Calcium, a chemical element with the symbol Ca and atomic number 20, is a reactive metal that can form a dark oxide-nitrite layer when exposed to the atmosphere. It is the third most abundant metal on the earth's surface after iron and aluminum.
The most common
compounds of calcium are calcium carbonate which is found in the form of limestone. It is a very essential element for human beings because it plays a vital role
in muscular health, digestive system, blood circulation, and building of bonds.
You are here to
know valence electrons of calcium atom, aren’t you? Don’t worry along with calcium
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 are 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.
Calcium (Ca) Valence Electrons
There are four simple
steps to find out the valence electrons for calcium atom which are:
Step 1: Find the
Atomic Number
To find out the
atomic number of calcium, we can use the periodic table. With the help of the
periodic table, we can easily see that the atomic number of calcium is 20. As
its atomic number is 20, it has 20 protons, and for neutral calcium, the number
of protons is always equal to the number of electrons i.e. has 20 electrons in
its nucleus.
Step 2: Write
Electron Configuration
Electron
configuration is the arrangement of electrons on the orbitals. The calcium atom
has a total of 20 electrons so, we have to put 20 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,
Calcium electron configuration Ca (20) = 1s22s22p63s23p64s2 (complete configuration).
= [Ar] 4s² (condensed configuration).
Step 3: 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 [Ar]4s², the highest value of n is 4 so that the valence shell of calcium is 4s².
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 two electrons present in the valence shell of calcium (4s²). Thus, calcium has two valence electrons.
Also Read:
- Valence Electrons & Valency of Magnesium (Mg).
- Valence Electrons & Valency of Boron (B).
- Valence Electrons & Valency of Nitrogen (N).
Valency of Calcium (Ca)
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 calcium
can reach the stable state (nearest inert gas configuration: Ar) by losing two
electrons. So that the valency of calcium is 2.
Note: Usually, calcium
has a stable oxidation state of +2 most of the time but it may differ in
some compounds. Do not confuse with +2 or something else (+1, -2, etc.) with
positive or negative sign, it is just an oxidation number that can vary from compound to compound. But its valency is always 2 in any case.
In another sense, a
calcium atom can form a maximum of two covalent bonds in a chemical bonding (For example:
CaO, CaCl2, CaSO4, etc.), and that what valency is, the maximum ability to form
bonds with atoms at the time of chemical bonding.
We can also find
the valency of calcium with the help of the periodic table. As calcium belongs
to group 2A (or IIA) along with beryllium (Be), magnesium (Mg), strontium (Sr),
barium (Ba), and radium (Ra). These group elements are also called alkaline
earth metals. All these elements have valency two.
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