2. If the two members of a Dobereiner triad are phoshorus and antimony,the third member of this triad is --
3. The most significant contribution towards the development of periodic table was made by
4. The number of elements known at present is ____.
The number of elements known at present is 114. In 1800, only 31 elements were known. By 1865, the number of identified elements had more than doubled to 63. At present 114 elements are known. Of them, the recently discovered elements are man-made. Efforts to synthesis new elements are continuing.
5. Law of Triads was referred to as ____ relationship.
Law of Triads was referred to as Dobereiner's relationship. The German chemist, Johann Dobereiner was the first to consider the idea of trends among properties of elements. By 1829, he noted a similarity among the physical and chemical properties of several groups of three elements (Triads). In each case, he noticed that the middle element of each of the Triads had an atomic weight about half way between the atomic weights of the other two. Also, the properties of the middle element were in between those of the other two members. This Law of Triads seemed to work only for a few elements. It was dismissed as coincidence.
6. The statement that is not correct for the periodic classification of element is
7. The statement that is not correct for periodic classification of elements is-
8. Which of the following sets has strongest tendency to form anions?
N,O and F(p-block elements) are highly electronegative non metals andwill have the strongest tendency to form anions by gaining electrons from metal atoms.
9. French geologist A.E.B.de Chancourtois arranged the then known elements in order of ____ and made a ____ table of elements to display the periodic recurrence of properties.
"French geologist A.E.B.de Chancourtois arranged the then known elements in order of increasing atomic weights, and made a cylindrical table of elements to display the periodic recurrence of properties.This classification did not attract much attention. "
10. The periodic law owes its development to the Russian chemist ____ and the German chemist ____.
The periodic law owes its development to the Russian chemist Dmitri Mendeleev and the German chemist Lothar Meyer. Johann Dobereiner was the first to consider the idea of trends among properties of elements. John Alexander Newlands propounded the Law of Octaves.
11. According to the periodic Law of elements, the variation in properties of elements is related to their
The properties of elements change with a change in atomic number.
12. Mendeleev classified elements in--
13. Noble gases were included in Mendeleev's periodic table in the --
14. In the modern periodic table one of the following does not have appropriate positions-
15. The screening effect of 'd' electrons is
The screening effects follows the order s > p >d > f >
16. Pauling 's electronegativity values for elements are useful in prediciting
(a) Pauling scale of electronegativity was helpful in predicting. (i) Nature of bond between two atoms. (ii) Stability of bond. by calculating the difference in electronagativities polarity of bond can be calculated.
17. In the periodic table, with the increase in atomic number, the metallic character of an element
18. The old periodic law states that the properties of the elements are a periodic function of their ____.
"The periodic law states that the properties of the elements are a periodic function of their atomic weights.Mendeleev was responsible for publishing the Periodic Law for the first time. "
19. Mendeleev's predictions for the elements Eka-aluminium and Eka-silicon were discovered later as ____ and ____ respectively.
"Mendeleev's predictions for the elements Eka-aluminium and Eka-silicon were discovered later as gallium and germanium. Mendeleev predicted not only the existence of gallium and germanium, but also described some of their general physical properties. "
20. Pick out the correct statement regarding Law of Octaves.
"The correct statement is, 'Newlands's Law of Octaves seemed to be true only for elements up to calcium.' The correct statement for the other options are, * Option A - John Alexander Newlands propounded the Law of Octaves, in 1855. * Option B - He arranged the elements in increasing order of their atomic weights and noted that every eighth element had properties similar to the first element. * Option D - As per the Law of Octaves Be, Mg and K show resemblance in properties "
21. In the periodic table from left to right in a period the atomic volume.
Atomic volume is the volume occupied by the one gram of an element. Within a period from left to right, atomic volume first decreases and then increaes due to increaes of nuclear charge and increase in the number of electrons in the valence shell.
22. The atoms of elements belonging to the same group of periodic table have the same--
23. The elements with atomic numbers 2, 10, 18, 36, 54 and 86 are all-
24. The number of elements in each of the inner transition series is --
25. Pick out the correct statement regarding Mendeleev's periodic table.
"The correct statement is, 'Mendeleev predicted the existence of Eka-Aluminium and Eka-Silicon. The right statement of the other options are, Option A - Mendeleev relied on the similarities on the empirical formulas and properties of the compound formed by the elements.' * Option B - Some of the elements do not fit the classification with increasing atomic weight. * Option C - The elements in a group are similar in their properties"
26. The atomic mass of Sr as predicted according to the Dobereiner's law of traids in the triad Ca(Z=40), Sr, Ba(Z=137)is ____.
"According to the Dobereiner's law of traids, the atomic mass of the middle element in the triad is the average of the atomic masses of 1st & the 3rd elements. 40+1372/2= 88 amp."
27. The noble gases are unreactive because
28. Which of the following element is not in the liquid state?
29. The electron affinity for the inert gases is --
30. Which is metalloid--
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