CaSO4 Lewis Structure & Characteristics: 15 Complete Facts


Valence electron of a compound represented in the schematic form of lines and dots are called lewis structures. Let us discuss brief details on the CaSO4 lewis structure.

CaSO4 lewis structure consists of main three elements, calcium, sulfur, and oxygen atoms. It has 1 Ca, 1 S, and 4 O atoms in its molecule. This is an ionic compound as it is composed of metal and non – metal moieties. It has an ionic bond between Ca2+ metallic ion and the SO42- non – metallic ion.

CaSO4 is the chemical formula of calcium sulfate. The S and O atoms are joined with covalent bonds in SO42- of CaSO4 lewis structure. Let us have some more discussion on a formal charge, the octet rule, lone pair, valence electrons, and characteristics of CaSO4 lewis structure and some more facts about it.

How to draw CaSO4 lewis structure?

The steps and rules to draw the CaSO4 lewis structure are described in the below steps.

Valence electrons and bonding of CaSO4:

Calculate all the valence electrons available on the CaSO4 lewis structure by summation of all valence electrons of each Ca, S, and O atom. Make bonding within all the atoms present in it. Sulfate ion has covalent bonds within S and O atoms. The Ca ion is attached with an ionic bond with the SO4 ion.

Lone pair electrons and octet rule on CaSO4:

As the bonding is done between all atoms of CaSO4, the remaining valence electrons get put first on outer bonded atoms and then on central atoms. The octet rule should apply to each atom of CaSO4 to find whether they have complete or incomplete octets.

The formal charge and shape of CaSO4:

The formal charge of the CaSO4 lewis structure should be calculated with the help of using the given formula. Later, identify its shape and geometry with hybridization and bond angles.

CaSO4 lewis structure

CaSO4 valence electrons

The electrons present on the outermost orbital of an atom are known as valence electrons. Let us have a brief discussion on CaSO4 lewis structure valence electrons.

CaSO4 lewis structure has 32 valence electrons. The Ca atom is in the 2nd group in periodic table and has 2 valence electrons. The S and O atoms belongs to 16th group in periodic table and have 6 valence electrons. It has exchange of electrons with Ca and SO4 so add and reduce electrons from both.

Below is the given calculative explanation for CaSO4 lewis structure valence electrons.

  • Calcium metal has valence electrons is = 2 x 1 (Ca) = 2
  • 2+ charge on Ca atom so minus 2 electrons on it = 2 – 2 = 0
  • Sulphur atom has valence electrons is = 6 x 1 (S) = 6
  • Oxygen atom has valence electrons is = 6 x 4 (O) = 24
  • -2 charge on SO4 ion so add 2 electrons on it = 2
  • Total valence electrons on CaSO4 lewis structure is = 0 (Ca) + 6 (S) + 24 (O) + 2 = 32
  • Total electron pairs on CaSO4 is identified by dividing its valence electrons by 2 = 32 / 2 = 16
  • Thus, the valence electrons on the CaSO4 lewis structure are 32 and have 16 electron pairs.

CaSO4 lewis structure lone pairs

Extra unshared electrons present on any atom or molecule are called the lone pair of electrons. Here we are discussing the CaSO4 lewis structure lone pair electrons.

CaSO4 lewis structure has total of 12 lone pair electrons. Ca2+ has zero electrons due to the loss of electrons and does not possess any lone pair electrons. The SO42- ion gains 2 electrons from the Ca atom and has 32 electrons. 8 electrons are being bond pairs as they form bonds within S and O atoms.

It has 4 S – O bonds and 24 remaining valence electrons get placed on outer bonded 4 O atoms. Each O atom gets 6 unshared electrons. Thus, it has 3 lone pair electrons on each O atom of SO42-. Hence, CaSO4 has 12 lone pair electrons only present on O atoms of SO42-.

CaSO4 lewis structure octet rule

The atoms having 8 electrons in their outer orbit is considered stable in nature as described in the octet rule. Let us apply the octet rule to the CaSO4 lewis structure.

CaSO4 lewis structure has complete octets of all S and O atoms in SO42- ion. Ca2+ ion has an empty last orbital due loss of its 2 valence electrons. The central S atom of SO42- ion has a complete octet as it is surrounded by 8 bonding electrons.

The outer 4 O atoms of SO42- ion has complete octets as they are surrounded by 2 bonding electrons and 6 unshared electrons. Thus all 4 O atoms contain total of 8 surrounding electrons and have a complete octet.

CaSO4 lewis structure formal charge

The molecules or atom that contains a positive or negative charge it is called a formal charge. Below is the detailed description of the CaSO4 lewis structure formal charge.

The formal charge of CaSO4 Lewis structure is = (valence electrons – non-bonding electrons – ½ bonding electrons)

The CaSO4 lewis structure formal charge calculation is explained below – given table.

Atoms of CaSO4
lewis structure
Valence electrons on
Ca, S, and O atom
Non – bonding electrons
on Ca, S, and O atom
Bonding electrons on
Ca, S, and O atom
The formal charge on
Ca, S, and O atom
Calcium (Ca) atom020000( 2 – 0 – 0 / 2 ) = + 2
Sulfur (S) atom060008( 6 – 0 – 8 / 2 ) = + 2
Oxygen (O) atom060602( 6 – 6 – 2 / 2 ) = – 1
CaSO4 lewis structure formal charge, Ca = + 2, S = + 2, O = – 1

CaSO4 lewis structure shape

The atomic arrangement in any molecule as per its geometry and bonds is known as its molecular shape. Take look at the detailed explanation of the CaSO4 molecular shape.

The CaSO4 lewis structure has the tetrahedral shape of its SO42- ion. Ca2+ cation is a separate species that is attached to SO42- anion by an ionic bond. The tetrahedral shape of CaSO4 is only due to the SO42- ion. In accordance with VSEPR theory, it follows the AX4 generic formula.

The central S atom of SO42- ion is attached with bonded 4 O atoms which are at the corners of a regular tetrahedron and forms a tetrahedral geometry.

CaSO4 hybridization

The overlapping of 2 different atomic orbitals of the same element and forming a new hybrid orbital with the same energy is hybridization. Let us discuss CaSO4 hybridization.

The CaSO4 lewis structure has ‘sp3’ hybridization of the central S atom. The sulfur atom contains steric number 4. The steric number of S atom is determined as = number of bonds on S atom + lone pairs on S atom. Thus, S atom has steric number = 4 + 0 = 4.

According to VSEPR theory atoms with 4 steric number has sp3 hybridization and tetrahedral geometry. In the CaSO4 lewis structure, it has the overlapping of one ‘s’ and three ‘p’ orbitals of the central S atom. This forms a new hybrid ‘sp3’ hybrid orbital with equivalent energy as before orbitals.

CaSO4 lewis structure angle

The bond angle is the angle present between the two immediate bonds in a molecule. Let us have a brief discussion on the explanation of the CaSO4 bond angle.

The CaSO4 lewis structure has a bond angle of 109.5 degrees. There is a central S atom of the CaSO4 compound linked with four oxygen atoms in a tetrahedral manner. Thus as per the VSEPR module, it has an AX4 generic formula. Thus it has a 109.5 degrees O – S – O bond angle of CaSO4.

Is CaSO4 solid?

The atomic arrangement of a molecule in a definite geometry with closed packing of atoms is called solid compounds. Below we are discussing whether CaSO4 is solid or not.

CaSO4 is a solid compound. It is a colorless or white in color crystalline solid compound. It has various forms like anhydrite CaSO4, dihydrate CaSO4, or gypsum with various crystalline structures and colors like red, black, blue, etc. The Ca2+ and SO42- are tightly packed in their crystal structure.

Why CaSO4 is solid?

CaSO4 is a solid and crystalline compound because it can form an orthorhombic crystal structure. Both Ca2+ and SO42- ions are arranged in a closed packing of alternate layers in an orthorhombic cage. Each Ca2+ cation has 8 co-ordinations and is surrounded by 8 tetrahedral SO42- anions.

Each O atom of tetrahedral SO42- ion is surrounded by 3 Ca2+ cations. Thus, each O atom has 3 co-ordinations. Hence each Ca2+ cation and SO42- anion forms layers in an orthorhombic unit cell. So, this confirms its crystalline solid structure.

Is CaSO4 soluble in water?

The ability of a solute to dissociate in water and form hydrogen bonds in water shows its solubility in it. Take a look at the brief of CaSO4 solubility in water.

CaSO4 is soluble in water but it is slightly or sparingly soluble in water. CaSO4 on added to water reacts with water and get ionizes in it as Ca2+ and SO42- ions. CaSO4 does not completely ionize in the water and thus it is sparingly soluble in water. So, it forms a complex with water CaSO4.(H2O)2.

CaSO4 + 2 H2O → CaSO4.(H2O)2

Why CaSO4 is sparingly soluble in water?

CaSO4 is sparingly soluble in water because the hydration energy of CaSO4 is less than its lattice energy. The Ca2+ cations are tightly held with the SO42- anions. Thus it is dissolved in water a very less amount.  About 2 gm CaSO4 can soluble in water and after this limit, it gets saturated in water.

Is CaSO4 polar or nonpolar?

The development of dipoles and partial charges on the atoms of a molecule shows the polarity of that molecule. Let us discuss whether CaSO4 is polar or non-polar.

The CaSO4 compound is a polar species. It is an ionic molecule and contains a polyatomic non-polar anion SO42-. These SO42- of CaSO4 is basically a non – polar moiety. The non-polar SO42- is attached with Ca2+ cation making the CaSO4 polar in nature.

Why CaSO4 is polar?

The CaSO4 is a polar compound because of the presence of non-polar SO42- ions. The negative SO42- anion is attached with positive Ca2+ cation. It has an unequal distribution of electrons on both ions. So, dipoles get develops on both the ions due to the partial positive and negative charge on it.

Is CaSO4 a molecular compound?

Molecular compounds contain covalent bonding within their atoms and show the presence of various molecules in their structure. Let us see whether CaSO4 is molecular or not.

CaSO4 is not a molecular compound. It is an ionic compound. It has only an ionic bond within Ca2+ and SO42- ions and not a covalent bond. Covalent bonds are only on SO42-. All S and O atoms joined with covalent bonds still can’t show molecular nature. It has a charge on it and shows an ionic character.

Is CaSO4 acid or base?

The species which are H+ ion donors are acids and the species which are H+ ion acceptors are base. Take a brief look at the discussion of whether CaSO4 is acid or base.

CaSO4 is a non-acidic and non-basic compound. It is a neutral molecule.  The neutral compound is those which are the product of the acid-base reaction. CaSO4 compound is formed due to the reaction of a strong acid and strong base. Thus it confirms that it is a neutral compound.

Why CaSO4 is neutral?

CaSO4 is neutral because it has Ca2+ and SO42- ions which have +2 and -2 charges. Both these charges cancel out each other and are neutral compounds. CaSO4 is formed due to the reaction between sulphuric acid (H2SO4) and calcium hydroxide (Ca(OH)2). The reaction is given below.

H2SO4 (aq) + Ca(OH)2 (s) → CaSO4 (s) + 2 H2O (l)

Is CaSO4 electrolyte?

The compounds which get dissociate on adding to water and have the capacity to conduct electricity are called electrolytes. Let us discuss on CaSO4 electrolytic nature.

CaSO4 is an electrolyte. It is a weak electrolyte due to its low ionization in water. It has high lattice energy and low hydration energy. Thus it cannot completely ionize into the water due to the tight packing of the molecule. Also, it can conduct electricity and behave as an electrolyte.

Why CaSO4 is an electrolyte?

CaSO4 is an electrolyte because it is an ionic compound and formed due to a combination of metal and non-metal atoms. On adding CaSO4 to water it can dissociate into Ca2+ and SO42- ions. These ions can move freely into the water and conduct electricity on external electric field applications.

CaSO4 + H2O → Ca2++ SO42-

Is CaSO4 salt?

Acid and base compounds on reaction with each other produce salts which are neutral compounds. Here, we are discussing whether CaSO4 is a salt or not.

CaSO4 is a salt. It is the product of the neutralization reaction of a strong acid and a strong base which produce salts. When H2SO4 is reacted with Ca(OH)2 undergoes a neutralization reaction and produce a crystalline CaSO4 solid compound which is white in color or colorless. Thus, it acts as a salt.

Is CaSO4 ionic or covalent?

The ionic compounds formed due to electrostatic force of attraction, while covalent compounds due to strong sigma covalent bonds. Let us discuss on CaSO4 is ionic or covalent.

CaSO4 is an ionic compound. It is formed by combining metal and non – metal elements. It also contains two oppositely charged ions means cation and anion. There is an exchange of electrons between Ca and SO4 molecules due to which the positive and negative charge generated makes it ionic in nature.

Why CaSO4 is ionic?

CaSO4 is an ionic molecule because the Ca2+ cation and SO42- anion are strongly held together due to the strong electrostatic force of attraction and making a strong ionic bond between them. It also gets ionized into Ca2+ and SO42ions on adding to water which confirms its ionic character.

Conclusion:

CaSO4 lewis structure has 32 valence electrons and 12 lone pairs. It has complete octets of both S and O atoms of SO42 ion. It has a formal charge of +2 on Ca, +2 on S, and -1 on all 4 O atoms. It has a tetrahedral shape and an orthorhombic crystal structure. It has sp3 hybridization and 109.50 bond angle. It is polar ionic salt, electrolyte, and water-soluble.

Dr. Shruti Ramteke

Hello everyone I am Dr. Shruti M Ramteke, i did my Ph.D in chemistry. I have five years of teaching experience for 11-12 standard, B,Sc and MSc in chemistry subject. I have published total five research articles during Ph.D on my research work and i have fellowship from UGC for my Ph.D. My Masters with specilization Inorganic chemistry and my graduation with chemistry, zoology and environmental science subjects. thank You

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