What does the term ‘Valency’ mean?
The valency of an element is a measure of its combining capacity and can be defined as
the number of electrons that must be lost or gained by an atom to obtain a stable electron configuration.
What does the term ‘Oxidation State’ mean?
The oxidation state of an atom is the number of electrons lost or gained by it.
Oxidation State and valency are one of the most fundamental properties of elements and can be studied with the help of electron configurations.
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Valency and Oxidation State
Electrons that are found in the outermost shell are generally known as valence electrons and the number of valence electrons determines the valency (or valence) of an atom.
- The valencies of the elements belonging to the s-block and the p-block of the periodic table are generally calculated as the number of valence electrons or eight minus the number of valence electrons.
- For the d-block and f-block elements, valency is determined not only on the basis of valence electrons but also on d and f orbital electrons. However, the general valencies of these d and f block elements are 2 and 3.
The general oxidation state of the elements of the periodic table is illustrated in the chart provided below.
Valency of First 30 Elements
The valency of the first 30 elements of the periodic table is given below.
| Element | Atomic Number | Valency |
| Valency of Hydrogen | 1 | 1 |
| Valency of Helium | 2 | 0 |
| Valency of Lithium | 3 | 1 |
| Valency of Beryllium | 4 | 2 |
| Valency of Boron | 5 | 3 |
| Valency of Carbon | 6 | 4 |
| Valency of Nitrogen | 7 | 3 |
| Valency of Oxygen | 8 | 2 |
| Valency of Fluorine | 9 | 1 |
| Valency of Neon | 10 | 0 |
| Valency of Sodium (Na) | 11 | 1 |
| Valency of Magnesium (Mg) | 12 | 2 |
| Valency of Aluminium | 13 | 3 |
| Valency of Silicon | 14 | 4 |
| Valency of Phosphorus | 15 | 3 |
| Valency of Sulphur | 16 | 2 |
| Valency of Chlorine | 17 | 1 |
| Valency of Argon | 18 | 0 |
| Valency of Potassium (K) | 19 | 1 |
| Valency of Calcium | 20 | 2 |
| Valency of Scandium | 21 | 3 |
| Valency of Titanium | 22 | 4 |
| Valency of Vanadium | 23 | 5,4 |
| Valency of Chromium | 24 | 2 |
| Valency of Manganese | 25 | 7, 4, 2 |
| Valency of Iron (Fe) | 26 | 2, 3 |
| Valency of Cobalt | 27 | 3, 2 |
| Valency of Nickel | 28 | 2 |
| Valency of Copper (Cu) | 29 | 2, 1 |
| Valency of Zinc | 30 | 2 |
Periodic Trends in the Oxidation States of Elements
1. Variation Of Oxidation State Along a Period
While moving left to right across a period, the number of valence electrons of elements increases and varies between 1 to 8. But the valency of elements, when combined with H or O first, increases from 1 to 4 and then it reduces to zero. Consider two compounds containing oxygen Na2O and F2O. In F2O, the electronegativity of F is more than oxygen. Hence, each of F atom will attract one electron from oxygen i.e. F will show -1 oxidation state and O will show +2 oxidation state. Whereas, in the case of Na2O, oxygen is highly electronegative than sodium atom. So oxygen will attract one electrons from each sodium atom showing -2 oxidation state and Na will have +1 oxidation state. The oxidation state of the element represents the charge possessed by an atom due to the loss or gain of electrons (due to the electronegativity difference between the combining atoms) in the molecule.
2. Variation Of Oxidation State within a Group
As we move down in a group the number of valence electrons does not change. Hence, all the elements of a particular group group have the same valency.
Guidelines for assigning the Oxidation States
- Oxidation states of elements like O2, S8, H2, P4, Fe, etc are zero.
- Oxygen has an oxidation state of -2. But in its peroxides like Na2O2 and H2O2, it has -1 as its oxidation state
- Similarly, hydrogen has +1. But in Metal Hydrides, such as NaH, LiH, etc, it has -1
- Some elements have the same oxidation states as in their compounds such as
- Halogens have -1 except when they form a compound with one another or Oxygen.
- Alkali Metals such as Na, K, Rb, Li, Cs have +1
- Alkali Earth Metals have +2 such as Mg, Ca, Ba, Be, Sr, etc
Frequently Asked Questions – FAQs
What is a valency?
Valency is defined as the number of hydrogen atoms which combine directly or indirectly with one atom of an element. Example: One atom of nitrogen combines with three atoms of hydrogen to form ammonia gas. So, the valency of nitrogen is 3.
What is carbon valency?
The valency of carbon is four and one atom of carbon can make four covalent bonds.
What is Tetravalency?
Carbon has a valency of four, so it is capable of bonding with four other atoms of carbon or atoms of some other monovalent element. This is known as tetravalency of carbon.
Does valency have a charge?
Charge is the value that is attained when an atom loses or gains electrons; this also happens to satisfy the octet rule. Valency is defined for elements whereas charge is defined for loss. So, valency cannot be related to charge.
How do you write the valency of oxygen?
Atomic Number of oxygen is 8. electronic Configuration of oxygen= 2, 6. So the valency is 8-6 = 2.
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What is the Valency of Mercury?
The Valency of Mercury is 2, 1.
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what is the atomicity of mercury
Atomicity of mercury vapour is 1.
Thanks for giving this chart it is very helpful for me
Which of the following elements can exhibit a valency greater than 4
a) Boron b) Phosphorous c) Chlorine d) Flourine
The valency of fluorine is seven. This means that the outer electron shell of a fluorine atom contains seven electrons.
Phosphorus
Phosphorous has valency 3: With three unpaired electrons in three p orbitals, phosphorous show’s valency 3. Click here to learn more about Phosphorous.
So helpful
What is the vallency of carbon?
Valency of carbon is 4.
what is meant by anomalous properties?
Anomalous behaviour of an element refers to the deviation of the properties and behaviour of an element from its usual or normal behaviour.
How to calculate the mole value of an element??
Click here to calculate the mole value.
Which valency must we consider for copper and iron
Iron has two valencies Fe+2 and Fe+3. Copper has two valencies: +1 and +2 and the corresponding atoms are termed as Cuperous (+1 valency) and Cupric (+2 valency)
how do we find valency of any electrons
The valency of the atom of an element is determined by the number of electrons in its outermost shell, i.e. valence shell.
Whar is valency of mercury?
Hg has a valency of +1 and +2 in +1 valency it’s called mercurous and in +2 valencies it’s called mercuric! Actually The Valency of Mercury (Hg) is variable. In HgCl2 the Valency is different and in Hg2Cl2 valency is different.
It’s very helpful for me
What is the maximum number of electrons in the 3rd shell??
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.
What is Positive and Negative Valency?
Depending on whether the atom loses, gains or shares electrons, the valency may be positive or negative or neutral respectively.
What is valency
The combining capacity of an atom is known as its valency. The number of bonds that an atom can form as part of a compound is expressed by the valency of the element.
What is the atomicity of sodium
Atomicity of sodium is 1 and hence it is called a monoatomic molecule.
Nice and neat table. Helped me a lot in writing and balancing equations.
What is the Valency of manganese how to find it
Valency of Manganese is 7, 4, 2.
Manganese is a transition metal, meaning that it can have more than one valence state. Its electron configuration is [Ar] 3d5 4s2. The two electrons in the 4s orbital are obvious valence electrons, so a valence state of 2+ is possible.
who invented valency
The first great step in the development of a satisfactory explanation of valence and chemical combination was made by the American chemist G.N. Lewis (1916) with the identification of the chemical bond of organic compounds with a pair of electrons held jointly by two atoms and serving to hold them together.
What is valency .
The combining power of an element, especially as measured by the number of hydrogen atoms it can displace or combine with.
How to find the valency .
If the number of electrons in the outer shell is between one to four, the compound is said to have positive valency. For compounds with electrons four, five, six, or seven, the valency is determined by subtracting the electron from eight. All noble gases except for Helium have eight electrons.
What is atomicity ?
Atomicity is defined as the total number of atoms present in a molecule. For example, each molecule of oxygen is composed of two oxygen atoms. So atomicity of oxygen is 2. Atomicity is sometimes used in the same sense as valency.