In what manner is the long form of periodic table better than Mendeleev's
periodic table? Explain with examples.
Superiority of the Long form of the Table over Mendeleev's Table:
(i) This table is based on a more fundamental property, i.e., atomic number.
(ii) It correlates the position of the elements with their electronic configurations more clearly.
(iii) The completion of each period is more logical. In a period as the atomic number increases, the energy shells are gradually filled up until an inert gas configuration is reached. It eliminates the even and odd series of IV, V, VI and VII periods of Mendeleev's periodic table.
(iv) The position of VIIIth group is appropriate in this table. All the transition elements have been brought in the middle as the properties of transition elements are intermediate between s- and p-block elements.
(v) Due to separation of two subgroups, dissimilar elements do not fall together. One vertical column accommodates elements with same electronic configuration thereby showing same properties.
(vi) In this table, a complete separation between metals and non-metals has been achieved. The non-metals are present in the upper right comer of the periodic table.
(vii) There is a gradual change in properties of the elements with increase in their atomic numbers, i.e., periodicity of properties can be easily visualized. The same properties o recurrence in properties occur after the intervals of 2, 8, 8, 18, 18 and 32 elements which indicates the capacity of various periods of the table.
(viii) This arrangement of elements is easy to remember and reproduce.
Give reasons:
(i) IE1 of sodium is lower than that of magnesium whereas IE2 of sodium is higher than that of magnesium.
(ii) Noble gases have positive value of electron gain enthalpy.
All transition elements are d-block elements, but all d-block elements are not transition elements. Explain.
(a) How does atomic radius vary in group in the periodic table?
(b) Explain
(i) Radius of cation is less than that of the atom.
(ii) Radius of anion is more than that of the atom.
(iii) In iso-electronic ion, the ionic radii decreases with increase in atomic number.
Among the elements B, Al, C and Si,
(a) which element has the highest first ionization enthalpy
(b) which element has the most metallic character?
Justify your answer in each case.
Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionization (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?
(a) 2 (b) 13 (c) 1 (d) 17
Which of the following elements can show covalency greater than 4?
(a) Be (b) P (c) S (d) B
Would you expect the first ionization enthalpies of two isotopes of the same element to be the same or different? Justify your answer.
What is the cause of periodicity in properties of the elements? Explain with two examples.
Name different blocks of elements in the periodic table. Give general electronic configuration of each block.
Discuss the main characteristics of four blocks of elements in the periodic table? Give their general electronic configuration.
Justify the given statement with suitable examples "the properties of the elements are a periodic function of their atomic numbers".
Consider the following species:
N3-, O2-, F–, Na+, Mg2+, Al3+
(a) What is common in them?
(b) Arrange them in order of increasing ionic radii?
Which of the following have no unit?
(a) Electronegativity (b) Electron gain enthalpy
(c) Ionisation enthalpy (d) Metallic character
Arrange the elements N, P, O and S in the order of
(i) increasing first ionisation enthalpy.
(ii) increasing non-metallic character.
Give reason for the arrangement assigned.
Which of the above elements is likely to be:
(a) the least reactive element (b) the most reactive metal
(c) the most reactive non-metal (d) the least reactive non-metal
(e) the metal which can form a stable binary halide of the formula MX2(X = halogen)
(f) the metal which can form a predominantly stable covalent halide of the formula MX (X = halogen)?
Elements A, B, C and D Iwoe atomic numbers 12,19, 29, and 36 respectively. On the basis of electronic configuration, write to which group of the periodic table each element belongs.
The formation of the oxide ion, 02-(g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
O(g) + e–→0– (g), ∆H= -141 kJ mol-1
0–(g) + e–→O2 (g), ∆H = +780 kJ mol-1
Thus process of formation of O2- ion in gas phase is unfavourable even though O2- is isoelectronic with neon. It is due to the fact that
(a) Oxygen is more electronegative.
(b) Addition of electron in oxygen results in larger size of the ion.
(c) Electron repulsion outweighs the stability gained by achieving noble gas configuration.
(d) 0– ion has comparatively smaller size than oxygen atom.
Which element do you think would have been named by
(i)Lawrence Berkeley Laboratory
(ii)Seaborg’s group?
Among the second period elements, the actual ionization enthalpies are in the order: Li
(i) Be has higher ∆iH1than B ?
(ii) O has lower ∆iH1 than N and F?
Which of the following pairs of elements would have a move negative electron gain enthalpy? (i) O or F (ii) F or Cl.
Predict the formulas of the stable binary compounds that would be formed by the combination of the following pairs of elements:
(a) Lithium and oxygen(b) Magnesium and nitrogen
(c) Aluminium and iodine(d) Silicon and oxygen
(e) Phosphorous pentafluoride (f) Element 71 and fluorine.
p-Block elements form acidic, basic and amphoteric oxides. Explain each property by giving two examples and also write the reactions of these oxides with water.
Discuss and compare the trend in ionization enthalpy of the elements of group 1 with those of group 17 elements.
The first ionization enthalpy values (in kJ mol -1) of group 13 elements are:
B Al Ga In Tl
801 577 579 558 589
How would you explain this deviation from the general trend?
What do you understand by ‘Representative elements’? Name the groups whose elements are called representative elements.
Define the term ionization enthalpy? How does it vary along a period and along a group?
Give the electronic configuration of the transition elements. Write their four important characteristics.
Discuss the main features of long form of the periodic table. What are the advantages of long . form of periodic table?
Define electron gain enthalpy. What are its units? Discuss the factors which influence the electron gain enthalpy.
Arrange the following as stated: (i) N2, 02, F2, Cl2(Increasing order of bond dissociation energy) (ii) F, Cl, Br, I (Increasing order of electron gain enthalpy) (iii) F2, N2, Cl2, O2(Increasing order of bond length).
Electronic configurations of four elements A, B, C and D are given below:
(A) 1s2 2s12p6
(B) 1 s2 2s2 2p4
(C) 1s2 2s2 2p6 3s1
(D) Is2 2s2 2p5
Which of the following is the correct order of increasing tendency to gain electron?
(a) A < C < B < D
(b) A < B < C < D
(c) D < B < C < A
(d) D < A< B < C
Which of the following elements will gain one electron more readily in comparison to other elements of their group?
(a) S (g) (b) Na (g) (c) O (g) (d) Cl(g)
Identify the group and valency of the element having atomic number 119. Also predict the outermost electronic configuration and write the general formula of its oxide.
Choose the correct order of atomic radii of fluorine and neon (in pm) out of the options given below and justify your answer.
(i) 72,160 (b) 160,160 (c) 72,72 (d) 160,72
What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.
Electronic configurations of some elements are given in column I and their electron gain enthalpies are given in column II. Match the electronic configuration with electron gain enthalpy.
|
Column I (Electronic configuration) |
Column II ' (Electron gain enthalpy/kJ moL-1 |
| (i) 1s2 2s2 2p6 | A. -53 |
| (ii) ls22s22p63sl | B. -328 |
| (iii) ls22s22p5 | C. -141 |
| (iv) 1s2 2S2 2p4 | D. +48 |
Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.
Write down the outermost electronic configuration of alkali metals. How will you justify their placement in group 1 of the periodic table?