Carbon, a chemical element with the symbol C and atomic number 6, is a non-metallic element with different appearance means graphite has a black, metallic appearance while diamond has a clear appearance. Carbon has three naturally occurring isotopes: 12C & 13C (stable), and 14C (radioactive).
Carbon is the
fourth most abundant element in the universe after hydrogen, helium, and
oxygen. Mostly it is found in the form of organic compounds, and with combine
with air in the form of carbon dioxide (CO2). The carbon atoms can bond together
in diverse forms which result in the formation of different allotropes. Graphite, diamond,
and buckminsterfullerene are the best-known allotropes of carbon.
You are here to
know valence electrons of carbon atom, aren’t you? Don’t worry along with carbon
valence electrons we will explain its valency also. But before that let’s have
some basic ideas about what these two terms are:
Difference Between Valence Electrons and Valency
Valence electrons
are the total number of electrons present in the outermost shell of an atom
(i.e. in outermost orbital). The valence electrons for a neutral atom is always
definite, it cannot be varied (more or less) in any condition for a particular
atom and may or may not be equal to its valency.
Valency is defined
as the total number of electrons an atom can lose, gain, or share at the time
of bond formation to get a stable electronic configuration i.e. to complete an
octet. The valency of an atom can be variable in different compounds or chemical
reactions due to the different bonding circumstances. Most of the time valency
varies/changes due to change in oxidation and reduction states.
Carbon (C) Valence Electrons
There are four
simple steps to find out the valence electrons for carbon atom which are:
Step 1: Find the
Atomic Number
To find out the
atomic number of carbon, we can use the periodic table. With the help of the
periodic table, we can easily see that the atomic number of carbon is 6. As its
atomic number is 6, it has six protons, and for neutral carbon, the number of
protons are always equal to the number of electrons i.e. has six electrons in
its nucleus.
Step 2: Write
Electron Configuration
Electron
configuration is the arrangement of electrons on the orbitals. The carbon atom
has a total of five electrons so, we have to put 6 electrons in orbitals. The electrons
will be placed in different orbitals according to the energy level: [1s, 2s,
2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f]. Now,
Carbon electron configuration C (6) = 1s2 2s2 2p2 (complete configuration).
= [He] 2s22p2 (condensed configuration).
Step3: Determine
Valence Shell
As we know, the valence shell of an atom can be found from the highest number of principle quantum numbers which are expressed in the term of n, and in [He] 2s22p2, the highest value of n is 2 so that the valence shell of B is 2s22p2.
Step 4: Find
Valence Electrons
The total number of electrons present in the valence shell of an atom are called valence electrons, and there are a total of four electrons present in the valence shell of carbon (2s22p2). Thus, carbon has four valence electrons.
Valency of Carbon (C)
There are many
different ways to find out the valency of an atom which reflects the ability of
an atom to bond with other atoms. Valence describes how easily an atom or a
free radical can combine with other chemical species. The valency of an atom is
determined based on the number of electrons lost, gained, or shared with
another atom at the time of bond formation.
An atom is said to
be stable when its outermost shells have eight electrons (except H & He).
If the total number of electrons in outermost shells is between one to four,
the atom has positive valency and if electrons are between four to eight, the
valency is calculated by subtracting from eight and valency will be zero. Atoms
having four outermost electrons possess both positive and negative valency, and
atoms having eight outermost electrons, valency will be zero (i.e. noble
gases).
Elements like carbon
can reach the stable state (nearest inert gas configuration) either by losing 4
outermost electrons or by getting 4 electrons. So that the valency of carbon
is 4 (tetravalency).
Note: Carbon has
both +4 & -4 valency/oxidation states. If it loses three electrons to reach a stable
state (i.e. He), its valency will be +4. But if it gains five electrons to
reach a stable state (i.e. Ne), its valency will be -4 as explained above. For example in CO2, the oxidation state of carbon is +4 while in CH4, the oxidation state is -4.
In another sense, a
carbon atom can form four covalent bonds in chemical bonding (For example CH4,
CCl4, etc.), and that what valency is, the maximum ability to form bonds with
different atoms at the time of chemical reactions.
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