Valency - Definition, Formula, Examples, Types, FAQs

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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.

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Define Valency .
Formula for valency:
Why do we need valency?
Valency and valence electrons:
How to find Valency:
Difference between valency and oxidation Number:
Types of valency:
Difference between atomicity and valency:

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:

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.

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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.

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.

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:

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.

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.

NCERT Chemistry Notes:

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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Frequently Asked Questions (FAQs)

1. What do you mean by valency variable or variable valency?

Variable valency of atoms refers to the fact that some items have more than one sort of valency of atoms. These compounds have one valency in one compound and a different valency in another. Iron, mercury, and copper are examples of elements with variable valency. The valency of transition items is varied.

2. Give one example of Variable Valency?

Iron has a valency of 2 in some compounds, such as ferrous sulphate (FeSO₄), and valency of 3 in others, such as ferric chloride (FeCl₃). There are two sorts of valencies in copper: 1 and 2. Mercury has two valency types: 1 and 2.

3. Why does the element of the same group have the same valency?

Because elements are arranged in increasing order of atomic number, the number of shells in each group increases by one, and the number of electrons increases from left to right in period, every element in the first group has one electron in their last shell, and every element in the second group has two electrons in their last shell, so all elements in the same group have the same valency.

4. Valency of Hydrogen is positive or negative?

Because hydrogen is non-metal and has an acidic nature, it receives electrons in order to achieve noble gas configuration, as after receiving one extra electron, it achieves the noble gas configuration of helium. However, due to the presence of one valence electron in its finals- Shell, hydrogen resembles alkali metals, which are basic in origin and have electropositive properties. Because hydrogen is similar to alkali metals, it can also contribute one electron. Hydrogen has both positive and negative valency in this way.

5. What is valency in chemistry?

Valency is the combining capacity of an atom or a group of atoms. It represents the number of chemical bonds an atom can form with other atoms. Valency is determined by the number of electrons an atom can gain, lose, or share to achieve a stable electron configuration.

6. How does the concept of valency apply to organometallic compounds?

In organometallic compounds, the valency of the metal atom determines how many organic ligands it can bond with. Understanding valency is crucial for predicting the structure and properties of these complex compounds.

7. Can you explain the concept of "satisfied valency"?

A satisfied valency occurs when an atom has formed the maximum number of bonds it can based on its valency. This often results in a stable electron configuration and is a key factor in determining the stability of chemical compounds.

8. How does valency influence the formation of coordination compounds?

In coordination compounds, the valency of the central metal atom determines its coordination number - the number of ligands it can bond with. Understanding valency is crucial for predicting and explaining the structures of these complex compounds.

9. Can you explain how valency influences the strength of chemical bonds?

Generally, atoms with higher valencies can form more bonds or stronger bonds. The number and type of bonds an atom can form, determined by its valency, directly influence the overall bond strength in a molecule.

10. What is the relationship between valency and atomic radius?

There's often an inverse relationship between valency and atomic radius. As you move across a period in the periodic table, valency typically increases while atomic radius decreases. This is due to increased nuclear charge and electron-electron repulsion.

11. Can you explain how valency relates to the concept of bond order?

Bond order represents the number of chemical bonds between a pair of atoms. It's closely related to valency, as the valency of atoms determines the maximum possible bond order between them in a molecule.

12. What is the relationship between valency and the periodic trends?

Valency often follows periodic trends. For example, in main group elements, valency typically increases across a period and decreases down a group. These trends are related to changes in atomic structure and electron configuration across the periodic table.

13. How does valency influence the reactivity of an element?

Valency often correlates with reactivity. Elements with higher valencies can form more bonds, potentially leading to greater reactivity. However, other factors like electronegativity and atomic size also play significant roles in determining reactivity.

14. How does the concept of valency apply to polyatomic ions?

For polyatomic ions, valency refers to the overall combining capacity of the entire ion. The valency of a polyatomic ion is determined by the total charge it carries, which influences how it combines with other ions or atoms.

15. How is valency different from oxidation state?

While valency represents the number of chemical bonds an atom can form, oxidation state indicates the degree of oxidation of an atom in a compound. Valency is always a positive number, whereas oxidation state can be positive, negative, or zero.

16. What role does valency play in understanding redox reactions?

In redox reactions, changes in oxidation states occur. Understanding the valencies of the elements involved helps in predicting and balancing these reactions, as it provides insight into the potential electron transfers.

17. Can you explain the concept of effective valency?

Effective valency is the actual combining capacity of an atom in a particular compound, which may differ from its typical valency. It takes into account factors like oxidation state and the specific chemical environment of the atom.

18. What is the relationship between valency and ionic charge?

For monatomic ions, the magnitude of the ionic charge is often equal to the valency. For example, an atom with a valency of 2 may form an ion with a charge of +2 or -2, depending on whether it loses or gains electrons.

19. Why do transition metals often exhibit multiple valencies?

Transition metals have partially filled d-orbitals, which can accommodate or release different numbers of electrons. This flexibility in their electron configuration allows them to form bonds with different numbers of atoms, resulting in multiple valencies.

20. How does the periodic table help in predicting valency?

The periodic table organizes elements based on their electronic configuration. Elements in the same group typically have the same number of valence electrons, which often leads to similar valencies. The position of an element in the periodic table can provide insights into its likely valency.

21. Why do elements in the same group often have the same valency?

Elements in the same group have similar electron configurations in their outermost shell. As valency is determined by the number of electrons an atom can gain, lose, or share, elements in the same group tend to have the same valency due to their similar outer electron arrangements.

22. Why do hydrogen and alkali metals typically have a valency of 1?

Hydrogen and alkali metals have one electron in their outermost shell. They tend to lose this single electron to achieve a stable electron configuration, resulting in a valency of 1.

23. How does valency influence the formation of complex ions?

The valency of a central metal ion in a complex determines how many ligands it can coordinate with. This directly affects the structure and properties of the complex ion, including its stability and reactivity.

24. Can you explain how valency relates to the concept of resonance?

Resonance occurs when multiple valid Lewis structures can be drawn for a molecule. The valency of the atoms involved determines the possible arrangements of bonds, influencing the number and types of resonance structures that can exist.

25. Can an element have multiple valencies?

Yes, some elements can exhibit multiple valencies. This occurs when an element can form different types of bonds or participate in various chemical reactions. For example, iron can have a valency of 2 (ferrous) or 3 (ferric).

26. How does valency differ between metals and non-metals?

Metals typically have positive valencies as they tend to lose electrons, forming cations. Non-metals usually have negative valencies as they tend to gain electrons, forming anions. This difference arises from their electronic configurations and positions in the periodic table.

27. What is meant by variable valency?

Variable valency refers to the ability of an element to exhibit different valencies in different compounds. This often occurs in transition elements, where multiple stable electron configurations are possible, leading to various bonding capacities.

28. Why do noble gases typically have zero valency?

Noble gases have a complete octet (eight electrons) in their outermost shell, making them extremely stable. As a result, they generally do not need to gain, lose, or share electrons, leading to a valency of zero under most conditions.

29. Can valency change in different chemical environments?

Yes, the valency of an element can change depending on the chemical environment. Factors such as temperature, pressure, and the presence of other reactants can influence the valency an element exhibits in a particular reaction.

30. What is the relationship between valency and the octet rule?

The octet rule states that atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their outermost shell. Valency is often determined by how many electrons an atom needs to gain, lose, or share to fulfill the octet rule.

31. How does valency affect the stability of chemical compounds?

Compounds formed by atoms combining according to their valencies are generally more stable. The satisfaction of valencies often leads to completed electron shells, which contributes to the overall stability of the compound.

32. How is valency related to the concept of electron affinity?

Electron affinity is the energy change when an atom gains an electron. Elements with high electron affinity often have higher valencies for forming anions, as they can more easily accept electrons to complete their octet.

33. How does valency relate to the formation of coordinate covalent bonds?

In coordinate covalent bonds, one atom provides both electrons for the bond. The atom donating the electron pair often has a lone pair of electrons, which is related to its valency. Understanding valency helps predict which atoms can form coordinate covalent bonds.

34. How does valency relate to the concept of electronegativity?

Electronegativity is the ability of an atom to attract electrons in a chemical bond. Elements with high electronegativity often have higher valencies for forming anions, as they can more easily attract and hold additional electrons.

35. What role does valency play in chemical formulas?

Valency is crucial in writing and balancing chemical formulas. The subscripts in chemical formulas represent the ratio of atoms, which is determined by their respective valencies. Understanding valency helps in predicting and writing correct chemical formulas.

36. What is the significance of valency in predicting chemical behavior?

Understanding valency helps predict how elements will combine, what types of compounds they can form, and their likely chemical behavior. It's a fundamental concept for understanding chemical reactions and molecular structures.

37. How does valency affect chemical bonding?

Valency directly influences how atoms bond with each other. It determines the number of bonds an atom can form and, consequently, the types of compounds it can create. Atoms combine in ratios that satisfy their respective valencies.

38. How does valency influence the geometry of molecules?

Valency determines the number of bonds an atom can form, which directly affects molecular geometry. The arrangement of bonds around a central atom, influenced by its valency, determines the overall shape and spatial orientation of the molecule.

39. Can you explain how valency relates to the concept of hybridization?

Hybridization involves the mixing of atomic orbitals to form new hybrid orbitals. The number of hybrid orbitals formed is often related to the valency of the atom, as it determines the number of bonds the atom can form.

40. How does valency influence the formation of double and triple bonds?

Elements with higher valencies can form multiple bonds. For instance, carbon with a valency of 4 can form single, double, or triple bonds. The ability to form these multiple bonds is directly related to the valency of the atoms involved.

41. How does valency affect the solubility of compounds?

Valency influences the type and strength of bonds formed in a compound, which in turn affects its solubility. Compounds with higher valency atoms often form stronger bonds, which can impact their solubility in different solvents.

42. What is the significance of valency in understanding isomerism?

Valency plays a crucial role in structural isomerism. The different ways in which atoms can satisfy their valencies while maintaining the same molecular formula leads to various structural isomers.

43. How does valency relate to the concept of formal charge?

Formal charge is calculated based on the difference between the number of valence electrons in a free atom and the number of electrons assigned to it in a Lewis structure. Understanding valency is crucial for accurately determining formal charges.

44. How does valency affect the reactivity of functional groups in organic chemistry?

In organic chemistry, the valency of atoms in functional groups determines their bonding capabilities and, consequently, their reactivity. Understanding valency helps predict how different functional groups will behave in chemical reactions.

45. How does valency influence the formation of metallic bonds?

In metallic bonding, the valency electrons of metal atoms are delocalized to form an "electron sea." The number of valence electrons, determined by the valency, affects the strength and properties of the metallic bond.

46. How does valency affect the acid-base properties of compounds?

The valency of atoms in a compound can influence its acid-base properties. For example, the valency of the central atom in an oxoacid often determines its strength, with higher valencies generally leading to stronger acids.

47. What role does valency play in understanding chemical equilibrium?

Valency helps in predicting the possible products in a chemical reaction and understanding how reactants combine. This is crucial for writing balanced equations and understanding the stoichiometry involved in chemical equilibrium.

48. How does valency influence the formation of hydrogen bonds?

Atoms with high electronegativity and at least one lone pair of electrons (related to their valency) can form hydrogen bonds. Understanding valency helps predict which molecules can participate in hydrogen bonding.

49. Can you explain how valency relates to the concept of oxidation number?

Oxidation number and valency are related but distinct concepts. While valency represents the combining capacity of an atom, oxidation number represents the degree of oxidation of an atom in a compound. However, in many cases, the magnitude of the oxidation number equals the valency.

50. How does valency affect the formation of crystal structures?

The valency of atoms determines how they can bond with each other, which directly influences crystal structure. The arrangement of atoms in a crystal lattice is often a result of how atoms satisfy their valencies while maximizing stability.

51. What is the significance of valency in understanding molecular orbital theory?

Valency helps predict the number of molecular orbitals formed when atoms combine. The number of valence electrons, determined by valency, influences the filling of bonding and antibonding molecular orbitals.

52. How does valency relate to the concept of electrochemical equivalence?

Electrochemical equivalence, which is the mass of a substance deposited or liberated at an electrode during electrolysis, is directly related to the valency of the ion involved. Understanding valency is crucial for calculations in electrochemistry.

53. Can you explain how valency influences the formation of cluster compounds?

In cluster compounds, multiple metal atoms bond together. The valency of these metal atoms determines how many bonds they can form within the cluster and with surrounding ligands, influencing the overall structure and properties of the cluster compound.

54. How does valency affect the formation and properties of polymers?

The valency of atoms in monomers determines how they can link together to form polymers. It influences the type of polymer formed (linear, branched, or cross-linked) and consequently affects the polymer's properties such as strength, flexibility, and melting point.