Question

Which of the following is the atomic number of a metal?
A.32
B.34
C.36
D.38

Answer 1

Hint:To solve this question, you must first understand the positioning of the different types of elements in the periodic table. The zones for metals, non – metals and metalloids are defined in the periodic table in accordance to their atomic numbers.

Complete step by step solution:
Before we move forward with the solution of this question, let us understand some basic important concepts.
The general definition of a metal that we have been taught from the lower classes is that it is a substance with high electric and thermal conductivity, which is also malleable and ductile in nature. But these are just properties. The proper definition of a metal can be given as a substance which releases electrons for its valence shell when potential is applied across it. This can happen only if the valence is filled in less than half its capacity.
In the periodic table, the elements are arranged on the basis of their atomic numbers. As we move from left to right in a period, the atomic number goes on increasing. Since the atomic number also represents the number of electrons in an atom, we can deduce that the number of electrons keep on increasing in the same valence shell as we move from left to right in a period. This means that elements of the left side of the periodic table have more metallic properties as compared to elements on the right side of the table.
Since metals are considered to have electrical conductivity, then the flow of electrons must also be high in metals. Hence, metals are those elements which have free electrons that help in the conduction of electricity. Also, chemically speaking, metals are those chemical species which always tend to donate electrons in a chemical reaction. These two points can be concluded as metals should have their valence orbitals filled at less than half its capacity. Elements which have 1, 2 or 3 electrons in their valence shell are metals. The electronic configurations of the atomic numbers given to us can be written as:
32: \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^2}\] ; no. of electrons in valence shell = 2+2 = 4
34: \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^4}\] ; no. of electrons in valence shell = 2+4 = 6
36: \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}\] ; no. of electrons in valence shell = 2+6 = 8
38: \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^{10}}4{p^6}5{s^2}\] ; no. of electrons in valence shell = 2+0 = 2
Hence, an element with atomic number 38 has 2 electrons in its valence orbital, and hence it is a metal.

Hence, Option D is the correct option.

Note:
Specific zones for elements showing different metallic characteristics have been marked above. All the elements showing non - metallic characteristics are marked with a purple dot, while the elements with characteristics of both metals and non – metals are marked with a blue dot. These elements are known as metalloids. All the other elements are metals. Polonium is the only metal that behaves like a metal, non - metal and a metalloid. It exhibits different properties at different temperatures. It has atomic number 864 and is highly radioactive metal with no isotopes.