What is Electrovalency and How to Find? – Best Guide!

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Electrovalency is the chemical bonding type, that occurs by transferring electrons from a metallic atom to a non-metallic atom. As a result of that, each atom can stable by taking its nearest noble gas electron configuration. Because of reducing and gaining electrons, the formation of oppositely charged ions happens. As a result of the electrostatic force between these oppositely charged ions, they form an electrovalent compound. This is the simplest way to define Electrovalency.

To understand this, We shall first consider a specific case of electrovalent combination between sodium and chlorine.

Electrovalency of Sodium and Chlorine

A sodium atom contains 11 nuclear protons and has the electron structure 2, 8, 1. It differs from the nearest rare gas electron configuration, that of neon, 2, 8, by the presence of one extra electron in the third orbit.

Also, A free chlorine atom contains 17 nuclear protons and has the electron configuration 2, 8, 7. It differs from the argon electron configuration, 2, 8, 8, by a deficiency of one electron in the third orbit.

Combination of Sodium and Chlorine

So, during the chemical combination of the sodium and chlorine atoms, the single electron from the outermost orbit of the sodium atom passes over to the outermost orbit of the chlorine atom. Therefore way, two ions are produced. The sodium ion is positively charged, as Na+, by the nuclear proton left in excess after the departure of the electron. Therefore, the electron structure is now 2, 8. Secondly, the chlorine ion is negatively charged, as Cl-, by the acquired electron. Therefore its electron configuration is now 2,8, 8.

combination of na and cl in electrovalency

In both cases, the ions now have the electron configuration of a rare gas (neon and argon, respectively) with the external electron octet. They differ, however, from the neutral atoms of these noble gases by carrying their respective ionic charges.

No molecule is formed in electrovalent combination

Electrovalency of NaCl

Any experimental quantity of sodium chloride contains an enormous number of chlorine and sodium ions in equal proportions. The electrical attraction resulting from their opposite charges constitutes such a chemical ‘bond’ that exists at all. The ions arrange themselves into a crystal lattice. So, in this case, a face-centered cube. But there is no specific airing of ions, which could be considered as a molecule of sodium chloride. The change during combination expresses diagrammatically in the figure below. Energy must supply to remove the electron from the sodium atom and energy is liberated as it enters the chlorine structure.the net result of these two changes in the liberation of heat energy to the surroundings, and the reaction is exothermic, as:

Na + Cl2 -> Na+Cl   ; 97,700 cals, liberated.

The main features of Electrovalency of sodium chloride stated above are common o all cases of electrovalent combination. The number of electrons lost from or added to the outermost layer of the atom during combination is equal to its operative valency.

structure of electrovalent nacl

This is positive for metallic elements, which lose electrons and negative for non-metals, which accept electrons.

The number of ions involved must balance the valency requirements of the elements, as in the following cases. Note that only the outermost electron layer is concerned in the chemical reaction.

Formation of electrovalent compounds
Formation of electrovalent compounds

Note, in all these cases, reversion to the electron structure of a rare gas during combination. Also the production of external octets of electrons.

Properties of electrovalent compounds

  1. Electrovalent compounds contain no molecules. They are aggregates of ions. If the ions made mobile by dissolving the compound in the water or by melting it, the resulting solution or melt would conduct electric current with decomposition. Therefore electrovalent compounds are electrolytes.
  2. The electrical forces between the oppositely charged ions are powerful. Consequently, electrovalent compounds form comparatively rigid crystal lattices and are solids. They melt at high temperatures. (compared to simple covalent compounds). Also, they are non-volatile.
  3. Electrovalent compounds are rarely soluble in organic liquids. (which are usually covalent). But many of them dissolve in water.

The principal types of electrovalent compounds which present Electrovalency are,

  1. Almost all salts.
  2. Solid alkalis, metallic oxides, and hydroxides.
  3. The mineral acids in dilute solution.

Factors Favouring Electrovalency

In general, the conditions favoring ion formation are:

  • A large atom to form a cation and small atom to form an anion. This is because a cation is formed by the loss of electron(s). by the inverse-square law, electrons are more loosely held in the outer layer of large atoms in which the attracting nucleus is comparatively distant. So, ionization is easier. Thus lithium is least, and cesium the most, easily ionized of the alkali metals.

On the other hand, an ion is formed by electron gain. By the inverse square law, electrons are more powerfully attracted to the smaller atoms in which the positive nucleus is relatively close. The principal elements forming anions are the halogens, F, Cl, etc., oxygen, O, and Sulphur, S. Anions with three added electrons are unknown. Uin the halogens, the least complex atom, fluorine, most readily forms an ion. Thus, aluminum fluoride is electrovalent, while the anhydrous chloride is covalent. The greater size, and lower ionizing tendency, of the chlorine atom, explain this.

  • The ion, when formed, should have a stable structure. The most stable structure is the outer octet or duplet of electrons. In the more complex atoms, an 18-electron layer may serve a similar purpose. For example, the zinc atom (2, 8, 18, 2) loses the outer electron layer to give a divalent ion, Zn++. The above ideas are part of Fajan’s Rules.

Electrovalency : Conclusion

So from this article, I think you gained good knowledge about,

  • What is Electrovalency?
  • How to find it?
  • Conditions that are favoring and
  • Examples of electrovalent compounds as well.

 Read another very important article which is related to this topic: Electronegativity Trend

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