Selina Textbook Solutions: Periodic Table - Periodic Properties and Variations of Properties | Chemistry Class 10 ICSE PDF Download

 Page 1


Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
      
INTEXT - QUESTION  - 1 
  
Question 1: 
a) State modern periodic law. Name the scientist who stated the law. 
b) What is a periodic table? How many groups and periods does modern periodic table have? 
Solution 1: 
a) The modern periodic law states that "The properties of elements are the periodic functions 
of their atomic number." Henry Moseley put forward the modern periodic law. 
b) A tabular arrangement of the elements in groups (vertical columns) and periods (horizontal 
rows) highlighting the regular trends in properties of elements is called a Periodic Table. 
Modern Periodic table has 7 periods and 18 groups. 
 
 
Question 2: 
Why sodium element of group 1 and chlorine element of group 17 both have valency 1?  
Solution 2: 
Valency is the combining capacity of the atom of an element. It is equal to the number of 
electrons an atom can donate or accept or share. It is just a number and does not have a positive 
or negative sign. 
Group 1 elements have 1 electron in their outermost orbital, while Group 7 elements have 7 
electrons in their outermost orbital. 
Valency depends on the number of electrons in the outermost shell (i.e. valence shell). 
If the number of electrons present in the outermost shell is 1, then it can donate one electron 
while combining with other elements to obtain a stable electronic configuration. 
If the number of electrons present in the outermost shell is 7, then its valency is again 1 (8 - 7 = 
1) as it can accept 1 electron from the combining atom. 
In a given period, the number of electrons in the valence (outermost) shell increases from left to 
right. But the valency increases only up to Group 14, where it becomes 4, and then it decreases, 
that is, it becomes 1 in Group 17. 
 
 
Question 3: 
What are horizontal rows and vertical columns in a periodic table known as?  
Solution 3: 
The horizontal rows are known as periods and vertical columns in the periodic table are known 
as groups 
 
 
 
 
Page 2


Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
      
INTEXT - QUESTION  - 1 
  
Question 1: 
a) State modern periodic law. Name the scientist who stated the law. 
b) What is a periodic table? How many groups and periods does modern periodic table have? 
Solution 1: 
a) The modern periodic law states that "The properties of elements are the periodic functions 
of their atomic number." Henry Moseley put forward the modern periodic law. 
b) A tabular arrangement of the elements in groups (vertical columns) and periods (horizontal 
rows) highlighting the regular trends in properties of elements is called a Periodic Table. 
Modern Periodic table has 7 periods and 18 groups. 
 
 
Question 2: 
Why sodium element of group 1 and chlorine element of group 17 both have valency 1?  
Solution 2: 
Valency is the combining capacity of the atom of an element. It is equal to the number of 
electrons an atom can donate or accept or share. It is just a number and does not have a positive 
or negative sign. 
Group 1 elements have 1 electron in their outermost orbital, while Group 7 elements have 7 
electrons in their outermost orbital. 
Valency depends on the number of electrons in the outermost shell (i.e. valence shell). 
If the number of electrons present in the outermost shell is 1, then it can donate one electron 
while combining with other elements to obtain a stable electronic configuration. 
If the number of electrons present in the outermost shell is 7, then its valency is again 1 (8 - 7 = 
1) as it can accept 1 electron from the combining atom. 
In a given period, the number of electrons in the valence (outermost) shell increases from left to 
right. But the valency increases only up to Group 14, where it becomes 4, and then it decreases, 
that is, it becomes 1 in Group 17. 
 
 
Question 3: 
What are horizontal rows and vertical columns in a periodic table known as?  
Solution 3: 
The horizontal rows are known as periods and vertical columns in the periodic table are known 
as groups 
 
 
 
 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
Question 4: 
Periodicity is observed due to the similar …………………. 
(Number of valence electrons / atomic number / electronic configuration). 
Solution 4:  
Periodicity is observed due to the similar electronic configuration. 
(Number of valence electrons / atomic number / electronic configuration). 
 
 
Question 5: 
How does the electronic configuration in atoms change 
(i) in a period from left to right?  
(ii)  in a group top to bottom? 
Solution 5: 
(i) Though the number of shells remain the same, number of valence electrons increases by one, 
as we move across any given period from left to right. 
(ii) While going from top to bottom in a group, the number of shells increases successively i.e. 
one by one but the number of valence electrons remains the same. 
 
 
Question 6: 
Correct the statements. 
(i) Elements in the same periods have equal valency.  
(ii) Valency depends upon the number of shells in an atom. 
(iii) Copper and zinc are representative elements.  
(iv) Transition elements are placed at extreme right of the periodic table. 
Solution 6: 
(i) Elements in the same group have equal valency. 
(ii) Valency depends upon the number of valence electrons in an atom. 
(iii) Copper and zinc are transition elements. 
(iv) Noble gases are placed at the extreme right of the periodic table. 
 
 
Question 7: 
Name two elements in each case: 
(i) Alkali metals  
(ii) Akaline earth metals   
(iii) halogens  
(iv) Inert gas  
(v) Transition element  
Page 3


Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
      
INTEXT - QUESTION  - 1 
  
Question 1: 
a) State modern periodic law. Name the scientist who stated the law. 
b) What is a periodic table? How many groups and periods does modern periodic table have? 
Solution 1: 
a) The modern periodic law states that "The properties of elements are the periodic functions 
of their atomic number." Henry Moseley put forward the modern periodic law. 
b) A tabular arrangement of the elements in groups (vertical columns) and periods (horizontal 
rows) highlighting the regular trends in properties of elements is called a Periodic Table. 
Modern Periodic table has 7 periods and 18 groups. 
 
 
Question 2: 
Why sodium element of group 1 and chlorine element of group 17 both have valency 1?  
Solution 2: 
Valency is the combining capacity of the atom of an element. It is equal to the number of 
electrons an atom can donate or accept or share. It is just a number and does not have a positive 
or negative sign. 
Group 1 elements have 1 electron in their outermost orbital, while Group 7 elements have 7 
electrons in their outermost orbital. 
Valency depends on the number of electrons in the outermost shell (i.e. valence shell). 
If the number of electrons present in the outermost shell is 1, then it can donate one electron 
while combining with other elements to obtain a stable electronic configuration. 
If the number of electrons present in the outermost shell is 7, then its valency is again 1 (8 - 7 = 
1) as it can accept 1 electron from the combining atom. 
In a given period, the number of electrons in the valence (outermost) shell increases from left to 
right. But the valency increases only up to Group 14, where it becomes 4, and then it decreases, 
that is, it becomes 1 in Group 17. 
 
 
Question 3: 
What are horizontal rows and vertical columns in a periodic table known as?  
Solution 3: 
The horizontal rows are known as periods and vertical columns in the periodic table are known 
as groups 
 
 
 
 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
Question 4: 
Periodicity is observed due to the similar …………………. 
(Number of valence electrons / atomic number / electronic configuration). 
Solution 4:  
Periodicity is observed due to the similar electronic configuration. 
(Number of valence electrons / atomic number / electronic configuration). 
 
 
Question 5: 
How does the electronic configuration in atoms change 
(i) in a period from left to right?  
(ii)  in a group top to bottom? 
Solution 5: 
(i) Though the number of shells remain the same, number of valence electrons increases by one, 
as we move across any given period from left to right. 
(ii) While going from top to bottom in a group, the number of shells increases successively i.e. 
one by one but the number of valence electrons remains the same. 
 
 
Question 6: 
Correct the statements. 
(i) Elements in the same periods have equal valency.  
(ii) Valency depends upon the number of shells in an atom. 
(iii) Copper and zinc are representative elements.  
(iv) Transition elements are placed at extreme right of the periodic table. 
Solution 6: 
(i) Elements in the same group have equal valency. 
(ii) Valency depends upon the number of valence electrons in an atom. 
(iii) Copper and zinc are transition elements. 
(iv) Noble gases are placed at the extreme right of the periodic table. 
 
 
Question 7: 
Name two elements in each case: 
(i) Alkali metals  
(ii) Akaline earth metals   
(iii) halogens  
(iv) Inert gas  
(v) Transition element  
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
(vi) Lanthanides  
(vii) Actinides  
Solution 7: 
(i) Alkali metals Sodium and potassium 
(ii) Akaline earth metals  Calcium and magnesium  
(iii) halogens Chlorine and bromine  
(iv) Inert gas Neon and Argon 
(v) Transition element Iron and Cobalt 
(vi) Lanthanides Cerium and Europium  
(vii) Actinides Uranium and Neptunium  
 
 
Question 8: 
What do you understand by? 
(i) Periodicity:    
(ii) Typical elements:  
(iii)  Orbits:  
Solution 8: 
(i) The properties that reappear at regular intervals, or in which there is a gradual variation at 
regular intervals, are called periodic properties and the phenomenon is known as the 
periodicity of elements. 
(ii) The third period elements, Na, Mg, Al, Si, P and Cl summarize the properties of their 
respective groups and are called typical elements. 
(iii) The elements of the second period show resemblance in properties with the elements of the 
next group of the third period leading to a diagonal relationship. Such elements are called 
bridge elements. 
 
 
Question 9: 
Why are noble gases placed in a separate group? 
Solution 9: 
Noble gases are unreactive since they have their outermost orbit complete. Due to stable 
electronic configuration they hardly react with other elements. So these elements are placed in 
a separate group i.e.18 
 
 
Question 10: 
Name two elements you would expect to show chemical reactions similar to calcium. What is 
the basis of your choice? 
Solution 10: 
Page 4


Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
      
INTEXT - QUESTION  - 1 
  
Question 1: 
a) State modern periodic law. Name the scientist who stated the law. 
b) What is a periodic table? How many groups and periods does modern periodic table have? 
Solution 1: 
a) The modern periodic law states that "The properties of elements are the periodic functions 
of their atomic number." Henry Moseley put forward the modern periodic law. 
b) A tabular arrangement of the elements in groups (vertical columns) and periods (horizontal 
rows) highlighting the regular trends in properties of elements is called a Periodic Table. 
Modern Periodic table has 7 periods and 18 groups. 
 
 
Question 2: 
Why sodium element of group 1 and chlorine element of group 17 both have valency 1?  
Solution 2: 
Valency is the combining capacity of the atom of an element. It is equal to the number of 
electrons an atom can donate or accept or share. It is just a number and does not have a positive 
or negative sign. 
Group 1 elements have 1 electron in their outermost orbital, while Group 7 elements have 7 
electrons in their outermost orbital. 
Valency depends on the number of electrons in the outermost shell (i.e. valence shell). 
If the number of electrons present in the outermost shell is 1, then it can donate one electron 
while combining with other elements to obtain a stable electronic configuration. 
If the number of electrons present in the outermost shell is 7, then its valency is again 1 (8 - 7 = 
1) as it can accept 1 electron from the combining atom. 
In a given period, the number of electrons in the valence (outermost) shell increases from left to 
right. But the valency increases only up to Group 14, where it becomes 4, and then it decreases, 
that is, it becomes 1 in Group 17. 
 
 
Question 3: 
What are horizontal rows and vertical columns in a periodic table known as?  
Solution 3: 
The horizontal rows are known as periods and vertical columns in the periodic table are known 
as groups 
 
 
 
 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
Question 4: 
Periodicity is observed due to the similar …………………. 
(Number of valence electrons / atomic number / electronic configuration). 
Solution 4:  
Periodicity is observed due to the similar electronic configuration. 
(Number of valence electrons / atomic number / electronic configuration). 
 
 
Question 5: 
How does the electronic configuration in atoms change 
(i) in a period from left to right?  
(ii)  in a group top to bottom? 
Solution 5: 
(i) Though the number of shells remain the same, number of valence electrons increases by one, 
as we move across any given period from left to right. 
(ii) While going from top to bottom in a group, the number of shells increases successively i.e. 
one by one but the number of valence electrons remains the same. 
 
 
Question 6: 
Correct the statements. 
(i) Elements in the same periods have equal valency.  
(ii) Valency depends upon the number of shells in an atom. 
(iii) Copper and zinc are representative elements.  
(iv) Transition elements are placed at extreme right of the periodic table. 
Solution 6: 
(i) Elements in the same group have equal valency. 
(ii) Valency depends upon the number of valence electrons in an atom. 
(iii) Copper and zinc are transition elements. 
(iv) Noble gases are placed at the extreme right of the periodic table. 
 
 
Question 7: 
Name two elements in each case: 
(i) Alkali metals  
(ii) Akaline earth metals   
(iii) halogens  
(iv) Inert gas  
(v) Transition element  
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
(vi) Lanthanides  
(vii) Actinides  
Solution 7: 
(i) Alkali metals Sodium and potassium 
(ii) Akaline earth metals  Calcium and magnesium  
(iii) halogens Chlorine and bromine  
(iv) Inert gas Neon and Argon 
(v) Transition element Iron and Cobalt 
(vi) Lanthanides Cerium and Europium  
(vii) Actinides Uranium and Neptunium  
 
 
Question 8: 
What do you understand by? 
(i) Periodicity:    
(ii) Typical elements:  
(iii)  Orbits:  
Solution 8: 
(i) The properties that reappear at regular intervals, or in which there is a gradual variation at 
regular intervals, are called periodic properties and the phenomenon is known as the 
periodicity of elements. 
(ii) The third period elements, Na, Mg, Al, Si, P and Cl summarize the properties of their 
respective groups and are called typical elements. 
(iii) The elements of the second period show resemblance in properties with the elements of the 
next group of the third period leading to a diagonal relationship. Such elements are called 
bridge elements. 
 
 
Question 9: 
Why are noble gases placed in a separate group? 
Solution 9: 
Noble gases are unreactive since they have their outermost orbit complete. Due to stable 
electronic configuration they hardly react with other elements. So these elements are placed in 
a separate group i.e.18 
 
 
Question 10: 
Name two elements you would expect to show chemical reactions similar to calcium. What is 
the basis of your choice? 
Solution 10: 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
Beryllium and magnesium will show similar chemical reactions as calcium. Since these 
elements belong to same group 2 and also have two electrons in their outermost shell like 
calcium. 
 
 
Question 11: 
Name the metal(s) and non-metals in the first twenty elements.  
Metals:  
Non-metals:  
Solution 11: 
Metals: Lithium, Beryllium, Sodium, Magnesium, Aluminium, Potassium, Calcium. 
Non-metals: Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Fluorine, Neon, 
Phosphorus, Sulphur, Chlorine, Argon. 
 
 
Question 12: 
Name the type of elements, which have their: 
(i) Outermost shell complete – .................... 
(ii) Outermost shell incomplete – ……………… 
(iii) two outermost shell incomplete – ……………… 
(iv)one electron short of octet – …………………… 
(v) two electrons in the outermost orbit - …………… 
Solution 12: 
(i) Outermost shell complete – Noble gases 
(ii) Outermost shell incomplete – Representative elements 
(iii) two outermost shell incomplete – Transition elements 
(iv)one electron short of octet – Halogens 
(v) two electrons in the outermost orbit - Alkaline Earth metals 
 
 
Question 13: 
An element has 2 electrons in its N shell. 
(i) What is its atomic number?  
(ii) State its position in periodic table 
(iii) Is is metal or non-metal? 
(iv) State the name assigned to this group? 
 
Solution 13: 
Page 5


Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
      
INTEXT - QUESTION  - 1 
  
Question 1: 
a) State modern periodic law. Name the scientist who stated the law. 
b) What is a periodic table? How many groups and periods does modern periodic table have? 
Solution 1: 
a) The modern periodic law states that "The properties of elements are the periodic functions 
of their atomic number." Henry Moseley put forward the modern periodic law. 
b) A tabular arrangement of the elements in groups (vertical columns) and periods (horizontal 
rows) highlighting the regular trends in properties of elements is called a Periodic Table. 
Modern Periodic table has 7 periods and 18 groups. 
 
 
Question 2: 
Why sodium element of group 1 and chlorine element of group 17 both have valency 1?  
Solution 2: 
Valency is the combining capacity of the atom of an element. It is equal to the number of 
electrons an atom can donate or accept or share. It is just a number and does not have a positive 
or negative sign. 
Group 1 elements have 1 electron in their outermost orbital, while Group 7 elements have 7 
electrons in their outermost orbital. 
Valency depends on the number of electrons in the outermost shell (i.e. valence shell). 
If the number of electrons present in the outermost shell is 1, then it can donate one electron 
while combining with other elements to obtain a stable electronic configuration. 
If the number of electrons present in the outermost shell is 7, then its valency is again 1 (8 - 7 = 
1) as it can accept 1 electron from the combining atom. 
In a given period, the number of electrons in the valence (outermost) shell increases from left to 
right. But the valency increases only up to Group 14, where it becomes 4, and then it decreases, 
that is, it becomes 1 in Group 17. 
 
 
Question 3: 
What are horizontal rows and vertical columns in a periodic table known as?  
Solution 3: 
The horizontal rows are known as periods and vertical columns in the periodic table are known 
as groups 
 
 
 
 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
Question 4: 
Periodicity is observed due to the similar …………………. 
(Number of valence electrons / atomic number / electronic configuration). 
Solution 4:  
Periodicity is observed due to the similar electronic configuration. 
(Number of valence electrons / atomic number / electronic configuration). 
 
 
Question 5: 
How does the electronic configuration in atoms change 
(i) in a period from left to right?  
(ii)  in a group top to bottom? 
Solution 5: 
(i) Though the number of shells remain the same, number of valence electrons increases by one, 
as we move across any given period from left to right. 
(ii) While going from top to bottom in a group, the number of shells increases successively i.e. 
one by one but the number of valence electrons remains the same. 
 
 
Question 6: 
Correct the statements. 
(i) Elements in the same periods have equal valency.  
(ii) Valency depends upon the number of shells in an atom. 
(iii) Copper and zinc are representative elements.  
(iv) Transition elements are placed at extreme right of the periodic table. 
Solution 6: 
(i) Elements in the same group have equal valency. 
(ii) Valency depends upon the number of valence electrons in an atom. 
(iii) Copper and zinc are transition elements. 
(iv) Noble gases are placed at the extreme right of the periodic table. 
 
 
Question 7: 
Name two elements in each case: 
(i) Alkali metals  
(ii) Akaline earth metals   
(iii) halogens  
(iv) Inert gas  
(v) Transition element  
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
(vi) Lanthanides  
(vii) Actinides  
Solution 7: 
(i) Alkali metals Sodium and potassium 
(ii) Akaline earth metals  Calcium and magnesium  
(iii) halogens Chlorine and bromine  
(iv) Inert gas Neon and Argon 
(v) Transition element Iron and Cobalt 
(vi) Lanthanides Cerium and Europium  
(vii) Actinides Uranium and Neptunium  
 
 
Question 8: 
What do you understand by? 
(i) Periodicity:    
(ii) Typical elements:  
(iii)  Orbits:  
Solution 8: 
(i) The properties that reappear at regular intervals, or in which there is a gradual variation at 
regular intervals, are called periodic properties and the phenomenon is known as the 
periodicity of elements. 
(ii) The third period elements, Na, Mg, Al, Si, P and Cl summarize the properties of their 
respective groups and are called typical elements. 
(iii) The elements of the second period show resemblance in properties with the elements of the 
next group of the third period leading to a diagonal relationship. Such elements are called 
bridge elements. 
 
 
Question 9: 
Why are noble gases placed in a separate group? 
Solution 9: 
Noble gases are unreactive since they have their outermost orbit complete. Due to stable 
electronic configuration they hardly react with other elements. So these elements are placed in 
a separate group i.e.18 
 
 
Question 10: 
Name two elements you would expect to show chemical reactions similar to calcium. What is 
the basis of your choice? 
Solution 10: 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
Beryllium and magnesium will show similar chemical reactions as calcium. Since these 
elements belong to same group 2 and also have two electrons in their outermost shell like 
calcium. 
 
 
Question 11: 
Name the metal(s) and non-metals in the first twenty elements.  
Metals:  
Non-metals:  
Solution 11: 
Metals: Lithium, Beryllium, Sodium, Magnesium, Aluminium, Potassium, Calcium. 
Non-metals: Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Fluorine, Neon, 
Phosphorus, Sulphur, Chlorine, Argon. 
 
 
Question 12: 
Name the type of elements, which have their: 
(i) Outermost shell complete – .................... 
(ii) Outermost shell incomplete – ……………… 
(iii) two outermost shell incomplete – ……………… 
(iv)one electron short of octet – …………………… 
(v) two electrons in the outermost orbit - …………… 
Solution 12: 
(i) Outermost shell complete – Noble gases 
(ii) Outermost shell incomplete – Representative elements 
(iii) two outermost shell incomplete – Transition elements 
(iv)one electron short of octet – Halogens 
(v) two electrons in the outermost orbit - Alkaline Earth metals 
 
 
Question 13: 
An element has 2 electrons in its N shell. 
(i) What is its atomic number?  
(ii) State its position in periodic table 
(iii) Is is metal or non-metal? 
(iv) State the name assigned to this group? 
 
Solution 13: 
Class X Chapter 1 – Periodic Table Chemistry 
______________________________________________________________________________ 
 
(i) 30  
(ii) It belongs to group 12 and fourth period. 
(iii) It is a metal. 
(iv) The name assigned to this group is IIB 
 
 
Question 14: 
State the valency of the elements of periods 3 and write the formula of their oxides. 
Solution 14: 
Elements Valency Formula of oxides 
Na 1 Na
2
O 
Mg 2 MgO 
Al 3 Al2O3 
Si 4 SiO2 
P 5 P2O5 
S 2 SO2 
CI 1 Cl2O 
 
 
Question 15: 
An element A has atomic number 14. To which period does this element belong and how 
many elements are there in this period. 
Solution 15: 
An element A with atomic number 14 belongs to period three and there are eight elements 
in this period. 
 
 
Question 16: 
Answer the following in respect of element 
????
????
 ?? 
(i) Give its electronic configuration 
(ii) To which group and period does it belong? 
(iii) What is its valency? 
(iv) Is it a metal or non - metal 
(v) Is it a reducing agent or oxidizing agent? 
(vi) Give its formula with chlorine. 
Solution 16: 
(i) Electronic configuration of P: 2, 8, 5 
(ii) 15
th
 Group and 3
rd
 Period. 
(iii)Valency of P = 8 - 5 = 3