(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.
(a) Variation of atomic radius in a group:
On moving down the group there is an increase in the principal quantum number and therefore no. of electron shells increases and thus the atomic size increases. Thus the atomic radii of the element increases.
(b) (i) Radius of cation is less than that of the atom:
Since the cation is formed by losing of one or more electrons.
For example,
Na —> Na++ e–
Thus the radius of Na+will be less than the Na.
(ii) Radius of anion is more than that of the atom.
Since the anion is formed by gaining one or more electron. Therefore, the atomic radius is larger than the corresponding atom.
(iii) In iso-electronic ions, atoms have same number of electrons but different magnitude of nuclear charges. As the nuclear charge increases ionic radius decreases.
For example. N3-, O2-, F– have same No. of electrons = 10 but different ionic radii = 171, 140, 136 respectively.
Discuss the main characteristics of four blocks of elements in the periodic table? Give their general electronic configuration.
Ionisation enthalpies of elements of second period are given below:
Ionisation enthalpy/kJ mol-1: 520, 899, 801, 1086, 1402, 1314, 1681, 2080. Match the correct enthalpy with the elements and complete the graph given in figure. Also write symbols of elements with their atomic number.
Considering the elements B, Al, Mg and K, the correct order of their metallic character is:(a) B> Al> Mg > K(b) Al> Mg > B> K (c) Mg > Al> K> B (d) K> Mg > Al> B
Write down the outermost electronic configuration of alkali metals. How will you justify their placement in group 1 of the periodic table?
What is the basic difference in approach between Mendeleev’s Periodic Law and the Modem Periodic Law?
How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?
Discuss the main features of long form of the periodic table. What are the advantages of long . form of periodic table?
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?
Define electron gain enthalpy. What are its units? Discuss the factors which influence the electron gain enthalpy.
Assign the position of the element having outer electronic configuration,
(i) ns2 np4 for n = 3 (ii) (n – 1) d2 ns2 for n = 4 and (iii) (n – 2) f7 (n – 1) d1 ns2 for n = 6 in the periodic table?
Consider the isoelectronic species, Na+, Mg2+, F and O2-. The correct order of increasing length of their radii is
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
On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
Show by a chemical reaction with water that Na20 is a basic oxide and Cl207 is an acidic oxide.
Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.
Write the atomic number of the element present in the third period and seventeenth group of the periodic table.
Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.
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.
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
First member of each group of representative elements (i.e., s and p-block elements) shows anomalous behaviour. Illustrate with two examples.
What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.
Which of the following pairs of elements would have a move negative electron gain enthalpy? (i) O or F (ii) F or Cl.
In the modem periodic table, the period indicates the value of
(a)atomic number (b) mass number (c) principal quantum number (d) azimuthal quantum number?
The first ionization enthalpies of Na, Mg, A1 and Si are in the order
(a) Na < Mg > A1 < Si
(b) Na>Mg>Al>Si
(c) Na < Mg < A1 < Si
(d) Na > Mg > A1 < Si
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.
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.
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 |
How do atomic radius vary in a period and in a group? How do you explain the variation?
What is the significance of the terms – isolated gaseous atom and ground state while defining the ionization enthalpy and electron gain enthalpy?[Hint: Requirements for comparison purposes]
Considering the elements B, C, N, F and Si, the correct order of their non-metallic character is: (a) B>C>Si>N>F (b) Si>C>B>N>F (c) F>N>C>B>Si (d) F>N>C>Si>B
Explain why chlorine can be converted into chloride ion more easily as compared to fluoride ion from fluorine ?
The electronic configuration of an element is Is 2s 2p 3s 3p 4s . Locate the element in the periodic table.
What is the cause of periodicity in properties of the elements? Explain with two examples.
(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.
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
