Periodic Classification of Elements Test - 14

The triad was the earliest atomic-weight classification of the elements.Such triads—including chlorine-bromine-iodine, calcium-strontium-barium, and sulfur-selenium-tellurium—were noted by the German chemist J.W. Döbereiner between 1817 and 1829. Dobereiner's triads grouped elements with similar chemical properties. Second element in each triad is about equal to the average of the atomic weights of the first and third elements. Atomic  weight of strontium fell midway between the weights of calcium and barium.

Hence the correct answer is option (D).

In the periodic table, down the group number of valence electron remains constant that is why they show similar chemical properties.

Hence, the correct answer is option (D).

The correct form of Zinc oxide will be ZnO. As both have the same valency i.e two.

Hence the correct answer is option (C).

In group 13 B is a non-metal and other elements of group 13 are metals i.e. Al, Ga, In, Tl.

Hence the correct answer is option (D).

Metals Period - reactivity decreases as you go from left to right across a period.

Non-metals Period - reactivity increases as you go from the left to the right across a  period. 

Hence the correct answer is option (D).

The atom attains stable electronic configuration either by gaining or losing electrons. In this process the outermost shell (which is of high energy) and electrons of outermost shell are involved.

Hence the correct answer is option (B).

In the year 1864, the British chemist John Newlands attempted the 56 elements known at that time. He arranged them in an ascending order based on their atomic masses and observed that every 8th element had similar properties. He started with hydrogen and ended with thorium (atomic weight 232), into eight groups, which he likened to octaves of music.

Hence the correct answer is option (B).

Although H is present in the first group of modern periodic table i.e. of metals but H resembles non-metals property too.

So, H is a non-metal.

Hence the correct answer is option (A).

Cu, Ag and Au are known as coinage metals. 

Hence the correct answer is option (D).

Elements of atomic number from 58 to 71 are known as inner transition elements (Lanthanoid elements) as well as rare earth metals.

Hence the correct answer is option (B).

Electropositivity of elements decrease across a period because the atomic size decreases and electronegativity increases.

Hence the correct answer is option (A).

According to the Bohr’s theory the electronic configuration will be 2,8,18 and so on. From electronic configuration it is clear that third orbit can accommodate  maximum 18 electrons.

Hence the correct answer is option (A).

The natural element with the highest metallic character is Cesium, which is found directly above Francium on the periodic table.

Hence the correct answer is option (C).

Group 18 elements are knowns as inert gases. They have stable electronic configuration due to complete octet.

Hence the correct answer is option (B).

Since in an atom, the number of protons are equal to the atomic number of that atom. In sodium, the number of protons will be 11 because its atomic number is also 11.

Hence the correct answer is option (C).