Assertion: One atomic mass unit is defined as one-twelfth of the mass of one carbon-12 atom.Reason: Carbon-12 isotope is the most abundant isotope of carbon and has been chosen as the standard.A.Both Assertion and Reason are true and Reason is the correct explanation of Assertion.B.Both Assertion and Reason true but Reason is not the correct explanation of Assertion.C.The assertion is true but Reason is false.D.Both Assertion and Reason are false.

Which of the following is likely to be least stable?

• (A) Ca₄₀
• (B) Mn₅₅
• (C) Sn₁₁₉
• (D) Al₃₀

Which of the following is not a Lewis acid?

• A. BF₃
• B. AlCl₃
• C. FeCl₃
• D. PH₃

Which of the following is not a property of compounds?

• (A) They are made up of two or more kinds of atoms.
• (B) They cannot be broken down into two or more simpler substances by physical means but by chemical means only.
• (C) Properties of compounds differ from those of their elements.
• (D) None of the above.

Which of the following is polar?

• A. NF₃
• B. BF₃
• C. SF₄
• D. SiF₄

Which of the following metals exists in their native state in nature?

• (i) Ca
• (ii) Au
• (iii) Zn
• (iv) Ag

A. (i) and (ii)

B. (ii) and (iii)

C. (ii) and (iv)

D. (iii) and (iv)