Chemistry » Ionic And Covalent Bonding

Chemical bonding of ionic and covalent bonds

Previous Topic : Chemical Laws And Its Calculations

periodic-table-for-first-20-elements

The table above is called the periodic table

Note : Today’s topic is based on chemical combination and bonding not periodic table.

In the table above, all other elements except group 8 elements try to attain the structure of a stable octet or duplet electrons (rules), although we are discussing about chemical bonding of ionic and covalent bonds today.

Brief : Group 8 (rare or noble gases) are chemical unreacted because they already have 8 electrons in their outermost shell and chemical reaction is based on the concept of electron sharing. I’ll explain better when we get to periodic table.

Atoms of an element combine with one another in various ways and this combination are called bonding.

Chemical bonding of ionic and covalent bonds

There are many different types of bonding of which covalent bonding, electrovalent or ionic bonding, co-ordinate covalency or co-ionic bonding, hydrogen bonding, metallic bonding and van der waal’s force.

Let analyze covalent and ionic bonding today and probably other bondings next class.

Straight to business.

Ionic Or Electrovalent Bonding

Ionic or electrovalent bonding is the type of chemical bonding between metal and non-metal and the most important principle in ionic bond is that, it’s a donor-acceptor principle in which there is a complete electron transfer and the atoms formed are usually present as ions.

During ionic bonding, the donor atom is usually a metal of relatively big size and the acceptor atom is usually a non-metal and relatively small size.

During the bonding, an atom of a metallic element or group loses electrons from its outermost shells.
The number of electrons is equal to number of its valency to attain a stable configuration and then becomes positively charged ion which is known as cations.

I believed I have explained how to write a chemical configuration for elements and also discussed about auf bau principle during our class session on Atoms And Molecules

Let look at the formation of sodium chloride as ionic bonding example

Sodium (Na) and Chlorine (Cl)

Na — e- → Na+

The non-metallic atom gain the electron lost by the metallic atom and become negatively charged, this negatively charged ion is called acceptor or anions.

Cl + e- → Cl-
Hence,

Na+ + Cl- → NaCl
formation-of-nacl-in-ionic-bonding

The sodium chloride compound formed crystallizes as a face-cented cube. In the end face of the cube, Na+ ion is found to occupy the center, and the four corners of the face are also occupied by Na+ ions with four Cl- ions spaced equally between them.

During the process, the only movement or motion is vibration.
When the two atoms I.e Na & Cl bonded, the solid appears to be rigid and has a negligible electrical conductivity.

Note : The attraction between sodium ion and chloride ion is electrostatic attraction (please note this)

Another example of electrovalent or ionic bonding is calcium chloride.

Before combination (bonding), calcium has 20 proton(atomic mass) I.e 20 electrons with electronic configuration of 2,8,8,2.

And chlorine has 17 proton (atomic mass) I.e 17 electrons with electronic configuration of 2,8,7.

Calcium (Ca) has 2 electrons in its outermost shell and chlorine has 7 electrons in its outermost shell.

That means, Calcium is looking for 6 electrons and chlorine is looking for one electron to obey octet rule.

In order for bonding to take place, the two valency of calcium will be transferred to chlorine atoms so that chlorine can also obey octet rule.
When this happens, the two elements becomes bonded together.

Other examples of ionic bonding is calcium oxide (CaO), Potassium chloride (KCl), just have it in mind that ionic bonding occurs between metal and non-metal and make sure you note the special note below

Please Note

Like I said above, ionic or electrovalent bonding occurs in metals and non-metals, but not in Aluminium Chloride (AlCl3), the bond between Aluminium chloride is covalent bonding not ionic or electrovalent bonding. Yes aluminum is a metal and chlorine is a non-metal, but have you also forget that aluminum is an element of semiconductor, that is under physics, let just agree in chemistry that aluminium is a semi-metal. You will know more on types of elements and groups when get to periodic table.
But please note what is above, the bond between Aluminium and Chlorine to form Aluminium Chloride (AlCl3) is covalent bond not ionic bond

They also ask this question that, what is the bond between semiconductors
Use that one to crack your brain, send me a private message with your answer and explanation.
Please don’t ask other candidates in your group or forum, think first !!!, and also, whenever you are ask to answer a question, don’t just open your browser tab and start Google searching, first go through your textbooks and lesson note. Please, it’s for your own good. It’s like the same reason your english teacher always tells you not to refer to dictionary as your first thought to finding the meaning of words but instead use the environment.

For new candidates that doesn’t know, what I meant by send me a private message and to not ask others, just register and you will be able to add other candidates as a friends including the tutors, it’s really fun, try it out and see.

So where are we?
Yeah characteristics of ionic bonding.

Characteristics Or Properties Of Electrovalent Or Ionic Compound (Bonding)

a] Ionic or electrovalent compounds form ions in water, meaning they do not contain molecules

b] Since they dissolve or dissociate in water to form ions, hence, they conduct electricity.

c] Ionic or electrovalent compounds have high melting and high boiling point.

d] Ionic compounds occur mainly in inorganic compounds.
Hence, they do not dissolve in organic solvents such as benzene, phenymetane, ether, toluene, etc.

Do you know what ether is? I can’t wait for us to get to organic chemistry. But have it in mind that esther is different from ether.

Let go to covalent bond.

Covalent Bond

Covalent bonding are bonding between relatively small size elements, with the main principle of sharing electrons between atoms such that each of the atoms in the molecules has the electron arrangement of noble gases.

The two main atoms (elements) involved in covalent bonding are always small.
For example Chlorine (Cl)
When two atoms of chlorine combine together to form chlorine gas (Cl2), both chlorine are relatively small in size with electronic configuration of 2, 8, 7.

Note : In covalent bonding, the atoms contribute one electron each to a shared-pair and molecules are produced not ions.

chlorine-gas-formation-in-covalent-bonding

During covalent bonding, the electron clouds overlap. the two clouds containing one electron each overlap to form a single cloud between the atoms.

Other examples are: hydrogen gas (H2), Water (H2O), Ammonia (NH3), Methane (CH4), etc.

Should we look at their structure? Yes, we should.

Hydrogen Gas Structure

Hydrogen gas (H2) is a diatomic compound. That is, hydrogen gas contains 2 atoms.

There is a single covalent bond between the atoms.
Below is the formation of hydrogen gas.

hydrogen-gas-formation-in-covalent-bonding

Methane Structure

formation-of-methane-molecule-in-covalent-bonding

From the above image, the shared electrons are displayed towards the carbon, there are no lone pairs and the molecule is tetrahedral in shape.

Brief :

Shape Of Molecules

a] Methane (CH4) is tetrahedral in shape

b] Water (H2O) is bent ( letter V) in shape.

c] Carbon (iv) oxide (CO2) is linear (straight) in shape.

d] Ammonia (NH3) is asymmetric in shape.

Structure Of Water

1] Water (H2O) has eight protons in the nucleus compared with one in the hydrogen nucleus

2] Water has two lone pairs of electrons. I believed I have explain what a lone pair is during our class session on atoms and molecules.

3] Water molecules are bent in shape.

formation-of-water-molecule-in-covalent-bonding

Structure Of Ammonia

1] Nitrogen has seven protons in the nucleus compared with one in the hydrogen nucleus.

2] Nitrogen has one lone pair of electrons.

3] Ammonia molecule is asymmetric in shape.

formation-of-ammonia-molecule-in-covalent-bonding

Characteristics Or Properties Of Covalent Compounds (Bonding)

a] Covalent compounds molecules does not form ions in solution, I.e they do not dissociate in water to form ions.

b] Because of the characteristic above, covalent compounds do not conduct electricity, hence. They are non-electrolyte.

Brief : meaning that, all compounds, substances or elements that dissociate in water to form ions conduct electricity.

c] Covalent bonding occur mainly in organic compounds, meaning that, they are soluble in organic solvents for example, benzene can dissolves in camphor and carbon disulphide can dissolves in sulphur

d] Covalent compounds has low melting and boiling point.

Differences Between Ionic And Covalent Bond

a] Ionic bonding is based on the principle of transferring of electrons while Covalent bonding is based on the principle of sharing of electrons.

b] Ionic bonding occur mainly between relatively big size and small size elements while Covalent bonding occur mainly between relatively small size elements.

c] Ionic bonding occur between metal and non-metal except in aluminium chloride [AlCl3] while Covalent bonding occur between non-metal and non-metal.

d] Ionic bonding compounds are inorganic, I.e the cannot dissolve in organic solvents such as benzene while Covalent bonding compounds are organic, I.e the can dissolve in organic solvents such as benzene.

e] Ionic bonding compounds dissolves or dissociate in water to form ions, I.e they conduct electricity when dissolves in water (that why they are used as an electrolyte) while Covalent bonding compounds does not dissolves or dissociate in water to form ions but to form molecules, I.e they can or do not conduct electricity when dissolves in water (that is why they are used as non-electrolyte).

f] Ionic bonding compounds have high melting and boiling points while Covalent bonding compounds have low melting and boiling points.

That all on chemical bonding of ionic and covalent bonds.

Next Topic : Co-ordinate Or Co-ionic And Metallic Bonding

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