(b) As one moves down the group, the electron gain enthalpy decreases because the atomic size grows and the new electron is further away from the nucleus.
Assertion (A): Electron gain enthalpy becomes less negative as we go down a group.
Assertion (A): Boron has a smaller first ionization enthalpy than beryllium. Reason (R): The penetration of a 2s electron to the nucleus is more than the 2p electron, hence, 2p electron is more shielded by the inner core of electrons that the 2s electrons.
(a) Assertion and reason both are correct statements but reason is not correct explanation of assertion.
(b) Assertion is correct statement but reason is wrong statement.
(c) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(d) Assertion and reason both are wrong statement.
(c) Because beryllium (1s2 2s2) has a fully filled, boron (1s2 2s2 2p1) has a lower initial ionisation enthalpy than beryllium (1s2 2s2). s-subshell. When compared to 2s-electrons, 2s-electrons are...
Assertion and Reason Type Questions
In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given.
Choose the correct option out of the choices given below each question.
Assertion (A): Generally, ionization enthalpy increases from left to right in a period.
Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.
(a) Assertion is correct statement and reason is wrong statement.
(b) Assertion and reason both are correct statements and reason is correct explanation of assertion.
(c) Assertion and reason both are wrong statements.
(d) Assertion is wrong statement and reason is correct statement.
(b) As atomic size decreases, the ionization enthalpy increases from left to right over time. The effective nuclear charge of the electrons in the subshell is about the same.
Define ionisation enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.
The energy required by an isolated, gaseous atom in its ground state to remove an electron is known as ionization enthalpy. The valence electrons are shielded by the inner electrons, which reduces...
Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.
The factors affecting electron gain enthalpy and the trend in its variation in the periodic table are: Atomic size - As the distance between the nucleus and the outermost shell rises, the tendency...
Among alkali metals which element do you expect to be least electronegative and why?
Because electronegativity decreases as we move down the group, caesium is the least electronegative alkali metal. Cesium is a group 1 element with the biggest size due to a drop in the effective...
The radius of Na+ cation is less than that of Na atom. Give reason.
The sodium atom loses one electron to form a sodium cation, and the effective nuclear charge on the ion increases on the left electrons after the cation is formed, resulting in a decrease in radius.
How does the metallic and non-metallic character vary on moving from left to right in a period?
Metallic character reduces as we move from left to right across the period, whereas non-metallic character increases as ionization enthalpy and electron gain enthalpy increase across the period
Explain the following:
(a) Electronegativity of elements increases on moving from left to right in the periodic table.
(b) Ionisation enthalpy decrease in a group from top to bottom?
(a) The size of the atoms reduces as we move from left to right in a period due to an increase in the effective nuclear charges on the outermost electron. As a result, as you move from left to right...
Explain the deviation in ionisation enthalpy of some elements from the general trend by using the given figure:
Solution: Ionization enthalpy of elements varies through period and group. As we move from left to right in a period, the ionization enthalpy increases and lowers when we move down a group....
Arrange the elements N, P, O and S in the order of-
(i) increasing first ionisation enthalpy.
(ii) increasing non-metallic character.
Give the reason for the arrangement assigned.
(i) The ascending order of the initial ionization enthalpy is S< P< O< N. The ionization enthalpy drops as we move down the group and increases as we move along the period, but in the case...
What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.
Exothermic reaction: An exothermic reaction is a reaction in which heat is released during the reaction. For instance, Cao + CO2→ CaCO3 ΔH=-178kJmol-1 Endothermic reaction: An endothermic reaction...
How would you explain the fact that first ionisation enthalpy of sodium is lower than that of magnesium but its second ionisation enthalpy is higher than that of magnesium?
When sodium loses an electron from its outermost shell, it achieves a stable state. As a result, its initial ionization enthalpy is lower than that of magnesium. However, in the case of second...
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.
ACIDIC OXIDES Acidic oxides are oxides that react with water to produce acids. SO2, B2O3 are acidic oxides and p block elements. The chemical equation for the reaction of B2O3 with water:- B2O3 +3...
The first member of each group of representative elements (i.e., s and p-block elements) shows anomalous behaviour. Illustrate with two examples.
Examples include lithium and beryllium. The initial group element is Li. It has variety of characteristics and forms, including covalent compounds and nitrides. The second group's initial element is...
Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.
The ionization enthalpy of oxygen is lower than that of nitrogen because when one electron is removed from oxygen, it easily donates it to achieve half-filled stability, whereas removing one...
Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.
Ti has an atomic number of 22 and an electronic configuration of [Ar]3d24s2. It may be found in various compounds with three different oxidation states of +2,+3, and +4 such as TiO2(+4), Ti2O3(+3),...
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
(ii) 160, 160
(iii) 72, 72
(iv) 160, 72
(i) 72, 160 Neon has van der Waal's radii and fluorine has covalent radii. The covalent radius is always less than van der Waal's radius, Fluorine has a radius of 72pm while Neon has a radius of...
Write four characteristic properties of p-block elements.
They have a wide range of oxidation states. The reducing character increases as we move down the group, while the oxidizing character increases across the period. The ionization enthalpy of these...
Among the elements B, Al, C and Si,
(i) which element has the highest first ionisation enthalpy?
(ii) which element has the most metallic character? Justify your answer in each case.
(i) The ionization enthalpy of carbon is the highest. It rises from left to right along the period and then decreases as we move down the group. (ii) The most metallic element is aluminium. The...
The statement that is not correct for periodic classification of elements is:
(i) The properties of elements are periodic function of their atomic numbers.
(ii) Non-metallic elements are less in number than metallic elements.
(iii) For transition elements, the 3d-orbitals are filled with electrons after3p-orbitals and before 4s-orbitals.
(iv) The first ionisation enthalpies of elements generally increase withincrease in atomic number as we go along a period.
Option (iii) is the answer. The Aufbau principle describes how electrons first fill low-energy orbitals (near to the nucleus) before moving on to higher-energy orbitals. They fill the orbitals...
Ionisation enthalpies of elements of the second period are given below: Ionisation enthalpy/ kcal mol–1: 520, 899, 801, 1086, 1402, 1314, 1681, 2080. Match the correct enthalpy with the elements and complete the graph given in Fig. 3.1. Also, write symbols of elements with their atomic number.
Solution: N has a higher first ionisation enthalpy than O, despite the fact that O has a higher nuclear charge. This is because the electron in N must be removed from a more stable, exactly...
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.
The modern periodic table has 118 elements divided into seven periods. As a result, the element with atomic number 119 will be in the 8th period of the first group and will have the electronic...
All transition elements are d-block elements, but all d-block elements do not transition elements. Explain.
D block elements are those that have their outermost shell filled with d electrons. Because incompletely filled d orbitals are crucial for elements like calcium and zinc, all d block elements are...
Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.
Fluorine has a lower size than chlorine, which means there is less attraction outside the shell to gain an electron. In addition, inter-electronic repulsions exist in the 2p orbitals, resulting in a...
An element belongs to the 3rd period and group-13 of the periodic table. Which of the following properties will be shown by the element?
(i) Good conductor of electricity
(ii) Liquid, metallic
(iii) Solid, metallic
(iv) Solid, non-metallic
Option (i) and (iii) are the answers. The element belonging to 3rd period and 13th group is aluminium which is a metal. Hence, it is solid, metallic and good conductor of electricity.
Ionic radii vary in
(i) inverse proportion to the effective nuclear charge.
(ii) inverse proportion to the square of effective nuclear charge.
(iii) direct proportion to the screening effect.
(iv) direct proportion to the square of screening effect.
Option (i) and (iii) are the answers. Ionic radii decreases as the effective nuclear charge increases due to inverse proportional relation. Also, ionic radii increases as the screening effect...
Which of the following have no unit?
(i) Electronegativity
(ii) Electron gain enthalpy
(iii) Ionisation enthalpy
(iv) Metallic character
Option (i) and (iv) are the answers. Electron gain enthalpy and ionization enthalpy have units of enthalpy.
In which of the following options order of arrangement does not agree with
the variation of property indicated against it?
(i) Al3+ < Mg2+ < Na+ < F– (increasing ionic size)
(ii) B < C < N < O (increasing first ionisation enthalpy)
(iii) I < Br < Cl < F (increasing electron gain enthalpy)
(iv) Li < Na < K < Rb (increasing metallic radius)
Option (ii) and (iiii) are the answers. For increasing first ionization enthalpy, the order should be: B < C < O < N For increasing electron gain enthalpy, the order should be: I < Br...
Which of the following sets contain only isoelectronic ions?
\[\left( \mathbf{i} \right)\text{ }\mathbf{Z}{{\mathbf{n}}^{\mathbf{2}+}},\text{ }\mathbf{C}{{\mathbf{a}}^{\mathbf{2}+}},\text{ }\mathbf{G}{{\mathbf{a}}^{\mathbf{3}+}},\text{ }\mathbf{A}{{\mathbf{l}}^{\mathbf{3}+}}\]
\[\left( \mathbf{ii} \right)\text{ }{{\mathbf{K}}^{+}},\text{ }\mathbf{C}{{\mathbf{a}}^{\mathbf{2}+}},\text{ }\mathbf{S}{{\mathbf{c}}^{\mathbf{3}+}},\text{ }\mathbf{C}{{\mathbf{l}}^{}}\]
\[\left( \mathbf{iii} \right)\text{ }{{\mathbf{P}}^{\mathbf{3}-}},\text{ }{{\mathbf{S}}^{\mathbf{2}-}},\text{ }\mathbf{C}{{\mathbf{l}}^{}},\text{ }{{\mathbf{K}}^{+}}\]
\[\left( \mathbf{iv} \right)\text{ }\mathbf{Ti}{{~}^{\mathbf{4}+}},\text{ }\mathbf{Ar},\text{ }\mathbf{C}{{\mathbf{r}}^{\mathbf{3}+}},\text{ }{{\mathbf{V}}^{\mathbf{5}+}}\]
Option (ii) and (iii) are the answers. (i) Zn2+ (30 – 2 = 28), Ca2+ (20 – 2 = 18), Ga3+ (31-3= 28), Al3+ (13 – 3 = 10) are not isoelectronic. (ii) K+ (19 – 1 = 18), Ca2+ (20 – 2 = 18), Sc3+ (21 – 3...
Which of the following statements are correct?
(i) Helium has the highest first ionisation enthalpy in the periodic table.
(ii) Chlorine has less negative electron gain enthalpy than fluorine.
(iii) Mercury and bromine are liquids at room temperature.
(iv) In any period, the atomic radius of alkali metal is the highest.
Option (i), (iii) and (iv) are the answers. Because of its larger size and lower electronic repulsion, chlorine has a higher negative electron gain enthalpy than fluorine.
Which of the following elements will gain one electron more readily in comparison to other elements of their group?
(i) S (g)
(ii) Na (g)
(iii) O (g)
(iv) Cl (g)
Option (i) and (iv) are the answers. Chlorine has the strongest tendency to gain an electron, as well as a high electron gain enthalpy (-ve). Group 16 includes O and S, however S has a higher...
Which of the following sequences contain atomic numbers of only representative elements?
(i) 3, 33, 53, 87
(ii) 2, 10, 22, 36
(iii) 7, 17, 25, 37, 48
(iv) 9, 35, 51, 88
Option (i) and (iv) are the answers. Representative elements are elements from the 5 and p-blocks. Transition elements belong to the f-block (Z=21–30; 39–48; 57 and 72–80; 89 and 104–112), while...
Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of the spectrum). The elements of which of the following groups will impart colour to the flame?
(i) 2
(ii) 13
(iii) 1
(iv) 17
Option (i) and (iii) are the answers. Ionization enthalpies are low in group 1 (alkali metals) and group 2 (alkaline earth metals). As a result, they give flame colour.
Which of the following elements can show covalency greater than 4?
(i) Be
(ii) P
(iii) S
(iv) B
Option (ii) and (iii) are the answers. Because P and S have d-orbitals in their valence shells, they can hold more than eight electrons in their valence shells. As a result, they have a covalency of...
Electronic configurations of four elements A, B, C and D are given below :
\[\left( \mathbf{A} \right)\text{ }\mathbf{1}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{p}}^{\mathbf{6}}}~\]
\[\left( \mathbf{B} \right)\text{ }\mathbf{1}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{p}}^{\mathbf{4}}}\]
\[\left( \mathbf{C} \right)\text{ }\mathbf{1}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{p}}^{\mathbf{6}}}~\mathbf{3}{{\mathbf{s}}^{\mathbf{1}}}~\]
\[\left( \mathbf{D} \right)\text{ }\mathbf{1}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{s}}^{\mathbf{2}}}~\mathbf{2}{{\mathbf{p}}^{\mathbf{5}}}\]
Which of the following is the correct order of increasing tendency to gain electron :
(i) A < C < B < D
(ii) A < B < C < D
(iii) D < B < C < A
(iv) D < A < B < C
Option (i) is the answer. (a) A – Is2 2s2 2p6 – Noble gas configuration B -1s2 2s2 2p4 – 2 electrons short of stable configuration C – 1s2 2s2 2p6 3.?1 – Requires one electron to complete 5-orbital...
Comprehension given below is followed by some multiple-choice questions.
Each question has one correct option. Choose the correct option.
In the modern periodic table, elements are arranged in order of increasingatomic numbers which are related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic the table has been divided into four blocks, viz, s, p, d and f. The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Aufbau principle, the seven periods (1 to 7) have 2, 8, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.
(i) The element with atomic number 57 belongs to
(a) s-block
(b) p-block
(c) d-block
(d) f-block
(ii) The last element of the p-block in 6th period is represented by the outermost electronic configuration.
(a) 7s2 7p6
(b) 5f 14 6d10 7s 2 7p 0
(c) 4f 14 5d10 6s2 6p6
(d) 4f 14 5d10 6s 2 6p 4
(iii) Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set up of the long form of the periodic table?
(a) 107
(b) 118
(c) 126
(d) 102
(e) The electronic configuration of the element which is just above the element with atomic number 43 in the same group is ________.
(a) 1s2 2s2 2p6 3s2 3p6 3d5 4s2
(b) 1s2 2s2 2p6 3s2 3p6 3d5 4s3 4p6
(c) 1s2 2s2 2p6 3s2 3p6 3d6 4s2
(d) 1s2 2s2 2p6 3s2 3p6 3d7 4s2
(v) The elements with atomic numbers 35, 53 and 85 are all ________.
(a) noble gases
(b) halogens
(c) heavy metals
(d) light metals
The formation of the oxide ion, O2- (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below:
\[\mathbf{O}\text{ }\left( \mathbf{g} \right)\text{ }+\text{ }\mathbf{e}\text{ }\to \text{ }{{\mathbf{O}}^{-}}\left( \mathbf{g} \right)\text{ };\text{ };\text{ }\text{ }\mathbf{HV}\text{ }=\text{ }\text{ }\mathbf{141}\text{ }\mathbf{kJ}\text{ }\mathbf{mol}\mathbf{1}\]
\[{{\mathbf{O}}^{-}}\left( \mathbf{g} \right)\text{ }+\text{ }\mathbf{e}\text{ }\to \text{ }{{\mathbf{O}}^{\mathbf{2}-}}\left( \mathbf{g} \right)\text{ };\text{ }\text{ }\mathbf{HV}\text{ }=\text{ }+\text{ }\mathbf{780}\text{ }\mathbf{kJ}\text{ }\mathbf{mol}\mathbf{1}\]
Thus the process of formation of O2– in the gas phase is unfavourable even though O2- is isoelectronic with neon. It is due to the fact that
(i) oxygen is more electronegative.
(ii) addition of electron in oxygen results in larger size of the ion.
(iii) electron repulsion outweighs the stability gained by achieving a noble gas configuration.
(iv) O- ion has a comparatively smaller size than an oxygen atom.
Option (iii) is the answer. This is due to the fact that when an electron is introduced to a negatively charged ion, it is repelled rather than attracted. As a result, the addition of the second...
Which of the following is the correct order of the size of the given species:
\[~\left( \mathbf{i} \right)\text{ }\mathbf{I}\text{ }>\text{ }{{\mathbf{I}}^{-}}>\text{ }{{\mathbf{I}}^{+}}^{{}}\]
\[\left( \mathbf{ii} \right)\text{ }\mathbf{I}+>\text{ }{{\mathbf{I}}^{-}}>\text{ }\mathbf{I}\]
\[\left( \mathbf{iii} \right)\text{ }\mathbf{I}\text{ }>\text{ }{{\mathbf{I}}^{+}}>\text{ }{{\mathbf{I}}^{-}}\]
\[\left( \mathbf{iv} \right)\text{ }{{\mathbf{I}}^{-}}>\text{ }\mathbf{I}\text{ }>\text{ }{{\mathbf{I}}^{+}}^{{}}\]
Option (iv) is the answer. The size of an anion, cation, and neutral species for a given element is in this order: anion>element>cation. Because of its higher z-effective, cation has the...
The elements in which electrons are progressively filled in 4f-orbital are called
(i) actinoids
(ii) transition elements
(iii) lanthanoids
(iv) halogens
Option (iii) is the answer. In lanthanoids, the 4f orbital is gradually filled with electrons. Lanthanoids have a broad electrical configuration. [Xe]4f 1-145d0-16s2.
The period number in the long form of the periodic table is equal to
(i) magnetic quantum number of any element of the period.
(ii) an atomic number of any element of the period.
(iii) maximum Principal quantum number of any element of the period.
(iv) maximum Azimuthal quantum number of any element of the period.
Option (iii) is the answer. Period number = maximum n of any element where 'n' stands for the principle quantum number. It determines the element's period number. Mg, for example, has a maximum main...
The first ionisation enthalpies of Na, Mg, Al and Si are in the order:
(i) Na < Mg > Al < Si
(ii) Na > Mg > Al > Si
(iii) Na < Mg < Al < Si
(iv) Na > Mg > Al < Si
Option (i) is the answer. Ionization enthalpy is the enthalpy change associated with the loss of the first electron from an isolated gaseous atom in its ground state. As we move across the period,...
The order of screening effect of electrons of s, p, d and f orbitals of a given shell of an atom on its outer shell electrons is:
(i) s > p > d > f
(ii) f > d > p > s
(iii) p < d < s > f
(iv) f > p > s > d
Option (i) is the answer. In every atom with more than one electron shell, this effect, known as the screening effect, describes the decrease in attraction between an electron and the nucleus. The...
Which of the following is not an actinoid?
(i) Curium (Z = 96)
(ii) Californium (Z = 98)
(iii) Uranium (Z = 92)
(iv) Terbium (Z = 65)
Option (iv) is the answer. Any group of 15 elements in the periodic table, ranging from actinium to lawrencium (atomic numbers 89–103), is known as an actinoid element. As evident from the...
Consider the isoelectronic species, Na+, Mg2+, F–and O2–. The correct order of increasing length of their radii is _________.
\[\left( \mathbf{i} \right)\text{ }{{\mathbf{F}}^{}}~<\text{ }{{\mathbf{O}}^{\mathbf{2}-}}~<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}\]
\[\left( \mathbf{ii} \right)\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}<\text{ }{{\mathbf{F}}^{}}<\text{ }{{\mathbf{O}}^{\mathbf{2}-}}\]
\[\left( \mathbf{iii} \right)\text{ }{{\mathbf{O}}^{\mathbf{2}-}}<\text{ }{{\mathbf{F}}^{}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}\]
\[\left( \mathbf{iv} \right)\text{ }{{\mathbf{O}}^{\mathbf{2}-}}~<\text{ }{{\mathbf{F}}^{}}~<\text{ }\mathbf{M}{{\mathbf{g}}^{\mathbf{2}+}}~<\text{ }\mathbf{N}{{\mathbf{a}}^{+}}\]
Option (ii) is the answer. Radius of elements increase as we move from left to right in a period. These are isoelectronic species having same number of electrons. As we move from left to right, from...