Elements NDA Questions

NDA Chemistry

Elements MCQ Questions


1.
Dobereiner's Law of Triads (1829) states that the atomic mass of the middle element of a triad is approximately equal to:
A.
The arithmetic mean of the atomic masses of the first and third element
B.
The harmonic mean of atomic masses of first and third elements
C.
The geometric mean of atomic masses of first and third elements
D.
The product of atomic masses of first and third elements
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ANSWER :
A. The arithmetic mean of the atomic masses of the first and third element
2.
Which of the following is a correct example of Dobereiner's Triad?
A.
Fe (56), Co (58.9), Ni (58.7)
B.
C (12), N (14), O (16)
C.
Li (6.9), Na (23), K (39.1) — mean of 6.9 and 39.1 ≈ 23
D.
H (1), He (4), Li (6.9)
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ANSWER :
C. Li (6.9), Na (23), K (39.1) — mean of 6.9 and 39.1 ≈ 23
3.
John Newlands proposed the 'Law of Octaves' in 1865. According to this law:
A.
Properties repeat every six elements
B.
Every eighth element has properties similar to the first element, when arranged in order of increasing atomic mass
C.
Every element forms octets in bonding
D.
Every seventh element repeats its properties
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ANSWER :
B. Every eighth element has properties similar to the first element, when arranged in order of increasing atomic mass
4.
The main drawback of Newlands' Law of Octaves was:
A.
It arranged elements in decreasing order of atomic mass
B.
It grouped metals and non-metals together without distinction
C.
It worked only for lighter elements up to calcium and failed for heavier elements; also, no provision was made for undiscovered elements
D.
It did not consider isotopes of any element
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ANSWER :
C. It worked only for lighter elements up to calcium and failed for heavier elements; also, no provision was made for undiscovered elements
5.
Mendeleev's Periodic Law (1869) states that the properties of elements are a periodic function of their:
A.
Number of neutrons
B.
Electronic configuration
C.
Atomic numbers
D.
Atomic masses
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ANSWER :
D. Atomic masses
6.
Mendeleev left gaps in his periodic table for undiscovered elements and predicted their properties. The element that was later discovered filling the gap below silicon was named:
A.
Technetium (Tc)
B.
Scandium (Sc)
C.
Germanium (Ge), which Mendeleev called 'Eka-silicon'
D.
Gallium (Ga)
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ANSWER :
C. Germanium (Ge), which Mendeleev called 'Eka-silicon'