Answer : The correct option is, Magnesium because it is a group 2 element with two valence electrons.
Explanation :
Atomic number = 20
Electronic configuration of Ca =
Number of valence electrons in Ca = 2
The number of inner shell electrons in Ca = 18
This option is wrong because lewis-dot structure shows only valence electrons not inner shell electrons.
Atomic number = 6
Electronic configuration of C =
Number of valence electrons in C = 4
This option is wrong because only outermost p-sublevel electrons are not showing in lewis-dot structure.
Atomic number = 3
Electronic configuration of Li =
Number of valence electrons in Li = 1
This option is wrong because it has only 1 electron in outermost shell.
Atomic number = 12
Electronic configuration of Ma =
Number of valence electrons in Ma = 2
This option is correct.
Lewis-dot structure : It is defined as the structure in which valence electrons of the atom is shown as dots.
The lewis-dot structure of these elements are shown below.