Classification of periodic elements 2 Flashcards
What is the basic theme of organisation in the periodic table?
The basic theme of organisation of elements in the periodic table is to simplify and systematize the study of the numerous properties of all the elements and their compounds. This has been done by arranging the elements in such a way that similar elements are placed together while dissimilar elements are separated from one another. This has made the study simple to remember because the properties of the elements are now studied in the form of groups or families having similar properties rather than studying the elements individually.
Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that?
Mendeleev used atomic weight as the important property for the classification of elements. Mendeleev arranged all the known elements in the form of a table known as periodic table. He observed that some of the elements did not fit in very will with his scheme of classification if the order of atomic weight was strictly followed. He showed courage to ignore the order of atomic weights thinking that the atomic weight measurements might be incorrect.
What is the basic difference in approach between the Mendeleev’s periodic law and the Modern periodic law?
According to Mendeleev’s periodic law, the physical and chemical properties of the elements are periodic function of their atomic weight. On the other hand, according to modern periodic law, the properties are periodic function of their atomic numbers.
How would you react to the statement that electronegativity of N on Pauling scale is 3.0 in all its compounds?
The electronegativity of nitrogen will not be 3.0 in all its compounds. It depends upon the other atoms attached to it. It also depends on the state of hybridisation and the oxidation state of the element.
Would you expect the first ionization enthalpies for two isotopes of the same element to be the same or different? Justify your answer.
Isotopes are atoms of the same element which have same atomic number but different mass number. Therefore, they have same number of electrons and nuclear charge (protons). Thus, they will have almost same first ionization enthalpies.
Write the general electronic configuration of s, p, d and f block elements.
s-block: ns1-2
p-block: ns2np1-6
d-block (n-1) d1-10 ns0-2
f-block (n-2)f1-14
(n-1) d0-1 ns2
All transition elements are d-block elements,
but all d-block elements are not transition
elements. Explain.
All the elements in between s-and p-block i.e., between
group 2 and 13 are called transition elements.
Elements in which the last electron enters the d-orbitals of their respective penultimate shells are called d-block elements. According to this definition, Zn, Cd and Hg cannot be regarded as d-block elements because last electron in these elements enters the s-orbital of their outermost shells rather than d-orbital of their penultimate shells. Therefore, these elements should not be regarded as d-block elements. However, the properties of these elements resemble with d-block elements. Therefore, to make the study of periodic classification of elements more rational, these are studied alongwith d-block elements. Thus, on the basis of properties, all the transition elements are d-block elements but on the basis of electronic configuration, all d-block elements are not transition elements.
Justify the given statement with suitable examples “the properties of the elements are a periodic function of their atomic numbers.”
The similarities in the properties arise due to the same distribution of electrons in the outermost orbitals or electronic configuration which depends upon the atomic number. The elements present in a group or period exhibit similar chemical properties which depend upon the atomic number.
Most electronegative element
F
Highest -ve E.G.E
Cl
____has+ve E.G.E
noble gases
Size decreases with increase in n.c
isoelectronic species
__have high IE
noble gases
smallest element in 2nd period
F
largest element in 2nd period
Li
