Which of the following pairs of elements would have a move negative electron gain enthalpy? (i) O or F (ii) F or Cl.
(i) O or F. Both O and F lie in 2nd period. As we move from O to F the atomic size decreases.
Due to smaller size of F nuclear charge increases.
Further, gain of one electron by
F —> F–
F~ ion has inert gas configuration, While the gain of one electron by
0->O–
gives CT ion which does not have stable inert gas configuration, consequently, the energy released is much higher in going from
F ->F–
than going from O >O–
In other words electron gain enthalpy of F is much more negative than that of oxygen.
(ii) The negative electron gain enthalpy of Cl (∆ eg H = – 349 kj mol-1) is more than that of F (∆ eg H = – 328 kJ mol -1).
The reason for the deviation is due to the smaller size of F. Due to its small size, the electron repulsions in the relatively compact 2p-subshell are comparatively large and hence the attraction for incoming electron is less as in the case of Cl.
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.
What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down the group?
What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.
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?
What do you understand by ‘Representative elements’? Name the groups whose elements are called representative elements.
Which of the following elements can show covalency greater than 4?
(a) Be (b) P (c) S (d) B
Explain the deviation in ionization enthalpy of some elements from the general trend by using the given figure.
An element belongs to 3rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(a) Good conductor of electricity
(b) Liquid, metallic
(c) Solid, metallic
(d) Solid, non metallic
Which of the following sequences contain atomic numbers of only representative elements?
(a) 3, 33, 53, 87
(b) 2, 10, 22, 36
(c) 7, 17,25,37,48
(d) 9,35,51,88
Explain the following:
(a) Electronegativity of elements increases on moving from left to right in the periodic table.
(b) Ionisation enthalpy decreases in a group from top to bottom.
Discuss the main features of long form of the periodic table. What are the advantages of long . form of periodic table?
The first ionisation enthalpy of magnesium is higher than that of sodium. On the other hand, the second ionisation enthalpy of sodium is very much higher than that of magnesium. Explain.
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.
Considering the elements F, Cl, O and N, the correct order of their chemical reactivity in terms of oxidising property is:
(a) F > Cl> O > N (b) F > O > Cl> N (c) Cl> F > O > N (d) O > F > N > Cl
Explain why chlorine can be converted into chloride ion more easily as compared to fluoride ion from fluorine ?
Which of the following sets contain only isoelectronic ions?
(a) Zn2+, Ca2+, Ga3+, Al3+
(b) K+, Ca2+, Sc3+, Cl–
(c) P3-, S2- Cl–,K+
(d) Ti4+, Ar, Cl3+, V5+
First member of each group of representative elements (i.e., s and p-block elements) shows anomalous behaviour. Illustrate with two examples.
Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.
On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
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?
How would you react to the statement that the electronegativity ofN on Pauling scale is 3.0 in all the nitrogen compounds?
Use periodic table to answer the following questions:
(a) Identify the element with five electrons in the outer subshell.
(b) Identify the element that would tend to lose two electrons.
(c) Identify the element that would tend to gain two electrons.
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?
Which of the following statements related to the modem periodic table is incorrect?
(a) The p-block has six columns, because a maximum of 6 electrons can occupy all the orbitals in a p-subshell.
(b) The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell.
(c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell.
(d) The block indicates value of azimuthal quantum number (l)for the last subshell that received electrons in building up the electronic configuration.
Define electron gain enthalpy. What are its units? Discuss the factors which influence the electron gain enthalpy.
Consider the isoelectronic species, Na+, Mg2+, F and O2-. The correct order of increasing length of their radii is
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
How does the metallic and non metallic character vary on moving from left to right in a period?
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?
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 is basic difference between the terms electron gain enthalpy and electro negativity?
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
Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.
Would you expect the first ionization enthalpies of two isotopes of the same element to be the same or different? Justify your answer.