic compound consist of bond between a metal and a non-metal. Let us understand it.
NH2– is a covalent compound because both Nitrogen and Hydrogen are non-metals and there is sharing of electrons in the bond formed between N and H.
In short, NH2– ion has 8 valence electrons. The central atom Nitrogen is sp3 hybridized. The molecular shape of NH2– is bent and electronic shape is tetrahedral. It is a polar in nature.