Consider the section of the periodic table:

Identify A, B, C and D.

A teacher of Xth class, during teaching explains the importance of the music in our daily life. She was telling to her students that in the Indian system of music, there are seven musical notes in a scale sa, re, ga, ma, pa, da, ni. And in the west notations used are do, re, mi, fa, so, la, ti. The notes in a scale are separated by whole frequency intervals of tones. Every eighth note is similar to the first one and it is first note of next scale. A musician use these notes for composing music of a song.

Read the above passage carefully and answer the following questions accordingly.

(i) Is the situation discussed above is similar to something in chemistry? Explain.

(ii) What are the limitations of the above principle in case of chemistry?

(iii) What are the values you will infer from above passage?

Every school has assembly Students stand in rows which should be straight, horizontally as well vertical. Each class stands in a single line, with schools. Each class has a name, e.g. class 1, 2, 3... etc. In general, height of students of class 1st is smallest and 12th is biggest. Everyone sings the prayer at the same time.

Read the above passage carefully and answer the following questions given below.

(i) Do you find similarity between rows of assembly with periodic table? Explain two points.

(ii) How can you compare qualities of students with elements of periodic table?

(iii) What values are inculcated during assembly of school?

The correct order of increasing acidic nature of SO₂, SiO₂ <P₂O₃ and Al₂O₃ is

An element X combines with hydrogen to form a compound XH₃. The element Xis placed on the right side of the periodic table. Which of the following statement is correct for element X?

I. Has two valence electrons.

II. Is a metal and is solid.

III. Is a non-metal and is a gas.

IV. Has five valence electrons.

V. XH₃ reacts with water to forma basic compound.