Question:

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

Answer:

Step 1: Determine the group and period of the element.

Group: Group 14 (IVA) Period: Period 7

Step 2: Locate the element on the Periodic Table.

Element with Z = 114 can be located in Group 14 (IVA) and Period 7 of the Periodic Table.

Question:

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⁺

Answer:

Isoelectronic species are species with the same number of electrons.

i) F⁻ and Cl⁻ ii) Ar and Ne iii) Mg²⁺ and Ca²⁺ iv) Rb⁺ and K⁺

Question:

Consider the following species : N^3- , O^2- ,F⁻, Na⁺ , Mg²⁺ and Al³⁺ (a) What is common in them? (b) Arrange them in the order of increasing ionic radii.

Answer:

(a) What is common in them? Answer: All of the species listed are ions.

(b) Arrange them in the order of increasing ionic radii. Answer: F⁻ < N³⁻ < O²⁻ < Na⁺ < Mg²⁺ < Al³⁺

Question:

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.

Answer:

1. Convert the given energy into molar energy by using the Avogadro’s number.

Energy of an electron in the ground state of the hydrogen atom (n=1) = -2.18 x 10⁻¹⁸ J

Molar energy of an electron in the ground state of the hydrogen atom = -2.18 x 10⁻¹⁸ J x 6.022 x 10²³ mol⁻¹ = -13.2 x 10⁻⁵ J mol⁻¹

2. Calculate the ionization enthalpy of atomic hydrogen.

Ionization enthalpy of atomic hydrogen = 13.2 x 10⁻⁵ J mol⁻¹ - (-13.2 x 10⁻⁵ J mol⁻¹) = 26.4 x 10⁻⁵ J mol⁻¹

Question:

Which of the following pair of elements would have a more negative electron gain enthalpy? (i) O or F (ii) F or Cl

Answer:

(i) F would have a more negative electron gain enthalpy than O.

(ii) Cl would have a more negative electron gain enthalpy than F.

Question:

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

Answer:

Answer: The second electron gain enthalpy of oxygen would be more negative than the first. This is because the second electron would be entering a higher energy level, so it would require more energy to be removed from the system for the electron to be added.

Question:

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

Answer:

Answer: The first ionization enthalpies for two isotopes of the same element are expected to be different. This is because isotopes of the same element have different atomic masses, and thus, different amounts of energy are required to remove the outermost electron from the atom. Therefore, the first ionization enthalpies for two isotopes of the same element will be different.

Question:

Write any three differences between metals and non-metals with respect to their physical properties.

Answer:

1. Metals are generally hard, whereas non-metals are usually soft.
2. Metals are good conductors of heat and electricity, whereas non-metals are poor conductors.
3. Metals are usually malleable and ductile, whereas non-metals are usually brittle and cannot be stretched or molded.

Question:

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) f⁷(n-1)d¹ ns² for n=6 in the periodic table.

Answer:

(i) For n=3, the element having outer electronic configuration ns2np4 is Lithium (Li). It is located in the first group (Group 1) and second period of the periodic table.

(ii) For n=4, the element having outer electronic configuration (n-1)d²ns² is Scandium (Sc). It is located in the third group (Group 3) and third period of the periodic table.

(iii) For n=6, the element having outer electronic configuration (n-2)f⁷(n-1)d¹ns² is Zirconium (Zr). It is located in the fourth group (Group 4) and fourth period of the periodic table.

Question:

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

1. atomic number
2. atomic mass
3. principal quantum number
4. azimuthal quantum number

Answer:

Answer: 1. atomic number

Question:

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

Answer:

Answer: A : B>C>Si>N>F

Question:

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 (c) Cl > F > O > N (d) O > F > N > Cl

Answer:

Answer: (c) Cl > F > O > N

Question:

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

Answer:

1. Quantum numbers are used to describe the energy levels of electrons in an atom.

2. The number of elements in a period of the periodic table is determined by the maximum number of electrons that can occupy each energy level.

3. In the sixth period, the maximum number of electrons that can occupy the highest energy level is 32.

4. Therefore, the sixth period of the periodic table should have 32 elements.

Question:

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

Answer:

1. Atomic radius is the distance from the center of an atom to its outermost shell of electrons.

2. Ionic radius is the distance from the center of an ion to its outermost shell of electrons.

3. To me, atomic and ionic radius are important concepts that help to explain the behavior of atoms and ions in a chemical reaction. They help to explain why certain elements form certain compounds, why some elements are more reactive than others, and how the size of an atom or ion affects its reactivity. Knowing these concepts is essential for understanding how chemistry works.

Question:

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

Answer:

Step 1: Cations are positively charged ions, which are formed when an atom loses one or more electrons.

Step 2: Anions are negatively charged ions, which are formed when an atom gains one or more electrons.

Step 3: When an atom loses electrons, its nucleus becomes more positively charged and attracts the remaining electrons more strongly. This causes the electrons to be pulled closer to the nucleus, making the cation smaller than the parent atom.

Step 4: When an atom gains electrons, its nucleus becomes more negatively charged and repels the extra electrons. This causes the electrons to be pushed further away from the nucleus, making the anion larger than the parent atom.

Question:

The increasing order of reactivity among group 1 element is Li<Na<Rb<Cs, whereas that among group 17 element is F>CI>Br>I. Explain?

Answer:

Answer: Group 1 elements are known as the alkali metals and are located in the first column of the periodic table. They are highly reactive and tend to lose their single valence electron when reacting with other elements. The increasing order of reactivity among group 1 elements is due to the fact that Li has the smallest atomic radius and the least amount of shielding from its inner electrons, making it the most reactive. Na, Rb, and Cs have larger atomic radii and more shielding from their inner electrons, making them less reactive than Li.

Group 17 elements are known as the halogens and are located in the seventh column of the periodic table. They are highly reactive and tend to gain an electron when reacting with other elements. The increasing order of reactivity among group 17 elements is due to the fact that F has the smallest atomic radius and the least amount of shielding from its inner electrons, making it the most reactive. Cl, Br, and I have larger atomic radii and more shielding from their inner electrons, making them less reactive than F.

Question:

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

Answer:

1. s-block elements: The general outer electronic configuration of s-block elements is ns^1-2.

2. p-block elements: The general outer electronic configuration of p-block elements is np^1-6.

3. d-block elements: The general outer electronic configuration of d-block elements is (n-1)d^1-10.

4. f-block elements: The general outer electronic configuration of f-block elements is (n-2)f^1-14.

Question:

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
C : Nuclear mass D : Number of core electrons

Answer:

Answer: C : Nuclear mass

Question:

Which important property did Mendeleev use to classify the elements in his Periodic Table, and did he stick to that?

Answer:

1. Mendeleev used the property of atomic mass to classify the elements in his Periodic Table.

2. Yes, he stuck to that property for the majority of elements in his Periodic Table. However, he did make some exceptions for certain elements, such as placing them in a different group based on their chemical properties.

Question:

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

Answer:

Answer: Atomic number of the element present in the third period and seventeenth group of the periodic table is 33. This element is Arsenic (As).

Question:

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

Answer:

1. Elements in the same group on the periodic table are all in the same column and have the same number of valence electrons.

2. Since all elements in the same group have the same number of valence electrons, they have the same number of electrons in their outermost energy level.

3. Since all elements in the same group have the same number of electrons in their outermost energy level, they have similar electron configurations.

4. Since all elements in the same group have similar electron configurations, they have similar reactivity, which leads to similar chemical properties.

5. Since all elements in the same group have similar electron configurations, they also have similar atomic radii, which leads to similar physical properties.

6. Therefore, elements in the same group have similar physical and chemical properties.

Question:

What is the significance of the terms ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy?

Answer:

1. Isolated gaseous atom: An isolated gaseous atom is an atom that is not bonded to any other atom or molecule and is in its natural state. This is the state of an atom before it is ionized.

2. Ground state: The ground state of an atom is its lowest energy level. This is the state of an atom before it is excited or ionized.

3. Ionization enthalpy: Ionization enthalpy is the energy required to remove an electron from an isolated gaseous atom to form a positive ion.

4. Electron gain enthalpy: Electron gain enthalpy is the energy required to add an electron to an isolated gaseous atom to form a negative ion.

In conclusion, the terms ‘isolated gaseous atom’ and ‘ground state’ are important when defining ionization enthalpy and electron gain enthalpy as they are the states of the atom before it is ionized or excited.

Question:

Among the second period elements the actual ionization enthalpies are in the order Li<B<Be<C<O<N<F<Ne.

Answer:

1. Li < B
2. B < Be
3. Be < C
4. C < O
5. O < N
6. N < F
7. F < Ne

Question:

With the help of information given above, explain the followng: (i) Be has higher Δi H than B. (ii) O has lower Δi H than N and F.

Answer:

(i) Be has higher Δi H than B because the enthalpy of formation of Be is -14.78 kJ/mol, which is more negative than the enthalpy of formation of B which is -7.28 kJ/mol. This means that Be releases more energy when it is formed than B, and therefore has a higher enthalpy of formation.

(ii) O has lower Δi H than N and F because the enthalpy of formation of O is -249.21 kJ/mol, which is more positive than the enthalpy of formation of N and F which are -45.96 kJ/mol and -272.81 kJ/mol, respectively. This means that O requires more energy to be formed than N and F, and therefore has a lower enthalpy of formation.

Question:

Describe the theory associated with the radius of an atom as it : (a) gains an electron (b) loses an electron

Answer:

a) When an atom gains an electron, it increases the number of electrons in the atom’s outermost shell. This increases the radius of the atom, as the additional electron will repel the other electrons, pushing them further out from the nucleus.

b) When an atom loses an electron, it decreases the number of electrons in the atom’s outermost shell. This decreases the radius of the atom, as the missing electron will no longer repel the other electrons, allowing them to move closer to the nucleus.

Question:

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

Answer:

1. The basic theme of organization in the periodic table is the arrangement of elements according to their atomic number, electron configuration, and recurring chemical properties.

2. Elements are arranged in order of increasing atomic number, from left to right and top to bottom.

3. The elements are divided into blocks based on their electron configuration.

4. The elements within each block are organized by recurring chemical properties, such as their reactivity, melting point, and boiling point.

Question:

What is the basic difference between the Mendeleev’s Periodic Law and the Modern Periodic Law?

Answer:

1. The basic difference between Mendeleev’s Periodic Law and the Modern Periodic Law is that Mendeleev’s Periodic Law was based on the arrangement of elements in order of their atomic weights, while the Modern Periodic Law is based on the arrangement of elements in order of their atomic numbers.

2. Mendeleev’s Periodic Law was developed in 1869, while the Modern Periodic Law was developed in 1913.

3. Mendeleev’s Periodic Law was based on the observation of properties of elements, while the Modern Periodic Law is based on the arrangement of electrons in shells around the nucleus of an atom.

Question:

Which element do you think would have been named by (i) Lawrence Berkeley Laboratory and (ii) Seaborg’s group?

Answer:

(i) Lawrence Berkeley Laboratory would have named element 117, Tennessine.

(ii) Seaborg’s group would have named element 118, Oganesson.

Question:

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

Answer:

Answer:

1. Electron gain enthalpy is the energy released when an atom gains an electron, while electronegativity is a measure of an atom’s ability to attract electrons.
2. Electron gain enthalpy is a measure of the energy released when an atom gains an electron, while electronegativity is a measure of an atom’s relative ability to attract electrons.

Question:

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 (I) for the last subshell that received electrons in building up the electronic configuration

Answer:

Answer: (d) The block indicates value of azimuthal quantum number (I) for the last subshell that received electrons in building up the electronic configuration

Question:

The size of isoelectronic species; F−,Ne,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

Answer:

Answer: D : none of the factors because their size is the same

Question:

Considering the elements B,Al,Mg,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

Answer:

Answer: C : Mg>Al>K>B

Question:

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

Answer:

Step 1: An atomic radius is the distance from the nucleus of an atom to its outermost shell of electrons.

Step 2: In a period, the atomic radius decreases as you move from left to right across the period. This is because as you move across the period, the number of protons and electrons in the atom increases, but the nucleus remains the same size. This causes the electrons to be held more tightly to the nucleus, resulting in a decrease in atomic radius.

Step 3: In a group, the atomic radius increases as you move down the group. This is because as you move down the group, the number of protons and electrons in the atom increases, but the nucleus remains the same size. This causes the electrons to be held less tightly to the nucleus, resulting in an increase in atomic radius.

Question:

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?

Answer:

1. The first ionization enthalpy is the energy required to remove one mole of electrons from one mole of gaseous atoms.

2. The second ionization enthalpy is the energy required to remove a second mole of electrons from one mole of gaseous ions.

3. Sodium has a larger atomic radius than magnesium, meaning that the outermost electron in sodium is farther away from the nucleus than the outermost electron in magnesium.

4. This means that the first electron in sodium is less strongly attracted to the nucleus than the first electron in magnesium, resulting in a lower first ionization enthalpy for sodium.

5. However, once the first electron is removed from sodium, the remaining electrons become more strongly attracted to the nucleus, resulting in a higher second ionization enthalpy for sodium than for magnesium.

Question:

What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?

Answer:

Answer:

1. Increase in atomic size: As we move down a group, the atomic size of elements increases due to the addition of extra shells of electrons. This increases the distance between the nucleus and the outermost shell of electrons, thus weakening the attraction between them and thus decreasing the ionization enthalpy.

2. Shielding effect of inner shells: As we move down a group, the number of inner shells of electrons also increases. This leads to a shielding effect, i.e. the outermost electrons are shielded from the attraction of the nucleus by the inner shells of electrons. Thus, the ionization enthalpy decreases.

3. Increase in number of electrons: As we move down a group, the number of electrons in the outermost shell also increases. This increases the repulsion between the electrons and thus decreases the ionization enthalpy.

Question:

The first ionization enthalpy values ( in kJ mol−1 ) of group 13 element are : B 801, Al 577, Ga 579, In 558, Tl 589 How would you explain this deviation from the general trend?

Answer:

1. The general trend of the first ionization enthalpy values of group 13 elements is that they increase as you move down the group.

2. However, this trend is not followed in the case of Al and Ga, as the first ionization enthalpy value of Al is lower than that of Ga.

3. This deviation from the general trend is due to the presence of d-orbitals in the outermost shell of Al and Ga.

4. The d-orbitals are able to hold more electrons than the s-orbitals, and thus, the electrons in the outermost shell of Al and Ga are held more tightly than those in the outermost shell of B, In, and Tl.

5. This makes it more difficult for the electrons in the outermost shell of Al and Ga to be removed, and thus, their first ionization enthalpy values are lower than those of B, In, and Tl.

Question:

How would you react on this statement? Electronegativity of nitrogen (N) on Pauling scale is 3.0 in all the nitrogen compounds.

Answer:

1. I would react to this statement by acknowledging that the statement is correct.

2. I would also point out that the electronegativity of nitrogen on the Pauling scale is actually 3.04, not 3.0.

3. I would also explain that the slight difference in electronegativity is due to the presence of different types of nitrogen compounds, such as nitrogen oxides, nitrides, and nitrogen hydrides.

4. Finally, I would emphasize that the electronegativity of nitrogen is still very close to 3.0, which is why it is often rounded off to 3.0 when discussing the electronegativity of nitrogen in general.

Question:

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 and 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.

Answer:

(a) Boron (B) has five electrons in its outer subshell.

(b) Sodium (Na) would tend to lose two electrons.

(c) Chlorine (Cl) would tend to gain two electrons.

(d) Group 17 (the Halogens) has metal non-metal liquid as well as gas at the room temperature. Chlorine (Cl) is a gas, Bromine (Br) is a liquid, and Fluorine (F) and Astatine (At) are gases.

Question:

The first (ΔiH1) and the second (ΔiH2) ionization enthalpies (in kJ mol−1) and the (ΔegH) electron gain enthalpy (in kJ mol−1) of a few elements are given below: I ΔH1 520, ΔH2 7300, ΔegH-60 II ΔH1 419, ΔH2 3051, ΔegH-48 III ΔH1 1681, ΔH2 3374, ΔegH-328 IV ΔH1 1008, ΔH2 1846, ΔegH-295 V ΔH1 2372, ΔH2 5251, ΔegH+48 VI ΔH1 738, ΔH2 1451, ΔegH-40 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, (d) the least reactive non-metal, (e) the metal which can form a stable binary halide of the formula MX2 (X=halogen) and (f) the metal which can form a predominantly stable covalent halide of the formula MX (X=halogen)?

Answer:

(a) The least reactive element: Element VI (ΔH1 738, ΔH2 1451, ΔegH-40)

(b) The most reactive metal: Element III (ΔH1 1681, ΔH2 3374, ΔegH-328)

(c) The most reactive non-metal: Element V (ΔH1 2372, ΔH2 5251, ΔegH+48)

(d) The least reactive non-metal: Element IV (ΔH1 1008, ΔH2 1846, ΔegH-295)

(e) The metal which can form a stable binary halide of the formula MX2 (X=halogen): Element III (ΔH1 1681, ΔH2 3374, ΔegH-328)

(f) The metal which can form a predominantly stable covalent halide of the formula MX (X=halogen): Element V (ΔH1 2372, ΔH2 5251, ΔegH+48)

Question:

Predict the formulae 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

Answer:

(a) Li2O (b) Mg3N2 (c) Al2I3 (d) SiO2 (e) PF3 (f) Element 71F2

Question:

Which one of the following statements is incorrect in relation to ionisation enthalpy? A : Ionization enthalpy increases for each successive valence shell electron. B : The greatest increase in ionization enthalpy is experienced on removal of electron from core of 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.

Answer:

Answer: B : The greatest increase in ionization enthalpy is experienced on removal of electron from core of noble gas configuration.