What Are Valence Electrons? Presence of electrons in outer shell of an atom. The outer most shell of an atom play vital role in the chemical bonding. One or more than one electrons can be part of valence shell. An atom loss or gain electrons to complete its valency, in order to gain stability. Lack of stability leads to various chemical reactions and bonding between a number of metals and non metals. Here in this article, we will discuss the role of valence electron(s) in chemistry.
Importance Of Valence Electrons:
Valence electrons are of great importance in chemistry. They are located in outer shell of an atom. They are special and unique, because they are at the front line when, any chemical reaction take place.
Electronic Configuration:
The arrangement of electrons into shells and sub shells is called electronic configuration. This configuration make study of electrons easy and feasible. Every shell, has a different to carry electrons. Certain rules are present in chemistry which are helpful in electronic configuration. When shell one is considered, it can hold maximum two electrons.
Electrons Accommodation:
The shell number two has capacity to carry six electrons. Shell number 3, has ability to carry 10 electrons. When we study the elements of periodic table, we will find different elements in systemic arrangement. The Ist element of periodic table is hydrogen, which has one electron in outer most shell. It shows that, hydrogen has ability to loss one electron.
1. Magnesium:
Furthermore, When we came to see the valence shell of magnesium, It has two electrons in outer shell. It total electrons are 12. Out of which two become part of inner shell, 8 become part of second shell and remaining two are placed in outer shell.
Duplet Rule:
It is a rule, which states that, the stability of an atom would be ensured in that time, when it has two number of electrons in outer shell. To fulfill duplet rule, an element can gain or loss electrons by participating in chemical bond. the main purpose of this rule was to explain the stability of an atom. This rule is mostly applicable for those atoms, for which octet rule is not applicable. Some Examples are as follow:
1. Hydrogen:
Hydrogen, Lithium and Helium are those elements, which strictly follow this rule. In case of hydrogen, it loss or shares electron to fulfill duplet rule.
2. Lithium:
Besides, lithium loses an electron to gain stability. Some limitations are associated with the application of duplet rule. There are a lot of elements in periodic table, which are stable but have more than two electrons in outer shell.
3. Helium:
Likewise, there are also some elements which have two electrons in last shell, but are not guaranteed as stable elements. On behalf of these limitations, chemists think of another rule to define the stability of an atom. The application of duplet rule in determining the stability of helium is inevitable. This rule also justify the participation of hydrogen in chemical reactions.
Octet Rule:
This rule defines the stability of atoms in different prospective. According to this rule, there should be eight electrons in valence shell to ensure the stability of atoms. Octet rule, is mostly applicable to the main group elements which participate in chemical bonding. Those elements, which obey octet rule are halogens, oxygen, nitrogen and carbon.
S And P Block Elements:
These elements mostly belong to s and p block of periodic table. When oxygen and carbon reacts to form carbon dioxide, they follow octet rule to attain stability. They shared electrons with each other to fulfil the need of valency. The noble gases of periodic table are also follower of octet rule. They are most stable elements in nature, which not participate in any chemical reaction thus, designated as inert gases.
Stability:
Ionic bond exists between the sodium and chlorine in NaCl, which ensure the stability of both atoms. As chlorine atom has seven electrons in valence shell. To complete its octet, it will form bond with sodium atom, which is having one electron in last shell. Thus, In this sodium loss electrons to fulfil octet rule and chlorine will gain that one electron to become stable.
Electrons Sharing:
In case of magnesium oxide, octet rule is followed by the participants. The outer shell of Mg contains tow electrons, therefore it will loss the two electrons and transferred them to oxygen atom, which is willing to accept two electrons to complete the octet. This lead to the formation of ionic bond between the two atoms.
Limitations:
Some limitations and exceptions are also associated with octet rule. Free radicals are supposed to not follow this rule, as they contain unpaired electrons. Some elements are in accordance with duplet rule, so you can’t apply octet rules for them. Some transition elements also disobey this rule due to presence of d orbitals.
How To Find Electrons?
To determine the number of electrons an atom is having is outer most shell, one can simply count electrons in outer most shell. Counting is a time consuming task. You can simply follow the electronic configuration to decide the number of electrons. For this purpose, divide the electrons among shells and sub shells of the atom, according to the capacity of of each shell. Then see the number of electrons in last shell, to access the valency of that atom. Whether, that atom can gain or loss electrons to obey any of the above mentioned rule. A quick visit to periodic table also help in the determination of valence electrons.
Periodic Table:
It is the systemic and proper arrangement of elements in groups, sub groups , periods and block on the basis of increasing atomic number and on behalf of other properties. When we move from left to right in periodic table, the elements are arranged on the basis of increasing atomic number.
Groups In Periodic Table:
Four categories of elements are common in periodic table. Which include, main group elements, transition elements and inner transition elements. The columns are referred as groups, which are 18 in numbers. The rows are known as periods, which are 7 in numbers.
Left To Right In Periodic Table:
In order, to find number of valence electrons , move from left to right, as the valance electron increase by one from one group to the second one. In same way, when we move form top to bottom, the number of valence electrons remain same, but the atomic size increase. Because number of shells increase. In periodic table, the period number shows number of shells an element have. While as the group number change, it shows the number of electrons in valence shell.
Transition Elements:
Transition elements are those, which participates in chemical reaction by involving their valence electrons. They have properties similar to metals like they are ductile, have shiny surface, can conduct electricity easily. You will find all transition elements in the middle of periodic table between the main group elements. The number of such elements in table is 24. when features of such elements are considered, they are hard and strong, have high density, the melting and boiling point is also high. Some elements of transition group, are of great importance at industrial level.
1. Alloys:
Like copper, iron are used for electrical purpose. These metals are used to form alloys. Elements like gold ,silver have capacity to dissolve mineral acids. In the transition group, there is sub division of elements into Ist, 2nd and 3rd transition series on the basis of electronic structure. We are commonly using iron in our daily life.
2. Iron:
As iron is a transition metal. We use it in construction of buildings, ships and automobiles. Moreover it usage is common in cosmetics, fertilizers. Iron is also part of our body. The blood which is circulating all nutrients in our body contains iron in its hemoglobin. Likewise, copper is also used in electronics, because it is good conductor of electricity. It is also used in other appliances and cooling system.
Summary:
Valence electrons play a vital role in the stability of an atom. Different types of chemical reactions in our surrounding are possible due to the contribution of valence electrons. They are at the front line, when any chemical reaction takes place. Different rules have been implemented for the proper arrangement of electrons in shells and sub shells. The duplet rule defines, the accommodation of two electrons in the shell, while according to octet rule, there should be 8 electrons in the outer shell, in order to gain stability. These rules are associated with some limitations. Because there are some elements either they not follow octet or duplet rule.
Chemical Bonding:
. In every chemical reaction, an atom has to donate its valence electrons to make linkage with other atoms. Some atoms are supposed to loss electrons while other atoms are there to gain electrons.
Ionic Bonding:
It is such type of linkage which is formed, when an electron from one atom is completely transferred to other atom. Basically, this type of bonding is due to electrostatic force of attraction between two oppositely charged atoms. It is also known as electrovalent bond. The atom gained positive charge which loss its electron, while the acceptor become negatively charged. Ionic bond is very common between metals and non metals.
Strong Bond:
This bond will not form until such atoms come in contact which are having big difference in electronegativities. Ionic bond is considered as a strongest bond. High energy is needed to break this type of bonding. The melting and boiling points are also high for the ionic compounds. When ionic compounds are in aqueous solution, they become able to conduct electricity very efficiently.
Ionic Compounds:
We are using a number of compounds in our daily life which are ionic in nature. Sodium chloride compounds, sodium carbonates, sodium hydroxide and sodium hypochlorite. These compounds are of great importance.
1. Sodium Chloride:
This ionic compound is commonly known as table salt. It is part of many minerals and sea water. It is widely used in field of medical. It is used to balance the fluid in our body. It balance the level of electrolytes in our body. Loss of electrolytes can cause dehydration. It is in commonly used for the preservation of processed food. In hospitals, saline solution of NaCl is used to reduce dehydration. Moreover, it excess usage is really hazardous for health. It will cause tremendous increase in blood pressure which lead to chronic heart diseases.
2. Sodium Hypochlorite:
It is also an ionic compound used as disinfectant. It is used to kill all sort of germs on any surface. Mostly, it is used on skin wounds and infection. It is used during and after surgery to treat the wounds. You can use sodium hypochlorite in diluted .
Covalent Bonding:
It is such type of bonding between atoms which is formed as result of sharing of electrons. There is not complete transfer of electron from one atom to other. The pair of electrons which are shared between atoms are known as shared pair. The alternate name of covalent bond is molecular bonding. Electrons are shared among atoms to ensure the stability of the participating atoms in the chemical reaction. The shared electrons will contribute to their stability.
Linkage:
Those elements, which have high ionization energy are suitable for making covalent linkage. Because, high ionization energy make transfer of electrons difficult. While those elements, which have low electron affinity are unable to accept electrons, therefore, such elements prefer to make covalent bonding.
Biomolecules Formation:
Covalent bond can be formed between the atoms of same elements like between two hydrogen atoms, two chlorine atoms. It can also occurs between the atoms of different kind i.e methane, water and ammonia. Those compounds which are formed due covalent bonding have low melting and boiling points. Moreover, such compounds need less energy to break. They would be bad conductor of heat and electricity.
Carbon Covalent Bonding:
When we look into the electronic configuration of carbon, it has to loss or gain four electrons to gain stability. A element will never want to loss four electron’s at a time. There is no any other element which will gave four electrons to carbon. Therefore carbon will shares electrons to form covalent bond. In this way, carbon will retain its stability.
Single Covalent Bond:
As the name suggests, single bond will form, when one pair of electron is shared between two atoms. This type of bonding is less denser and weaker as compared to other types of bonding. When we look into to the chemical bonding in HCL, there is formation if single bond. Hydrogen atom has one valence electron. Hydrogen will shares this one electron with one chlorine atom. In this way one pair of electron is shared between the participating atoms forming single covalent bond.
Double Bonds:
When two pairs of electrons are shared between the atoms then, the bond formed is called[double bond. This type of bond is strong but less stable. Carbon dioxide is a molecule which contains double bonds. One carbon atom has six valence electrons, while the two atoms of oxygen which are participating in the reaction having the valency of four.
Sharing Of Electrons:
In order to complete the octet, carbon shares two of its electron with one oxygen atom. in return oxygen shares two of its electrons with carbon to ensure the stability. Thus as a result, double bond is formed. The formation of oxygen molecule is also a product of double bonding. Two atoms of oxygen share two electron pairs between each other and form a stable oxygen molecule.
Triple Bonds:
Three pairs of electrons of electrons are shared between atoms forming a triple bond. This bond is strong but least stable. In the formation of nitrogen molecule, three pairs of electrons are shared between two nitrogen atoms. As nitrogen has five electrons in valence shell. So it will prefer to share three pairs of electrons , to achieve stability.
Polar Covalent Bond:
When there is a electronegativity difference between the participating atoms, then electrons are shared unequally between the atoms leading to formation polar bond. The atom with greater electronegativity will pull the shared electrons towards its side , which results in the formation of negative charge on the more electronegative atom and positive charge on the least electronegative atom.
Free Electrons:
Such electrons which are present in atom, are not bond to the nucleus. They move freely in the atom. Free electrons mostly occur in metals. They are loosely attached to the nucleus ,thus free to move form one point to other point on application of small energy. Free electrons contributed to the conduction of electricity and heat in metals. They need little energy to move in one direction.
Electrons Movement:
Electrons move form negative terminal toward positive terminal of a conductor. Non metals are bad conductor of heat and electricity because, they lack free electrons which actually contribute to the conduction of electricity. Therefore, non metals acts as insulator.
| Ions | Radicals |
|---|---|
| An ion can carry positive or negative charge | Un paired electrons in the outermost shell |
| It is an atom which behaves like a unit. | Radicals can be neutral, as well as positive or negatively charged |
| They are present in form of pair, having even number. | Nitrogen atom and hydroxyl are best examples of radical. |
| There are simple ions as well as compound ions present in the nature. | Fission of water molecules, lead to the formation of hydroxyl radical |
| Simple ions are monoatomic and compound ions are diatomic or polyatomic. | In case of water, homolytic and heterolytic fission reactions leads to the formation free radicals. |
Frequently Asked Questions:
1. What is the importance of octet rule?
It is a rule which help the chemists to configurate the electrons into shells and sub shells. When we follow this rule it really become easy for us, to deal electronic configuration.
2. What kind of force is present between ionic bond?
Electrostatic force of attraction is present between the atoms in ionic bond. Negative and positive charges are held by the opposite electrostatic force of attraction.
3. Can an atom loss its valence electrons?
An atom has capability to loss its valence electrons to form chemicals bonds. The nature of the bond would be different and vary from element to element.
- What is the location of Valence of electron?
As the name suggests, you will find the electron in the valence shell of an atom. Valence shell is the outer most shell of an atom.
5. What is the valency of Potassium?
Potassium is the element of group two. You will find two electrons in the last shell of potassium. It means that it has ability to loss two electrons. So the valency of potassium is +2.
6. Why noble gases are inert?
The nobles gases not react with any element. Because, they are most stable elements in the nature. Elements react to become stable, if an element is already stable, then it remain non reactive.
7. Do noble gases exist alone in nature?
Yes, they are capable to exist alone in nature without forming compounds. They don’t need any other element to stabilize them. Therefore noble gases avoid reactions.
8. What is ionization energy?
It is the Minimum amount of energy which an atom need to remove the outer most electron(s) which are very loosely bond to the nucleus.
9. What is meant by electronegativity?
It is ability of an atom to to attract other electrons from other atoms toward it self. This property, of an atom play a vital role in the success of various chemical reaction.
10. What is the meaning of atomic size?
Atomic size is the measurement of distance between the nucleus and outer most shell of an atom. From top to bottom in a periodic table, the number of shells increase, thus atomic size of that atom starts increasing.
Conclusion:
We cannot deny the importance of valence electrons in the stability of an atom. Valence electrons are present in the last shell of an atom which is called valence shell. Some shells have capability to accommodate 2 electrons while other valence shells, have ability to acquire 8 electrons. The difference in the number of electrons among different atoms lead to the formation of chemical bonds. Some chemical bonds are ionic in nature while others are covalent in nature. Complete transfer of electrons from one atom to other atom, lead to formation of ionic compounds. While the mutual sharing of electrons lead to the formation of covalent bonds. Covalent bonds are weak as compared to ionic bond and are also not good conductor of electricity. Free electrons are present in high concentration in metals making the conduction of current easy and efficient.