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Answers
Answer:
1) Did Dobereiner's triads also exist in the column of Newland's Octaves?Compare and find out.
ANS- Only one triad of Dobereiner's triad exists in the column of Newland's Octaves. The triad formed by the elements Na,Li and K of Dobereiner's triads also occurred in columns of Newland's Octaves.
2) What were limitations of Dobereiner's classification?
Besides Gallium which other elements have been discovered that were left by Mendeleef in the table
ANS - Dobereiner could only form triads of the elements he knew at that time and the elements available.
Germanium and Scandanium.
3) what was criteria used by Mendeleef in the periodic table?
ANS-Mendeleef used atomic masses of the elements as the criteria for creating his periodic table. In this table, the elements were arranged increasing order of their atomic masses.
4) why do u think noble gases are placed in a separate group?
ANS-Nobel gases are placed in a separate group because they are extremely unreactive & they generally do not combine with other elements of the periodic table.
5) How could modern periodic table remove anomalies of Mendeleef periodic table?
ANS-The Modern Periodic Table could remove various anomalies of Mendeleev's Periodic Table:
a) In the Modern Periodic table elements are arranged in the increasing order of their atomic number, removing the anomaly regarding certain pairs of elements in Mendeleev's periodic table
b) Atomic no. of cobalt is 27 and nickel is 28. Hence cobalt will come before nickel even though its atomic mass is greater.
c) All isotopes of the same elements have different atomic masses, but same atomic number; therefore they are placed in the same position in the modern periodic table.
6) Name 2 elements u would expect to show similar chemical reactivity to Mg. What is the basis for ur choice?
ANS-Calcium (Ca) and strontiun (Sr) are expected to shows chemical reaction similar to magnesium (Mg). This is because the number of valence electron(2) is same in all these three elements and since chemical properties are due to valence electrons, they show same chemical reactions.
Name
a) the elements that have single e- in outermost shell
ANS- hydrogen, lithium, sodium, potassium, Rubidium, cesium and francium elements have one electron in their outermost shell.
b) two elements that have 2 e- in outermost shell.
ANS- The elements Be, Mg and Ca each having two electrons in their outermost shells are in periods 2, 3, and 4 respectively of the modern periodic table.
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