CuO Lewis Structure & Characteristics (13 Complete Facts)

CuO or copper oxide is the borderline element oxide having a molecular weight of 79.54 g/mol. We will learn about CuO in detail.

In the CuO, Cu shows a +2 oxidation state and for this reason here Cu has a d9 system. It is a transition metal atom and CuO is the transition metal oxide, which is basic in nature when it reacts with water from the base. Due to the d9 system, it shows tetragonal elongation.

Due to Jahn Teller distortion, the geometry around Cu(II) center changes from octahedral to tetrahedral. It can also be reduced the Cu metal in presence of hydrogen. Now we will discuss the hybridization, lewis structure, bond angle, and shape with proper explanation in the following part of the article.

1.      How to draw the CuO lewis structure

With the help of the octet rule, valency, molecular orientation, and central atom we can draw the lewis structure in many steps. Let us draw the lewis structure of CuO.

Counting the total valence electrons

We have to count the total valence electrons for the CuO by counting the individual valence electrons for Cu and O. the total valence electrons for the copper oxide are 15, where 9 3d electrons of copper are involved as because Cu is here +2 oxidation state.

Choosing the central atom

For the lewis structure construction, we need a central atom because all the atoms are connected by a suitable number of bonds with that particular atom. Based on the size and electropositivity we have to select the central atom. keeping all consideration, Cu is chosen as the central atom here.

Satisfying the octet

Every atom whether it belongs to the d or p block needs to be filled with its valence orbital by accepting a suitable number of electrons for the successive bond formation. To complete the octet Cu needs 10 and O needs 8 electrons as they belong to the d and p block respectively.

Satisfying the valency

During the octet formation, each atom should be aware that they can form that number of stable bonds which is their stable valency. As per octet electrons required 10+8 = 18 for the CuO formation, but the valence electrons are 15, so the remaining electrons should be filled by the stable valency of each atom.

Assign the lone pairs

After octet and bond formation, if electrons are left in the valence shell of each respective atom, then those electrons exist as lone pairs over that particular atom in a molecule. In CuO, only O contains 2 pairs of lone pairs because it has 4 excess electrons after the bond formation in its valence shell.

2.      CuO valence electrons

Electrons are present in the valence shell of each atom and are responsible for its chemical property and are called valence electrons. Let us count the valence electrons of CuO.

The total number of valence electrons for the CuO molecule is 15. There are 9 3d electrons from the Cu site and 6 electrons from the O site, so we just count the individual atoms’ valence electrons and just added them together to get the total valence electrons for the CuO molecule.  

  • The valence electrons for the Cu is 9 (Cu2+ – 3d9)
  • The valence electrons for the O are 6 ([He]2s22p4)
  • So, the total number of valence electrons for CuO is 9+6 = 15 electrons.

3.      CuO lewis structure lone pairs

The electrons that exist in the [paired form in the valence shell after the bond formation in excess are called lone pairs. Let us predict the lone pairs over CuO.

There are only 2 pairs of lone pairs present which means 4 electrons are present in the valence shell which has no contribution to the bond. Those electrons form the O site because O has six valence electrons; among them, only two electrons are involved with Cu2+ in bond formation.

  • We can predict the lone pairs over each atom by using the formula, lone pairs = electrons present in the valence orbital – electrons involved in the bond formation
  • So, the lone pairs are present over the Cu atom, 2-1 = 1
  • The lone pairs present over the O atom, 6-2 = 4
  • An unpaired electron cannot be a lone pair, so Cu has zero lone pairs and O has 2 lone pairs or 4 electrons.

4.      CuO lewis structure octet rule

To complete the valence orbital of each atom every atom accepts a suitable number of electrons is called the octet rule. Let us see the octet of the CuO molecule.

CuO follows the octet rule because both Cu and O are not completed their valence orbital yet. So, they try to complete their valence electrons through bond formation. O needs two more electrons to complete the octet, as because it belongs to the p block element so it needs 8 electrons in its valence orbital.

Cu is a transition metal element, so it completed its octet to full fill the d orbital by the electrons, but here Cu exists as Cu(II), so it has already 9 electrons in its valence shell, it requires only one electron to complete the valence orbital and follow the octet rule.

5.      CuO lewis structure shape

The molecular shape is the proper arrangement of the elements by substituent atoms to gain a perfect geometric structure. Let us predict the shape of CuO.

CuO is linear in shape, where Cu is attached to O by a double bond. So, there is no chance of deviation of the bonding shape which can be confirmed from the following table.

No. of
bond pairs
No. of
lone pairs
Shape   Geometry    
AX 1 0 Linear   Linear
AX2         2 0 Linear   Linear  
AXE        1 1 Linear   Linear  
AX3 3 0 Trigonal
AX2E      2 1 Bent Trigonal
AXE2      1 2 Linear   Trigonal
AX4 4 0 Tetrahedral Tetrahedral
AX3E      3 1 Trigonal
AX2E2                  2 Bent Tetrahedral
AXE3                      1 3 Linear   Tetrahedral
AX5 5 0 trigonal
AX4E      4 1 seesaw trigonal
AX3E2     3 2 t-shaped          trigonal
AX2E3     2 3 linear    trigonal
AX6 6 0 octahedral octahedral
AX5E      5 1              square
AX4E2                     4 2 square
Screenshot 2022 09 26 194038
CuO Molecular Shape

The geometry or shape of a molecule is predicted by the VSEPR (Valence Shell Electrons Pair Repulsion) theory, and the theory stated that if a molecule has type AX and there are no lone pairs over the central atom then they should be linear in shape and no change in geometry occurs.

6.      CuO lewis structure angle

Bond angle made by the central and substituent atoms for proper orientation in particular geometry. Let us calculate the bond angle of CuO.

The bond angle between Cu and O in CuO is 1800 because the linear geometry bond angle always is 1800. There are no lone pairs – bond pairs repulsion occurs so no need to change the bond angle. Two atoms always make the bond angle at 1800 as they always adopted a linear shape or straight line.

Screenshot 2022 09 26 194047
CuO Bond Angle
  • The bond angle value can be calculated by the hybridization value.
  • The bond angle formula according to Bent’s rule is COSθ = s/(s-1).
  • Here the central atom Cu is pd hybridized, so the p character is 1/2th
  • So, the bond angle is, COSθ = {(1/2)} / {(1/2)-1} =-( 1)
  • Θ = COS-1(-1) = 1800
  • So, from the hybridization value, the bond angle for calculated and theoretical value is the same.

7.      CuO lewis structure formal charge

The formal charge is a hypothetical concept, where the electronegativity of all atoms is equal and can predict the charge of the atom. let us calculate the formal charge of CuO.

The net formal charge of the CuO is zero because the ion Cu2+ is neutralized by the charge of the oxide ion. Because those charges equal but opposite in sign. In the copper oxide, both Cu and O can break into di ion form and we have to calculate the individual charge.

  • The formal charge of the NaH2PO4 can be calculated by the formula, F.C. = Nv – Nl.p. -1/2 Nb.p
  • The formal charge possesses by the Cu2+ is, 4-0-(4/2) = +2
  • The formal charge possesses by the O2- are, 6-4-(8/2) = -2
  • So, Cu2+ and O2- showing di ionic form and the magnitude of the charge is the same but due to opposite in nature they cancel out each other and accounting the neutral form of the CuO.

8.      CuO hybridization

 Due to the different energy of the orbitals central atom undergoes hybridization to form a hybrid orbital of equivalent energy. Let us predict the hybridization of CuO.

The central Cu is pd hybridized to form a covalent bond in the CuO molecule which can be discussed below.

Structure    Hybridization
State of
of central atom
Bond angle
1.Linear          2          sp /sd / pd 1800
3 sp2                    1200
3.Tetrahedral  4 sd3/ sp3 109.50
5 sp3d/dsp3 900 (axial),
5.Octahedral    6         sp3d2/ d2sp3 900
7 sp3d3/d3sp3 900,720
Hybridization Table
  • We can calculate the hybridization by the convention formula, H = 0.5(V+M-C+A),
  • So, the hybridization of central Cu is, ½(2+2+0+0) = 2 (pd)
  • One p orbital and one d orbitals of Cu are involved in the hybridization.
  • The π bond between Cu and O is not involved in the hybridization.

9.      CuO solubility

The solubility of the molecule depends on the tends of dissociation into ions and gets soluble in that solvent. Let us see whether CuO is soluble in water is not.

CuO is insoluble in water because the ionic interaction between Cu and O is very strong as there is a double bond present. So, the bond enthalpy of CuO is stronger than hydration energy, so water molecules can break the bond between CuO molecules, and also Cu2+ is insoluble due to its soft nature.

List of some solvents where CuO is soluble

  • Ammonium chloride
  • Potassium cyanide
  • Ammonium carbonate ( Partial soluble)

10. Is CuO solid or liquid?

A molecule’s physical state depends on the bonding nature and applied temperature and pressure. Let us see whether CuO is solid or not.

CuO is a solid black power because there is more lattice energy present with the copper oxide molecule. In the crystal form, it adopted a monoclinic structure where two unit cell is present and the lattice is very strong at room temperature due to ionic bonding, so CuO exists as solid at room temperature.

11. Is CuO polar or nonpolar?

The polarity of a molecule depends on the value of the resultant dipole-moment value and electronegativity difference. Let us see whether CuO is polar or not.

CuO is a polar molecule because there is a resultant dipole-moment present and due to the electronegativity difference, there are also flows of dipole-moment from the Cu to O observed. Due to linear structure, there is no way of canceling the dipole moment between Cu and O and for this reason, CuO is polar.

The liner shape is not asymmetrical but there is no other dipole moment that works in the CuO molecule which can be canceling the dipole moment.

12. Is CuO acidic or basic or salt?

The acidity of basicity nature of a molecule depends on the presence of acidic proton or hydroxide anion. Let us see whether CuO is acidic or not.

CuO is neither acidic nor base rather it is a basic oxide, because when it reacts with water to form a strong base of copper hydroxide. All the metal oxides are basic in nature so CuO is also basic, but itself does not participate in any acid-base reaction because it does not have any acidic proton.

According to the HARD SOFT ACID BASE principle, Cu2+ is a borderline acid that is neither strong nor weak, but oxide is hard-base in nature.

13. Is CuO electrolyte?

Electrolyte can be ionized in the solution when gets dissociated and carry electricity through the solution. Let us see whether CuO is an electrolyte or not.

CuO is an electrolyte in nature because when it dissociates in an aqueous solution then it forms Cu2+ and O2- and due to the formation of those charged particles it can carry electricity through the solution. The charge density of oxide ions is very high.

14. Is CuO ionic or covalent?

On the theory of polarizability by Fajan’s rule, we can predict if a molecule is ionic or covalent in nature. Let us check whether CuO is ionic or covalent in nature.

CuO is ionic in nature due to there being ionic interaction present between Cu and O atoms. Also, due to the polarizability rule, Cu2+ can be polarized in the anion oxide and form an ionic bond, and due to the electronegativity difference between Cu and O, the bond is more polar like an ionic molecule.

The bond is formed between Cu and O by the total donation of electrons.


CuO is the basic oxide of a borderline transition element. Cu is in a +2 oxidation state so it can be oxidized and behaved as a reducing agent.

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