Periodic Classification of Elements Test - 1

Pobereiner selected his triads purely on the basis of similarity in properties.

When arranged in the increasing order of atomic masses, magnesium is the eighth element after beryllium; and thus, the two elements have similar properties.

All of the earlier attempts at classification were based on the assumption that atomic mass of the elements is the fundamental property that decides the chemical behaviour of the elements; until Moseley pointed out that the atomic number of the elements is a more basic property.

Though Mendeleev gave the periodic law, which states that the properties of elements are periodic functions of their atomic masses, he gave priority to the similarity in the formulae of oxides and hydrides. He proposed that the elements with similar formulae of oxides and hydrides will show resemblance in all their properties.

Electron affinity of an element is the tendency to gain an electron and form an anion.
Electron affinity increases across the period and decreases down the group.

Even though fluorine is more electronegative than chlorine, the latter has a greater electron affinity and can form anions more readily as being bigger in size it can adjust the incoming electron more easily.

In case of fluorine, repulsions come into play owing to its small size.

Ionisation of an atom is an endothermic process, as energy is used to overcome the nuclear pull on the atom.

Z = 10
Electronic configuration: 2,8
The element is Neon.

Since, there are two shells filled, it belongs to the period II.

As there are eight valence electrons, the group number is 8 + 10 = 18.

Scandium is the present day element that was named Eka Boron, and Mendeleev not only predicted its existence, but also its position in his periodic table.

Mendeleev grouped together the elements having similar formulae of oxides and hydrides. The general formulae of oxides and hydrides of all elements of the carbon group are RO₂ and RH₄, respectively.

For example: CO₂, SiO₂

CH₄, SiH₄