Valency - Definition, Formula, Examples, Types, FAQs

Define Valency .

Valency Definition Chemistry and Valence meaning: An element's valence chemistry, also known as valency, is a measure of its ability to combine with other atoms to create chemical compounds or molecules. The number of hydrogen atoms that an atom of a certain element may combine with determines its combining capability, or affinity. Carbon has a valence of 4 in methane; nitrogen has a valence of 3 in ammonia; oxygen has a valence of 2 in water; and chlorine has a valence of 1 in hydrogen chloride. The number of hydrogen atoms that can be combined with a binary hydride element or twice the number of oxygen atoms that can be combined with the oxide or oxide elements in a binary hydride.

Formula for valency:

The valence of a particular atom present in a molecule is the number of electrons that an atom utilises in the formation of a bond, according to another current valence definition. The formulas for calculating the valence represent this. The following electrons can also be used to define valence:

Number of electrons in the last/valence shell of a free atom - Number of electrons on an atom in a non-bonded molecule. As a result, the formula for valency definition in chemistry is Valence or Valency = Number of bonds created + Formal charge of the atom.

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Why do we need valency?

The main concept of needing valency is that The letters K, L, M, N, and so on stand for the orbitals (shells) in which electrons in an atom are organized. Valence electrons are the electrons in an atom's outermost shell/orbit. Valence electrons play a role in any chemical reaction because the outermost orbit usually contains more energy than the electrons in other orbits. The Bohr-bury system states that an atom's outermost orbit can have up to 8 electrons. The element, on the other hand, has very little to no chemical activity when the outermost orbit is completely filled. Their ability to combine is reduced to nil or non-existent. Noble gases are the least reactive because their outermost orbit is totally filled. The ability of other elements to form noble gas configurations, on the other hand, determines their reactivity. It will also help determine the valency of an atom.

Valency and valence electrons:

The amount of bonds that an element may create is measured by its valency. The electrons that are available to participate in this bonding are known as valence electrons. The main difference between valency and valence electrons is that valency refers to the number of bonds that an atom or element can create, whereas valence electrons refer to the electrons that participate in these bond forms. Because they have numerous valencies, they are frequently found in the outermost shell of main group elements and can even be found in the closed shells of transition metals.

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How to find Valency:

In the periodic table, the valency of the same group of elements is the same. If we look at the periodic chart, we can see that all of the elements in group 8 have completely occupied their outermost orbits and have achieved octet organisation. As a result, the valencies of the elements in group 8 are zero. Any element's valency can be determined using one of three methods:

1. Octet rule: This rule indicates that atoms of an element or chemical have a tendency to gain or lose 8 electrons in their outermost orbit in whatever form of the compound they are present in. In its outermost orbit, an atom can have up to 8 electrons.

   If an atom has one to four electrons in its outermost orbit, it is more likely to lose them. Positive valency is achieved when an atom contributes its free electrons. If an atom contains four to seven electrons in its outermost orbit, it will gain electrons. In such instances, accepting an electron rather than contributing one is preferable. As a result, the valency is calculated by subtracting the number of electrons from 8. Only helium does not have eight electrons in its outermost shell.

Example: Sodium has one valence electron, by giving up one electron sodium can gain its Noble electronic configuration, thus sodium donates its one valence electron, thus the valency of sodium becomes 1.

2. Using periodic table: The periodic table graphic is used to calculate valency in this method.

For example, all metals in column 1 have valency +1, including hydrogen, lithium, sodium, and so on. Similarly, all of the elements in column 17 have a valency of -1, such as fluorine and chlorine.

3. From the chemical formula: This rule is based on the octet rule, and the valency of an element can be determined by examining how it is combined. Example: NaCl, We know that sodium (Na) has a +1 valency and chlorine (Cl) has a -1 valency. To establish a stable outermost orbit, both sodium and chlorine must gain one electron and lose one electron, respectively. As a result, sodium provides one electron whereas chlorine accepts it. This is how valency is calculated.

Difference between valency and oxidation Number:

The valency of an atom refers to its ability to combine different elements. As a result, it is the number of valence electrons that an atom must obtain or lose from its outermost orbit. The charge that an atom can carry is determined by its oxidation number. Nitrogen, for example, has a valency of 3 but an oxidation number that can range from -3 to +5. The presumed charge of a certain atom in a molecule or ion is known as the oxidation number. It aids in determining an atom's ability to gain or lose electrons within a certain species.

Types of valency:

1. Electrovalency: Ionic compounds, also known as electrovalent compounds, are formed when metal ions and non-metal ions combine. Sodium chloride, for example (NaCl). The metal in this chemical is sodium (Na), and the non-metal is chloride (Cl). It is made up of electrons that have been transferred. Electrovalency refers to the chemical connection between metal and non-metal ions, and these compounds are known as electrovalent compounds. The quantity of electrons lost or gained by the atoms in an ionic molecule is known as electro valency.

Example: NaCl is an ionic compound, the reactions are:

Na→Na⁺+1e^-

Cl+1e^-→Cl^-

Na⁺+Cl^-→NaCl

In the case of sodium chloride (NaCl), the electro valency of sodium (Na) and chloride (Cl) is 1, because sodium loses one electron and the chloride ion gains one.

2. Covalency: Covalent compounds are non-metal compounds created through chemical bonding. The sharing of electrons between atoms creates these compounds.

Covalent compounds of non-metal + non-metal.

The number of bonds by which an atom is physically connected to another atom is known as the valency of these compounds. Covalency is present in these substances.

Example: Fluorine has a valence electron count of seven. It can share one electron with another fluorine atom to make F₂ or with a hydrogen atom to complete its octet to form HF, hence its covalency is 1.

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Difference between atomicity and valency:

The number of atoms in a molecule is known as atomicity. The maximum number of electrons that an atom must lose, gain, or share in order to become stable is called valency. The primary distinction between atomicity and valency is that atomicity specifies a molecular characteristic, while valency describes an elemental attribute. Depending on the atomicity of molecules, they can be categorized into groups. Molecules can be monatomic, diatomic, triatomic, or polyatomic, for example, Elements like Helium and argon are monatomic compounds. Oxygen (O₂)and Nitrogen (N₂)are diatomic compounds.

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