Chapter 3 - Classification of Elements and Periodicity in Properties

How does electronegativity and non – metallic character related to each
other?

Why does electronegativity value increases across a period and decreases
down period?

Why does the ionization enthalpy gradually decreases in a group?

Why are elements at the extreme left and extreme right the most reactive?

The atomic number of an element is 16. Determine its position in accordance
to its electronic configuration.

Arrange the following elements in the increasing order of metallic character :
Si, Be, Mg, Na, P.

Why do Na and K have similar properties?

What is the general outer electronic configuration of f – block elements?

Why does lithium form covalent bond unlike other alkali which forms ionic
bond?

Define a neutral oxide.

What is an amphoteric oxide?

Give the properties of the oxides in a particular period.

How does the reactivity of non–metals changes in a period and group?

How do metals react in a period?

What is the valency of noble gases?

How does valency vary in a group and period in the periodic table?

Define valency.

Na+ has higher value of ionization enthalpy than Ne, though both have same
electronic configuration.

Among the elements B, Al, C and Si
(a) Which has the highest first ionization enthalpy?
(b) Which has the largest atomic radius?

The size of an atom can be expressed by three radii. Name them. Which of
these given the highest, and the lowest value of the atomic radius of an
element?

How does atomic size change in a group?

Define ionization enthalpy and electron gain enthalpy?

Explain why cations are smaller and anions are larger in radii than their parent
atom?

The atomic radius of elements decreases along the period but Neon has highest
size among III period element? Why

Why Li and Mg show resemblance in chemical behaivour?

How does atomic size change in a group?

Predict the position of the element in the periodic table satisfying the

electronic configuration (n-1) d¹ ns² for n=4,

Give the main features of f-block elements.

Give the main features of p-block elements.

Give the main features of s-block elements.

What is the electronic configuration when elements are classified group
wise?

Define electronic configuration.

In short give the features of the seven periods.

Give the general characteristics of the long form of Modern periodic table?

Describe the main features of Mendeleev’s periodic table?

Name the two elements whose existence and properties were predicted by
Mendeleev though they did not exist then.

How did Mendeleev arrange the elements?

Define and state Mendeleev’s periodic law.

Stale the modern ‘Periodic law’?

What is the basis of triad formation of elements?

Who was the first scientist to classify elements according to their properties?

How many elements are known at present?

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

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

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.

(c) End of valence electrons is marked by a big jump in ionization enthalpy.

(d) Removal of electron from orbitals bearing lower n value is easier than from orbital having higher n value.

The size of isoelectronic species — F^-, Ne and Na⁺ is affected by

(a) Nuclear charge (Z )

(b) Valence principal quantum number (n)

(c) Electron-electron interaction in the outer orbitals

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

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)

(c) Nuclear mass

(d) Number of core electrons.

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.

(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.

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

(a) Atomic number

(b) Atomic mass

(c) Principal quantum number

(d) Azimuthal quantum number.

Predict the formula 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) Phosphorus and fluorine              (f) Element 71 and fluorine

The first (Δ_iH1) and the second (Δ_iH) ionization enthalpies (in kJ mol^-1) and the (Δ_egH) electron gain enthalpy (in kJ mol^-1) of a few elements are given below:

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.

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.

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

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.

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.

(c) Identify an element that would tend to gain two electrons.

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

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

Would you expect the first ionization enthalpies for two isotopes of the same element to be the same or different? Justify your answer.

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

(a) gains an electron

(b) loses an electron

How would you react to the statement that the electronegativity of N on Pauling scale is 3.0 in all the nitrogen compounds?

What is the basic difference between the terms electron gain enthalpy and electronegativity?

Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.

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

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

.  

The first ionization enthalpy values (in kJmol^-1) of group 13 elements are :

How would you explain this deviation from the general trend?

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

group elements tends to decrease down a group?

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?

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 ΔiH than B

(ii) O has lower ΔiH than N and F?

Energy of an electron in the ground state of the hydrogen atom is -2.18 x 10^-18 J. Calculate the ionization enthalpy of atomic hydrogen in terms of J mol^-1.

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.

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

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.

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⁺

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

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

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

Which element do you think would have been named by

(i) Lawrence Berkeley Laboratory

(ii) Seaborg's group?

Write the atomic number of the element present in the third period and seventeenth group of the periodic table.

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

On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.

What is the basic difference in approach between the Mendeleev's Periodic Law and the Modern Periodic Law?