How many valence electrons does Ca have?
Solution:
Ca has two valence electrons.
To find out the number of valence electrons in a Ca atom,we need to look at the periodic table.
The position of Ca in the periodic table is in group IIA.For main group elements,valence electrons are equal to the group number.So,Ca atom has two valence electrons in its valence shell or outermost energy level.
Ca is an element of group 2.Now just consider the unit place digit from group number.You are getting 2 which is equal to the number of valence electrons in Ca.
Here is the another way to find out the valence electrons of Ca.
The symbol of calcium is Ca and the atomic number of potassium is 20.So,it has twenty electrons totally.
Now do the electronic configuration of calcium.
Ca(20) =1s2 2s2 2p6 3s2 3p6 4s2
=[Ar] 4s2
The valence shell is the outermost shell and the electrons that are present in valence shell is called valence electrons.
The valence shell or energy level can be identified by the highest value of principal quantum number ,n.Here the highest value of n is 4.So,the valence shell is the 4th shell or energy level.
In 4th shell ,we get two valence electrons.So each Ca has two valence electrons.
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