Frank Textbook Solutions: Periodic Properties And Variation Of Properties

 Page 1


Chapter 1. Periodic Properties and Variation of 
Properties
PAGE NO : 16 
Solution 1: 
Modern periodic law states that the physical and chemical properties of elements are a 
periodic function of their atomic numbers i.e., if the elements are arranged in the order of 
their atomic numbers, the elements with similar properties are repeated after definite 
regular intervals. 
Concept Insight: The elements are characterized by their atomic number as well as 
atomic weight. Modern periodic law uses atomic number which is number of protons or 
number of electrons present in an atom of an element.
Solution 2: 
Modern periodic table consists of eighteen groups and seven periods. 
Concept Insight: Classification of elements on the basis of increasing atomic number is 
known as Modern Periodic Table. The vertical columns are called groups and the horizontal 
rows are called periods.
Solution 3: 
The recurrence of similar properties of elements after certain regular intervals when they 
are arranged in the order of increasing atomic numbers is called periodicity. 
Concept Insight: Periodicity in properties is due to the repetition of similar outer 
electronic configuration of elements at certain regular intervals.
Solution 4: 
In general, the elements belonging to a group have the same number of valence electrons 
.For example, all the group 1 elements have valency one since they have only one electron 
in their outermost shell. 
In general, the elements belonging to a period do not have same valency but their valence 
shell remains the same. For example, second period has 8 elements with atomic number 3 
to 10 but in all of them the valence electrons are present in shell number two. 
Concept Insight: For elements in a group the number of electrons present in the 
outermost shell is the same and therefore the elements have same valency and or 
elements in a period number of electrons present in the outermost shell of elements in a 
period increase from left to right but the shell does remains the same.
Solution 5: 
Fluorine has lower electron affinity than chlorine because of the small size of fluorine which 
results in stronger repulsion between the electron and the electrons already present in the 
atom of fluorine. Hence the energy released in accepting an electron is lesser in fluorine 
than that of chlorine. 
Concept Insight: For answering this question you should recall that electron affinity is the 
energy released when an electron is added to an isolated gaseous atom to form an anion. 
Due to small size of fluorine atom, the valence shell is already crowded, hence when an 
electron is added to a fluorine atom in gaseous state there occurs strong repulsion between 
the added electron and those already present in the atom hence less amount of energy is
released .
Page 2


Chapter 1. Periodic Properties and Variation of 
Properties
PAGE NO : 16 
Solution 1: 
Modern periodic law states that the physical and chemical properties of elements are a 
periodic function of their atomic numbers i.e., if the elements are arranged in the order of 
their atomic numbers, the elements with similar properties are repeated after definite 
regular intervals. 
Concept Insight: The elements are characterized by their atomic number as well as 
atomic weight. Modern periodic law uses atomic number which is number of protons or 
number of electrons present in an atom of an element.
Solution 2: 
Modern periodic table consists of eighteen groups and seven periods. 
Concept Insight: Classification of elements on the basis of increasing atomic number is 
known as Modern Periodic Table. The vertical columns are called groups and the horizontal 
rows are called periods.
Solution 3: 
The recurrence of similar properties of elements after certain regular intervals when they 
are arranged in the order of increasing atomic numbers is called periodicity. 
Concept Insight: Periodicity in properties is due to the repetition of similar outer 
electronic configuration of elements at certain regular intervals.
Solution 4: 
In general, the elements belonging to a group have the same number of valence electrons 
.For example, all the group 1 elements have valency one since they have only one electron 
in their outermost shell. 
In general, the elements belonging to a period do not have same valency but their valence 
shell remains the same. For example, second period has 8 elements with atomic number 3 
to 10 but in all of them the valence electrons are present in shell number two. 
Concept Insight: For elements in a group the number of electrons present in the 
outermost shell is the same and therefore the elements have same valency and or 
elements in a period number of electrons present in the outermost shell of elements in a 
period increase from left to right but the shell does remains the same.
Solution 5: 
Fluorine has lower electron affinity than chlorine because of the small size of fluorine which 
results in stronger repulsion between the electron and the electrons already present in the 
atom of fluorine. Hence the energy released in accepting an electron is lesser in fluorine 
than that of chlorine. 
Concept Insight: For answering this question you should recall that electron affinity is the 
energy released when an electron is added to an isolated gaseous atom to form an anion. 
Due to small size of fluorine atom, the valence shell is already crowded, hence when an 
electron is added to a fluorine atom in gaseous state there occurs strong repulsion between 
the added electron and those already present in the atom hence less amount of energy is
released .
 Solution 6:
1. The element with highest first ionization energy: Neon (Ne)
2. The element with highest electro negativity: Fluorine (F)
3. The element with largest atomic size: Lithium (Li)
4. The most reactive non-metal: Fluorine
5. The most reactive metal: Lithium
6. Concept Insight:
Neon has highest ionization energy since it is a noble gas and has its octet
 
complete which makes it very stable.
Fluorine has highest electronegativity as we know that electro negativity
 
increases along a period due to decreasing atomic size and increasing nuclear
 
charge.
Lithium has the largest atomic size since it is an alkali metal i.e., belongs to
 
group 1 and we know that as we move from left to right in a period atomic size
 
decreases. So lithium has largest size while fluorine has smallest size in second
 
period.
Fluorine is most reactive non metal as it requires only one electron to complete
 
its octet and become stable.
Lithium is the most reactive metal as it can complete its octet by losing its
 
single electron present in its outermost shell.
PAGE NO : 17
 
Solution 7:
1. The most metallic element will be found at C.
2. The most non-metallic element will be found at D.
Concept Insight: For answering this question you should recall metallic character
 
increases down the group and also increases with the increasing size of the atom. Since
 
elements of group 1 has largest atomic sizes among all the elements of periodic table so
 
the most metallic element belongs to group 1.
 
Similarly, non-metallic character decreases down the group and increases with the
 
decreasing size of atom.
Solution 8:
Page 3


Chapter 1. Periodic Properties and Variation of 
Properties
PAGE NO : 16 
Solution 1: 
Modern periodic law states that the physical and chemical properties of elements are a 
periodic function of their atomic numbers i.e., if the elements are arranged in the order of 
their atomic numbers, the elements with similar properties are repeated after definite 
regular intervals. 
Concept Insight: The elements are characterized by their atomic number as well as 
atomic weight. Modern periodic law uses atomic number which is number of protons or 
number of electrons present in an atom of an element.
Solution 2: 
Modern periodic table consists of eighteen groups and seven periods. 
Concept Insight: Classification of elements on the basis of increasing atomic number is 
known as Modern Periodic Table. The vertical columns are called groups and the horizontal 
rows are called periods.
Solution 3: 
The recurrence of similar properties of elements after certain regular intervals when they 
are arranged in the order of increasing atomic numbers is called periodicity. 
Concept Insight: Periodicity in properties is due to the repetition of similar outer 
electronic configuration of elements at certain regular intervals.
Solution 4: 
In general, the elements belonging to a group have the same number of valence electrons 
.For example, all the group 1 elements have valency one since they have only one electron 
in their outermost shell. 
In general, the elements belonging to a period do not have same valency but their valence 
shell remains the same. For example, second period has 8 elements with atomic number 3 
to 10 but in all of them the valence electrons are present in shell number two. 
Concept Insight: For elements in a group the number of electrons present in the 
outermost shell is the same and therefore the elements have same valency and or 
elements in a period number of electrons present in the outermost shell of elements in a 
period increase from left to right but the shell does remains the same.
Solution 5: 
Fluorine has lower electron affinity than chlorine because of the small size of fluorine which 
results in stronger repulsion between the electron and the electrons already present in the 
atom of fluorine. Hence the energy released in accepting an electron is lesser in fluorine 
than that of chlorine. 
Concept Insight: For answering this question you should recall that electron affinity is the 
energy released when an electron is added to an isolated gaseous atom to form an anion. 
Due to small size of fluorine atom, the valence shell is already crowded, hence when an 
electron is added to a fluorine atom in gaseous state there occurs strong repulsion between 
the added electron and those already present in the atom hence less amount of energy is
released .
 Solution 6:
1. The element with highest first ionization energy: Neon (Ne)
2. The element with highest electro negativity: Fluorine (F)
3. The element with largest atomic size: Lithium (Li)
4. The most reactive non-metal: Fluorine
5. The most reactive metal: Lithium
6. Concept Insight:
Neon has highest ionization energy since it is a noble gas and has its octet
 
complete which makes it very stable.
Fluorine has highest electronegativity as we know that electro negativity
 
increases along a period due to decreasing atomic size and increasing nuclear
 
charge.
Lithium has the largest atomic size since it is an alkali metal i.e., belongs to
 
group 1 and we know that as we move from left to right in a period atomic size
 
decreases. So lithium has largest size while fluorine has smallest size in second
 
period.
Fluorine is most reactive non metal as it requires only one electron to complete
 
its octet and become stable.
Lithium is the most reactive metal as it can complete its octet by losing its
 
single electron present in its outermost shell.
PAGE NO : 17
 
Solution 7:
1. The most metallic element will be found at C.
2. The most non-metallic element will be found at D.
Concept Insight: For answering this question you should recall metallic character
 
increases down the group and also increases with the increasing size of the atom. Since
 
elements of group 1 has largest atomic sizes among all the elements of periodic table so
 
the most metallic element belongs to group 1.
 
Similarly, non-metallic character decreases down the group and increases with the
 
decreasing size of atom.
Solution 8:
 Solution 9:
1. 18, 7.
2. First.
3. Seventeen.
4. Electron affinity.
5. Decrease, increase
6. Fluorine
7. Zero.
Solution 10:
1. False.
2. True.
3. True.
4. True.
5. True.
6. True.
Concept Insight: (i) There is inverse relation between atomic size and electron affinity.
 
More is the size, less is the electron affinity and vice versa because more is the size of
 
atom, more is the distance between the nucleus and last shell to which electron enters.
 
This results in decrease in force of attraction between the nucleus and incoming electron
 
and hence the electron affinity decreases. Fluorine has smaller size than chlorine so it must
 
have less electron affinity than chlorine.
Solution 11:
1. Li < Be < B
2. I < Br < F < Cl
3. SiO2 < P2O5 < SO3 < Cl2O7
4. I+ < I < I-
Concept Insight:
1. Li, Be, B belongs to second period and ionization energy increase as we move left to
right in a period due to increased nuclear charge and decrease of atomic size.
2. Electron affinity decreases down the group due to increase in atomic size as it results
in more distance between nucleus and last shell to which incoming electron enters.
Hence, incoming electron feels less attraction from the nucleus.
3. In a period, acidic nature of oxide increases.
4. Size of a cation is always smaller than the corresponding atom due to decrease in
number of electrons and increase in effective nuclear charge i.e., greater force of
attraction by the nucleus on the electrons.
Size of an anion is always more than the corresponding atom due to decrease in
effective nuclear charge i.e., lesser force of attraction by the nucleus o the electrons.
Page 4


Chapter 1. Periodic Properties and Variation of 
Properties
PAGE NO : 16 
Solution 1: 
Modern periodic law states that the physical and chemical properties of elements are a 
periodic function of their atomic numbers i.e., if the elements are arranged in the order of 
their atomic numbers, the elements with similar properties are repeated after definite 
regular intervals. 
Concept Insight: The elements are characterized by their atomic number as well as 
atomic weight. Modern periodic law uses atomic number which is number of protons or 
number of electrons present in an atom of an element.
Solution 2: 
Modern periodic table consists of eighteen groups and seven periods. 
Concept Insight: Classification of elements on the basis of increasing atomic number is 
known as Modern Periodic Table. The vertical columns are called groups and the horizontal 
rows are called periods.
Solution 3: 
The recurrence of similar properties of elements after certain regular intervals when they 
are arranged in the order of increasing atomic numbers is called periodicity. 
Concept Insight: Periodicity in properties is due to the repetition of similar outer 
electronic configuration of elements at certain regular intervals.
Solution 4: 
In general, the elements belonging to a group have the same number of valence electrons 
.For example, all the group 1 elements have valency one since they have only one electron 
in their outermost shell. 
In general, the elements belonging to a period do not have same valency but their valence 
shell remains the same. For example, second period has 8 elements with atomic number 3 
to 10 but in all of them the valence electrons are present in shell number two. 
Concept Insight: For elements in a group the number of electrons present in the 
outermost shell is the same and therefore the elements have same valency and or 
elements in a period number of electrons present in the outermost shell of elements in a 
period increase from left to right but the shell does remains the same.
Solution 5: 
Fluorine has lower electron affinity than chlorine because of the small size of fluorine which 
results in stronger repulsion between the electron and the electrons already present in the 
atom of fluorine. Hence the energy released in accepting an electron is lesser in fluorine 
than that of chlorine. 
Concept Insight: For answering this question you should recall that electron affinity is the 
energy released when an electron is added to an isolated gaseous atom to form an anion. 
Due to small size of fluorine atom, the valence shell is already crowded, hence when an 
electron is added to a fluorine atom in gaseous state there occurs strong repulsion between 
the added electron and those already present in the atom hence less amount of energy is
released .
 Solution 6:
1. The element with highest first ionization energy: Neon (Ne)
2. The element with highest electro negativity: Fluorine (F)
3. The element with largest atomic size: Lithium (Li)
4. The most reactive non-metal: Fluorine
5. The most reactive metal: Lithium
6. Concept Insight:
Neon has highest ionization energy since it is a noble gas and has its octet
 
complete which makes it very stable.
Fluorine has highest electronegativity as we know that electro negativity
 
increases along a period due to decreasing atomic size and increasing nuclear
 
charge.
Lithium has the largest atomic size since it is an alkali metal i.e., belongs to
 
group 1 and we know that as we move from left to right in a period atomic size
 
decreases. So lithium has largest size while fluorine has smallest size in second
 
period.
Fluorine is most reactive non metal as it requires only one electron to complete
 
its octet and become stable.
Lithium is the most reactive metal as it can complete its octet by losing its
 
single electron present in its outermost shell.
PAGE NO : 17
 
Solution 7:
1. The most metallic element will be found at C.
2. The most non-metallic element will be found at D.
Concept Insight: For answering this question you should recall metallic character
 
increases down the group and also increases with the increasing size of the atom. Since
 
elements of group 1 has largest atomic sizes among all the elements of periodic table so
 
the most metallic element belongs to group 1.
 
Similarly, non-metallic character decreases down the group and increases with the
 
decreasing size of atom.
Solution 8:
 Solution 9:
1. 18, 7.
2. First.
3. Seventeen.
4. Electron affinity.
5. Decrease, increase
6. Fluorine
7. Zero.
Solution 10:
1. False.
2. True.
3. True.
4. True.
5. True.
6. True.
Concept Insight: (i) There is inverse relation between atomic size and electron affinity.
 
More is the size, less is the electron affinity and vice versa because more is the size of
 
atom, more is the distance between the nucleus and last shell to which electron enters.
 
This results in decrease in force of attraction between the nucleus and incoming electron
 
and hence the electron affinity decreases. Fluorine has smaller size than chlorine so it must
 
have less electron affinity than chlorine.
Solution 11:
1. Li < Be < B
2. I < Br < F < Cl
3. SiO2 < P2O5 < SO3 < Cl2O7
4. I+ < I < I-
Concept Insight:
1. Li, Be, B belongs to second period and ionization energy increase as we move left to
right in a period due to increased nuclear charge and decrease of atomic size.
2. Electron affinity decreases down the group due to increase in atomic size as it results
in more distance between nucleus and last shell to which incoming electron enters.
Hence, incoming electron feels less attraction from the nucleus.
3. In a period, acidic nature of oxide increases.
4. Size of a cation is always smaller than the corresponding atom due to decrease in
number of electrons and increase in effective nuclear charge i.e., greater force of
attraction by the nucleus on the electrons.
Size of an anion is always more than the corresponding atom due to decrease in
effective nuclear charge i.e., lesser force of attraction by the nucleus o the electrons.
 
 
 
 
 
 
 
Solution 12:
 
The statement that in each period, the atomic size gradually decreases with increase in
 
atomic number means that as move from left to right in a period, nuclear charge increases
 
by one unit in each succeeding element while the number of shells remains the same. Due
 
to this increased nuclear charge, the electrons of all the shells are pulled closer to the
 
nucleus thereby bringing the outer most shell closer to the nucleus. With the result, the
 
atomic size decreases across a period.
 
For example, in the second period from lithium to fluorine, lithium has the largest size
 
while fluorine has the smallest size.
Solution 13:
 
In the case of noble gases or inert gases there are exceptions and the atomic radius or size
 
of the elements are greater than the other elements of the period to which these elements
 
belong.
PAGE NO : 18
 
Solution 14:
 
As we move down a group, the atomic radii increase because a new shell is added at each
 
succeeding element though the number of electrons in the outer most shell remains the
 
same. Thus, the atomic size of elements increases in size downward.
 
Although nuclear charge also increases in going down the group but the effect of nuclear
 
charge on atomic size is much less than the increase due to addition of a new shell.
 
In group 17, the atomic size follows the trend:
 
F < Cl < Br < I
Solution 15:
 
The elements of third period are:
 
Na, Mg, Al, Si, P, S, Cl, Ar
 
The most metallic element is sodium i.e., Na and the most non-metallic element is chlorine
 
i.e., Cl.
 
Concept Insight:
 
In a period, metallic character decreases on moving from left to right because of decrease
 
in size of atom due to which elements cannot lose electron easily.
Solution 16:
Page 5


Chapter 1. Periodic Properties and Variation of 
Properties
PAGE NO : 16 
Solution 1: 
Modern periodic law states that the physical and chemical properties of elements are a 
periodic function of their atomic numbers i.e., if the elements are arranged in the order of 
their atomic numbers, the elements with similar properties are repeated after definite 
regular intervals. 
Concept Insight: The elements are characterized by their atomic number as well as 
atomic weight. Modern periodic law uses atomic number which is number of protons or 
number of electrons present in an atom of an element.
Solution 2: 
Modern periodic table consists of eighteen groups and seven periods. 
Concept Insight: Classification of elements on the basis of increasing atomic number is 
known as Modern Periodic Table. The vertical columns are called groups and the horizontal 
rows are called periods.
Solution 3: 
The recurrence of similar properties of elements after certain regular intervals when they 
are arranged in the order of increasing atomic numbers is called periodicity. 
Concept Insight: Periodicity in properties is due to the repetition of similar outer 
electronic configuration of elements at certain regular intervals.
Solution 4: 
In general, the elements belonging to a group have the same number of valence electrons 
.For example, all the group 1 elements have valency one since they have only one electron 
in their outermost shell. 
In general, the elements belonging to a period do not have same valency but their valence 
shell remains the same. For example, second period has 8 elements with atomic number 3 
to 10 but in all of them the valence electrons are present in shell number two. 
Concept Insight: For elements in a group the number of electrons present in the 
outermost shell is the same and therefore the elements have same valency and or 
elements in a period number of electrons present in the outermost shell of elements in a 
period increase from left to right but the shell does remains the same.
Solution 5: 
Fluorine has lower electron affinity than chlorine because of the small size of fluorine which 
results in stronger repulsion between the electron and the electrons already present in the 
atom of fluorine. Hence the energy released in accepting an electron is lesser in fluorine 
than that of chlorine. 
Concept Insight: For answering this question you should recall that electron affinity is the 
energy released when an electron is added to an isolated gaseous atom to form an anion. 
Due to small size of fluorine atom, the valence shell is already crowded, hence when an 
electron is added to a fluorine atom in gaseous state there occurs strong repulsion between 
the added electron and those already present in the atom hence less amount of energy is
released .
 Solution 6:
1. The element with highest first ionization energy: Neon (Ne)
2. The element with highest electro negativity: Fluorine (F)
3. The element with largest atomic size: Lithium (Li)
4. The most reactive non-metal: Fluorine
5. The most reactive metal: Lithium
6. Concept Insight:
Neon has highest ionization energy since it is a noble gas and has its octet
 
complete which makes it very stable.
Fluorine has highest electronegativity as we know that electro negativity
 
increases along a period due to decreasing atomic size and increasing nuclear
 
charge.
Lithium has the largest atomic size since it is an alkali metal i.e., belongs to
 
group 1 and we know that as we move from left to right in a period atomic size
 
decreases. So lithium has largest size while fluorine has smallest size in second
 
period.
Fluorine is most reactive non metal as it requires only one electron to complete
 
its octet and become stable.
Lithium is the most reactive metal as it can complete its octet by losing its
 
single electron present in its outermost shell.
PAGE NO : 17
 
Solution 7:
1. The most metallic element will be found at C.
2. The most non-metallic element will be found at D.
Concept Insight: For answering this question you should recall metallic character
 
increases down the group and also increases with the increasing size of the atom. Since
 
elements of group 1 has largest atomic sizes among all the elements of periodic table so
 
the most metallic element belongs to group 1.
 
Similarly, non-metallic character decreases down the group and increases with the
 
decreasing size of atom.
Solution 8:
 Solution 9:
1. 18, 7.
2. First.
3. Seventeen.
4. Electron affinity.
5. Decrease, increase
6. Fluorine
7. Zero.
Solution 10:
1. False.
2. True.
3. True.
4. True.
5. True.
6. True.
Concept Insight: (i) There is inverse relation between atomic size and electron affinity.
 
More is the size, less is the electron affinity and vice versa because more is the size of
 
atom, more is the distance between the nucleus and last shell to which electron enters.
 
This results in decrease in force of attraction between the nucleus and incoming electron
 
and hence the electron affinity decreases. Fluorine has smaller size than chlorine so it must
 
have less electron affinity than chlorine.
Solution 11:
1. Li < Be < B
2. I < Br < F < Cl
3. SiO2 < P2O5 < SO3 < Cl2O7
4. I+ < I < I-
Concept Insight:
1. Li, Be, B belongs to second period and ionization energy increase as we move left to
right in a period due to increased nuclear charge and decrease of atomic size.
2. Electron affinity decreases down the group due to increase in atomic size as it results
in more distance between nucleus and last shell to which incoming electron enters.
Hence, incoming electron feels less attraction from the nucleus.
3. In a period, acidic nature of oxide increases.
4. Size of a cation is always smaller than the corresponding atom due to decrease in
number of electrons and increase in effective nuclear charge i.e., greater force of
attraction by the nucleus on the electrons.
Size of an anion is always more than the corresponding atom due to decrease in
effective nuclear charge i.e., lesser force of attraction by the nucleus o the electrons.
 
 
 
 
 
 
 
Solution 12:
 
The statement that in each period, the atomic size gradually decreases with increase in
 
atomic number means that as move from left to right in a period, nuclear charge increases
 
by one unit in each succeeding element while the number of shells remains the same. Due
 
to this increased nuclear charge, the electrons of all the shells are pulled closer to the
 
nucleus thereby bringing the outer most shell closer to the nucleus. With the result, the
 
atomic size decreases across a period.
 
For example, in the second period from lithium to fluorine, lithium has the largest size
 
while fluorine has the smallest size.
Solution 13:
 
In the case of noble gases or inert gases there are exceptions and the atomic radius or size
 
of the elements are greater than the other elements of the period to which these elements
 
belong.
PAGE NO : 18
 
Solution 14:
 
As we move down a group, the atomic radii increase because a new shell is added at each
 
succeeding element though the number of electrons in the outer most shell remains the
 
same. Thus, the atomic size of elements increases in size downward.
 
Although nuclear charge also increases in going down the group but the effect of nuclear
 
charge on atomic size is much less than the increase due to addition of a new shell.
 
In group 17, the atomic size follows the trend:
 
F < Cl < Br < I
Solution 15:
 
The elements of third period are:
 
Na, Mg, Al, Si, P, S, Cl, Ar
 
The most metallic element is sodium i.e., Na and the most non-metallic element is chlorine
 
i.e., Cl.
 
Concept Insight:
 
In a period, metallic character decreases on moving from left to right because of decrease
 
in size of atom due to which elements cannot lose electron easily.
Solution 16:
 Solution 17:
 
Solution 18:
 
Electron affinity is the energy released when an electron is added to an isolated gaseous
 
atom to form the negative ion (anion).
 
Unit: Its units are electron volt (eV).
 
Its SI units are Kilojoules per mole(KJmol)
-1
Solution 19:
 
Out of A and B, A will ionize more easily to form a negative anion because of the high value
 
of electron affinity, energy released during addition of electron will be high hence the
 
resulting anion formed will be more stable than the corresponding atom.
Solution 20:
1. Larger the atomic size, farther is the valence electron from the nucleus and lesser is
 
the pull exerted on it. As a result, electron can be easily removed from the valence
 
shell and hence more metallic is the element.
2. Halogens need only one electron to complete their octet and become stable their
 
atomic size is very less hence the distance between their last shell and nucleus is
 
very less, as a result the force of attraction between the nucleus and the incoming
electron is less and hence the electron affinity is high for halogens.
3. When an atom loses or gain electron to form ion, the number of electrons present in
the outermost shell also changes. Corresponding to that effective nuclear charge on
the changed number of electrons also change which further changes the size of an
atom as there is inverse relation between effective nuclear charge and size of atom.
4. K and Li belongs to group 1 i.e., metals and we know that for metals chemical
reactivity of elements increases down the group because chemical reactivity
increases as electropositive or metallic character increases.