H1: CLASSIFICATION OF ELEMENTSAND PERIODICITY IN PROPERTIES

EXERCISES

3.1 What is the basic theme of organisation in the periodic table?

3.2 Which important property did Mendeleev use to classify the elements in his periodic

table and did he stick to that?

3.3 What is the basic difference in approach between the Mendeleev’s Periodic Law

and the Modern Periodic Law?

3.4 On the basis of quantum numbers, justify that the sixth period of the periodic

table should have 32 elements.

3.5 In terms of period and group where would you locate the element with Z =114?

3.6 Write the atomic number of the element present in the third period and seventeenth

group of the periodic table.

3.7 Which element do you think would have been named by

(i) Lawrence Berkeley Laboratory

(ii) Seaborg’s group?

3.8 Why do elements in the same group have similar physical and chemical properties?

3.9 What does atomic radius and ionic radius really mean to you?

3.10 How do atomic radius vary in a period and in a group? How do you explain the

variation?

3.11 What do you understand by isoelectronic species? Name a species that will be

isoelectronic with each of the following atoms or ions.

(i) F– (ii) Ar (iii) Mg2+ (iv) Rb+

3.12 Consider the following species :

N3–, O2–, F–, Na+, Mg2+ and Al3+

(a) What is common in them?

(b) Arrange them in the order of increasing ionic radii.

3.13 Explain why cation are smaller and anions larger in radii than their parent atoms?

3.14 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.

3.15 Energy of an electron in the ground state of the hydrogen atom is

–2.18×10–18J. Calculate the ionization enthalpy of atomic hydrogen in terms of

J mol–1.

Hint: Apply the idea of mole concept to derive the answer.

3.16 Among the second period elements the actual ionization enthalpies are in the

order Li < B < Be < C < O < N < F < Ne.

Explain why

(i) Be has higher Äi H than B

(ii) O has lower Äi H than N and F?

3.17 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?

3.18 What are the various factors due to which the ionization enthalpy of the main

group elements tends to decrease down a group?

3.19 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 ?

3.20 Which of the following pairs of elements would have a more negative electron gain

enthalpy?

(i) O or F (ii) F or Cl

3.21 Would you expect the second electron gain enthalpy of O as positive, more negative

or less negative than the first? Justify your answer.

3.22 What is the basic difference between the terms electron gain enthalpy and

electronegativity?

3.23 How would you react to the statement that the electronegativity of N on Pauling

scale is 3.0 in all the nitrogen compounds?

3.24 Describe the theory associated with the radius of an atom as it

(a) gains an electron

(b) loses an electron

3.25 Would you expect the first ionization enthalpies for two isotopes of the same element

to be the same or different? Justify your answer.

3.26 What are the major differences between metals and non-metals?

3.27 Use the periodic table to answer the following questions.

(a) Identify an element with five electrons in the outer subshell.

(b) Identify an element that would tend to lose two electrons.

(d) Identify the group having metal, non-metal, liquid as well as gas at the room

temperature.

3.28 The increasing order of reactivity among group 1 elements is Li < Na < K < Rb <Cs

whereas that among group 17 elements is F > CI > Br > I. Explain.

3.29 Write the general outer electronic configuration of s-, p-, d- and f- block elements.

3.30 Assign the position of the element having outer electronic configuration

(i) ns2np4 for n=3 (ii) (n-1)d2ns2 for n=4, and (iii) (n-2) f 7 (n-1)d1ns2 for n=6, in the

periodic table.

3.31 The first (ÄiH1) and the second (ÄiH2) ionization enthalpies (in kJ mol–1) and the

(ÄegH) electron gain enthalpy (in kJ mol–1) of a few elements are given below:

Elements ÄH1 ÄH2 ÄegH

I 520 7300 –60

II 419 3051 –48

III 1681 3374 –328

IV 1008 1846 –295

V 2372 5251 +48

VI 738 1451 –40

Which of the above elements is likely to be :

(a) the least reactive element.

(b) the most reactive 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)?

3.32 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

(e) Phosphorus and fluorine (f) Element 71 and fluorine

3.33 In the modern periodic table, the period indicates the value of :

(a) atomic number

(b) atomic mass

(d) azimuthal quantum number.

3.34 Which of the following statements related to the modern periodic table is incorrect?

(a) The p-block has 6 columns, because a maximum of 6 electrons can occupy all

the orbitals in a p-shell.

(b) The d-block has 8 columns, because a maximum of 8 electrons

can occupy all the orbitals in a d-subshell.

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.

3.35 Anything that influences the valence electrons will affect the chemistry

of the element. Which one of the following factors does not affect the

valence shell?

(a) Valence principal quantum number (n)

(b) Nuclear charge (Z )

(d) Number of core electrons.

3.36 The size of isoelectronic species — F–, Ne and Na+ is affected by

(a) nuclear charge (Z )

(b) valence principal quantum number (n)

(d) none of the factors because their size is the same.

3.37 Which one of the following statements is incorrect in relation to

ionization enthalpy?

(a) Ionization enthalpy increases for each successive electron.

(b) The greatest increase in ionization enthalpy is experienced on

removal of electron from core noble gas configuration.

enthalpy.

(d) Removal of electron from orbitals bearing lower n value is easier

than from orbital having higher n value.

3.38 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

3.39 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

3.40 Considering the elements F, Cl, O and N, the correct order of their

chemical reactivity in terms of oxidizing property is :

(a) F > Cl > O > N (b) F > O > Cl > N

HOME

CLASSIFICATION OF ELEMENTSAND PERIODICITY IN PROPERTIES