What were the criteria used by Mendeleev in creating his Periodic Table?
Mendeleev concentrated on various compounds formed by the elements with Hydrogen and Oxygen. Among physical properties, he observed the relationship between the atomic masses of various elements while creating his periodic table
Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (Any two)
Germanium and Scandium are the element that are left by Mendeleev in his Periodic Table since its discovery.
Use Mendeleev’s Periodic Table to predict the formulae for the oxides of the following elements: K, C, AI, Si, Ba
K- K2O
C-C2O4 or CO2
Al- Al2O3
Si-Si2O4 or SiO2
Ba2O2 or BaO
Oxygen is a member of group VI A in Mendeleev’s periodic table. Its valency is 2. Similarly, the valencies of all the elements listed can be predicted from their respective groups. This will help in writing the formulae of their oxides.
(i) Potassium (K) is a member of group IA. Its valency is 1. Therefore, the formula of it is K2O.
(ii) Carbon (C) is a member of group IV A. Its valency is 4. Therefore, the formula of it is C2O4 or CO2.
(iii) Aluminium (Al) belongs to groups III A and its valency is 3. The formula of its oxide is Al2O3.
(iv) Silicon (Si) is present in group IV A after carbon. Its valency is also 4. The formula oxide is Si2O4 or SiO2.
(v) Barium (Ba) belongs to group II A and the valency of the element is 2. The formula of oxide of the element is Ba2O2 or BaO.
What were the limitations of Newlands’ Law of Octaves?
Limitations of Newlands’ Law of Octaves are as follows
What were the limitations of Döbereiner’s classification?
(i) They were not applicable for very low mass or very high mass elements.
(ii) All the elements couldn’t fit into Dobereiner’s triads.
(iii) As the methods to calculate atomic mass improved, Dobereiner’s triads validity began to decrease. For example, in the triad of F, Cl and Br, the arithmetic mean of atomic masses of F and Br are not equal to the atomic mass of CI
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
Döbereiner’s triads did exist in the columns of Newlands’ Octaves; For example, the elements
Lithium (Li), Potassium (K) and Sodium (Na) constitute a Dobereiner’s Triad but are also found in the second column of Newland’s Octaves.
Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
| Mendeleev’s Periodic Table | Modern Periodic Table |
| Elements are arranged in the increasing order of their atomic masses. | Elements are arranged in the increasing order of their atomic numbers. |
| There are 8 groups | There are 18 groups |
| Each groups are subdivided into sub group ‘a’ and ‘b’ | Groups are not subdivided into sub-groups. |
| Groups for Noble gas was not present as noble gases were not discovered by that time | A separate group is meant for noble gases. |
| There was no place for isotopes. | This problem has been rectified as slots are determined according to atomic number |
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
Calcium has an atomic number of 20, and thus has an electronic configuration of 2, 8, 8, 2. Thus, calcium has 2 valence electrons. The electronic configuration of the element having atomic number 12 is 2, 8.2. Thus, this element with 2 valence electrons resemble calcium the most
How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
The number of valence electrons decides an atom’s position in the periodic table while the electronic configuration decides the number of valence electrons.
Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why
Atomic number of Nitrogen is 7 hence Electronic configuration of Nitrogen is 1s2 2s2 2p3
Atomic number of Nitrogen is 15 hence Electronic configuration of Phosphorous is 1s2 2s2 2p6 3s2 3p3
On moving down a group in the periodic table, the number of shell increases. Due to this, valence electrons move away from the electrons and the effective nuclear charge decreases. This causes the decrease in the tendency to attract electron and hence electro negativity decreases. Because of all these reasons Nitrogen is more electronegative than phosphorus
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