CLASS :- 11
Topic :- ionic or electrovalent Bond
ionic or electrovalent Bond
ionic bond, also called electrovalent bond, type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound. Such a bond forms when the valence (outermost) electrons of one atom are transferred permanently to another atom. The atom that loses the electrons becomes a positively charged ion (cation), while the one that gains them becomes a negatively charged ion (anion).
Ionic bonding results in compounds known as ionic, or electrovalent, compounds, which are the best Example of formation of compounds between nonmetals Halogen family , chalcogen family and the alkali and alkaline-earth metals. In ionic crystalline solids of this kind, the electrostatic forces of attraction between opposite charges and repulsion between similar charges orient the ions in such a manner that every positive ion becomes surrounded by negative ions and vice versa. In short, the ions are so arranged that the positive and negative charges alternate and balance one another, the overall charge of the entire substance being zero. The magnitude of the electrostatic forces in ionic crystals is considerable. Accordingly, these substances tend to be hard and nonvolatile.
formation of sodium chloride
formation of magnesium chloride👇
formation of calcium fluoride👇
formation of magnesium oxide👇
formation of magnesium bromide👇
Formation of ionic bond :-
An ionic bond is formed by the complete transfer of one (Na , K) or more than one (Ca ,Mg) electrons from one atom to another atom as (F ,Cl , O , N). The atom losing one or more electrons becomes a cation( Na+, Mg++ Ca++ and Fe++)—a positively charged ion (F¯ , Cl¯ , O¯ ¯ and N ¯ ¯ ¯). The atom gaining one or more electron becomes an anion—a negatively charged ion
factor influence of the formation of ionic bond
1 :-lower ionization enthalpy :-Low ionization energy – elements with low ionization enthalpy have greater tendency to form an ionic bonds
2:-Higher electron gain enthalpy :-
Greater the value of Electron gain enthalpy (more negative) easier the formation of anion and more the probability of formation of ionic bond
3:-Higher lattice enthalpy
Low ionization energy – elements with low ionization enthalpy have greater tendency to form an ionic bonds
Example formation of sodium chloride
1:- Lattice enthalpy of ionic crystal :-wo main factors that contribute to the lattice energy of an ionic solid: the charge on the ions, and the radius, or size, of the ions. The effect of those factors is: as the charge of the ions increases, the lattice energy increases. as the size of the ions increases, the lattice energy decreases.
2:- Factor affecting of lattice enthalpy of ionic crystal
Higher the lattice energy, the greater is the tendency of the formation of an ionic bond. The higher the charges on the ions and the smaller the distance between them, the greater is the force of attraction between them
(a) size of the ions:- Smaller the size of ion more the lattice energy.
(b) charge on the ions :-Charge of ion -------- More the charge more the force of attraction, Stronger the ionic bond hence higher the lattice energy.
NaCl formation (Born-Haber cycle)
1 : -The +108.4 is the atomization enthalpy of sodium (Na solid →Na gas). We have to produce gaseous atoms of sodium so that we can use the next stage in the cycle.
2:-The +495.6 is the first ionization energy of sodium. Remember that first ionization energies go from gaseous atoms to gaseous singly charged positive ions(Na →Na+ + e-)
3 :-The +121 is the atomization enthalpy of chlorine (½ Cl2 →2 Cl atom). Again, we have to produce gaseous atoms so that we can use the next stage in the cycle.
4:-The -348.6 is the first electron affinity of chlorine (Cl + e- → Cl-). Remember that first electron affinities go from gaseous atoms to gaseous singly charged negative ions.
5 Na + ion and Cl- ion in gaseous state combine by electrostatic force And form crystal Lattices 1 mole of sodium chloride compound
The energy released during this process is called lattice enthalpy the lattice enthalpy of sodium chloride -78 7.6 kilo joule per mole
Overall energy change may be express as :-
Na (s) +½ Cl 2 ⟶ NaCl (s) ΔH = - 411.2 KJ/mol
- 411.2 = +108.4 + 495.6 + 121 - 348.6 + LE
LE = -411 - 107 - 496 - 122 + 349
ΔlatticeH͒ = + 787 .6 KJ/mol
General properties of ionic compound
1:- physical state :- Ionic compounds form solid crystals
2:-melting and boiling point :- Ionic Compounds have high boiling and melting points as they are very strong and require a lot of energy to break.
3:- Solubility :- Electrovalent compounds usually dissolve in polar solvent water and are insoluble in solvents like oil, petrol, kerosene
4:- electrical conductivity :- Ionic compounds do not conduct electricity in a solid-state but they do conduct electricity in the molten state and aqueous solution
5:- ionic reactions :- chemical reaction very fast
6:- non directional characteristic :- Electrical field is is non directional because each and surrounded by a positive charge ions in three dimensional crystal lattice
