Inorganic Chemistry

UNESCO inaugurated the celebration of 2019 as the International Year of the Periodic Table of Chemical Elements to celebrate its completion of 150 years. The year 2019 marks the 150th anniversary of the creation of the periodic table by Russian scientist Dmitry Ivanovich Mendeleev in 1869.

In the periodic table of chemical elements, the electron affinity decreases down the group but increases up for the group and from left to right across periods of a periodic table because the electron added to energy levels becomes closer to the nucleus, thus a stronger attraction between the nucleus and its electrons. An atom gets larger as the number of electronic shells increases. Therefore, the radius of atoms increases as you go down a certain group in the periodic table of elements. However, the size of an atom will decrease as you move from left to right of a certain period. Thus, Assertion (A) is false, while Reason (R) is true.

The ionization energies are dependent upon the atomic radius. Since going from left to right across a period in the periodic table, the atomic radius decreases and the ionization potential increases, while the ionization potential decreases as one moves down a given group.

In a group of elements, from top to bottom, the electron affinity decreases as the atomic weight increases. As one moves trend-wise from left to right across a period in the periodic table, the electronegativity increases due to the stronger attraction that the atoms obtain as the nuclear charge increases.

The usual property of oxides of Group 3 and 4 of the periodic table are basic and acidic. These oxides are amphoteric (able to react both as a base and as an acid).

Hence, option (b) is the correct answer.

The element found the maximum in the soil layer is Oxygen 46.60% followed by Silicon 27.72%, Aluminium 8.13%, Iron 5.00%, and Calcium 3.65%.

The element that is present in the largest amount in terms of percent by mass in the earth's crust is Oxygen.

The most abundant element on earth's surface after Oxygen is Silicon. It was discovered by J.J. Berzelius in 1824. The word 'Silicon' was taken from the Latin word silex. Silicon chips are used as a semiconductor in computers.

The most abundant element in the Universe is Hydrogen, which makes up about 3/4 of all matter. Helium makes up most of the remaining 1/4. Thus, it is clear that Hydrogen is the most common and abundant element in the Universe. While the most abundant element in the earth's crust is Oxygen, making up 46.6% of the earth's crust.