The atom of an element has electronic configuration 2, 8,8, 2.
(a) What is the atomic number of the element?
(b) To which of the following elements would it be chemically similar? (Atomic numbers of elements are given in brackets):
He (2); O (8); Mg (12); K (19) Give reason for your choice.
(a) Electronic Configuration (2, 8, 8, 2) hence, the Atomic Number is 2 + 8 + 8 + 2 = 20. Calcium has atomic number 20, hence the given element is calcium.
(b) In the outermost shell of Calcium there are 2 electrons (2,8,8,2).
The outermost shell of Helium, He has 2 electrons.
The outermost shell of Oxygen, O has 6 electrons (2,6).
The outermost shell of Magnesium, Mg has 2 electrons (2,8,2).
The outermost shell of Potassium, K has 1 electron (2,8,8,1).
Out of these 4 elements, only Magnesium has + 2 valency as Calcium, so it shows the same properties as calcium as both are alkaline earth metals.
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