In the previous section 3.2, we saw this:
• All elements belonging to a group will have:
♦ Same 'valence electrons'
♦ Similar 'valence orbitals'
♦ Similar 'physical and chemical properties'
■ In this section, we will see the various blocks in the periodic table
1. The elements of the periodic table are classified into four blocks:
s-block, p-block, d-block and f-block
2. How did the blocks get those names?
Answer:
(i) Consider any element in the s-block
• The last electron in that element will be present in an s orbital
(ii) Consider any element in the p-block
• The last electron in that element will be present in an p orbital
(iii) Consider any element in the d-block
• The last electron in that element will be present in an d orbital
(iv) Consider any element in the f-block
• The last electron in that element will be present in an f orbital
3. So we can write the general rule in 4 steps:
(i) Consider any block
(ii) Consider the last electron of each element in that block
(iii) All those 'last electrons' will be present in the same type of orbital (s, p, f or d)
(iv) The 'name of that orbital' will be same as the 'name of the block'
4. There are however, two exceptions to this rule:
A. Position of He
B. Position of H
Let us see them in detail:
A. Position of He
• The last electron of He enters the s orbital
• So we would expect He to be somewhere in the s-block
• But He is placed in Group 18 of the p-block
• The reason can be written in 4 steps:
(i) He is placed in Group 18
(ii) The elements of this group are called noble gases
• All elements in this group have completely filled valence orbitals
• He also has completely filled valence orbital
(iii) He exhibits chemical properties very similar to those of the noble gases
(iv) So the positioning of He in this group is justified
B. Position of H
• The one and only electron in H enters the s orbital
• So we would expect H to be somewhere in the s-block
• But H is not placed in any block
• It is placed separately at the top, away from the main body of the periodic table
• The reason can be written in 3 steps:
(i) Based on configuration, H can be placed in the Group 1
• This is because, in all the elements in that group, there is 1 electron in the outermost s orbital
(ii) The H can gain one more electron to attain the configuration of the nearest noble gas He
• All elements in the Group 17 also has the same condition
• Each of those elements in Group 17 can gain one more electron to attain the configuration of the nearest noble gas
(iii) So H has two possible positions
• The availability of two positions makes H a special case
• So it is placed separately
Group 1 and Group 2
Group 1:
1. Consider the electronic configuration of any element in the Group 1
2. Separate that electronic configuration into two parts:
(i) Configuration of the just previous noble gas core
(ii) Configuration outside the core
3. The configuration outside the core will be of the form ns1
• Where n is the period in which that element is situated
An example:
(i) Consider 37Rb
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p65s1
(ii) Separating it into two parts, we get: [1s22s22p63s23p63d104s24p6]5s1
• This is same as: [Kr]5s1
(iii) The portion outside the core is 5s1
(iv) We see that, the superscript of s is ‘1’
(v) Also we see that, the coefficient n is '5'
♦ 37Rb is indeed in the 5th period
Group 2:
1. Consider the electronic configuration of any element in the Group 2
2. Separate that electronic configuration into two parts:
(i) Configuration of the just previous noble gas core
(ii) Configuration outside the core
3. The configuration outside the core will be of the form ns2
• Where n is the period in which that element is situated
An example:
(i) Consider 56Ba
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p64d105s25p66s2
(ii) Separating it into two parts, we get: [1s22s22p63s23p63d104s24p64d105s25p6]6s2
• This is same as: [Xe]6s2
(iii) The portion outside the core is 6s2
(iv) We see that, the superscript of s is ‘2’
(v) Also we see that, the coefficient n is '6'
♦ 56Ba is indeed in the 6th period
4. So we can write the general configuration of the s-block elements:
[core]ns(1-2)
• Where n is the period in which that element is situated
♦ The superscript of s may be 1 or 2
♦ This superscript depends on the 'group number of the element'
♦ The relation is simple: Superscript = 'group number of the element'
5. How do we find the [core]?
Answer can be written in 3 steps:
(i) If we know the atomic number of the given element, we can easily spot the just previous noble gas
(ii) The [core] is the electronic configuration of that noble gas
(iii) Instead of writing the 'electronic configuration of that noble gas', it is enough to write it's symbol
The Groups 13 to 18
• In the s-block, there are only two groups
♦ So we wrote the steps for each group separately
• Here, in the p-block, there are 6 groups
♦ So we will write the steps in such a way that, they are applicable to all the 6 groups
1. Consider the electronic configuration of any element in the p-block
2. Separate that electronic configuration into two parts:
(i) Configuration of the just previous noble gas core
(ii) Configuration outside the core
3. For elements in the periods 1, 2 and 3:
• The configuration outside the core will be of the form ns2np(1-6)
• Where n is the period in which that element is situated
♦ The superscripts of s is a constant: 2
♦ The superscript of p may be any digit from 1 to 6
♦ This superscript depends on the 'group number of the element'
♦ The relation is: Superscript = 'group number of the element' - 12
♦ Note that, the p-block starts after the 12th period
4. For elements in the periods 4, 5, 6 and 7:
• The configuration outside the core will be of the form (n-1)d10ns2np(1-6)
• Where n is the period in which that element is situated
♦ The superscripts of d and s are constants: 10 and 2
♦ The superscript of p may be any digit from 1 to 6
♦ This superscript depends on the 'group number of the element'
♦ The relation is: Superscript = 'group number of the element' - 12
♦ Note that, the p-block starts after the 12th period
An example:
(i) Consider 14Si
• It’s electronic configuration is: 1s22s22p63s23p2
(ii) Separating it into two parts, we get: [1s22s22p6]3s23p2
• This is same as: [Ne]3s23p2
(iii) The portion outside the core is 3s23p2
(iv) We see that, the superscript of p is ‘2’
♦ Si belongs to the 14th group
♦ (14-12) is indeed 2
(v) Also we see that, the coefficient n is '3'
♦ 14Si is indeed in the 3rd period
Another example:
(i) Consider 34Se
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p4
(ii) Separating it into two parts, we get: [1s22s22p63s23p6]3d104s24p4
• This is same as: [Ar]3d104s24p4
(iii) The portion outside the core is 3d104s24p4
(iv) We see that, the superscript of p is ‘4’
♦ Se belongs to the 16th group
♦ (16-12) is indeed 4
(v) Also we see that, the coefficient n is '4'
♦ 34Se is indeed in the 4rd period
♦ Coefficient of d is (n-1) = (4-1) = 3
One more example:
(i) Consider 53I
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p64d105s25p5
(ii) Separating it into two parts, we get: [1s22s22p63s23p63d104s24p6]4d105s25p5
• This is same as: [Kr]4d105s25p5
(iii) The portion outside the core is 4d105s25p5
(iv) We see that, the superscript of p is ‘5’
♦ I belongs to the 17th group
♦ (17-12) is indeed 5
(v) Also we see that, the coefficient n is '5'
♦ 53I is indeed in the 5th period
♦ Coefficient of d is (n-1) = (5-1) = 4
5. So we can write the general configuration of the p-block elements:
(i) For elements in the periods 1, 2 and 3:
[core]ns2np(1-6)
(ii) For elements in the periods 4, 5, 6 and 7:
[core](n-1)d10ns2np(1-6)
• Where n is the period in which that element is situated
♦ The superscripts of d and s are constants: 10 and 2
♦ The superscript of p may be any digit from 1 to 6
♦ This superscript depends on the 'group number of the element'
♦ The relation is: Superscript = 'group number of the element' - 12
♦ Note that, the p-block starts after the 12th period
The Groups 3 to 12
• In this block, the last electron is added to the d orbitals
• We have seen earlier that some elements of the d-block deviates from the pattern
♦ Examples are chromium and copper
• However, we can write a general configuration:
[core](n-1)d(1-10)ns(0-2)
• Where n is the period in which that element is situated
♦ The superscripts of neither d nor s are constants
♦ The superscript of d may be any digit from 1 to 10
♦ The superscript of s may be 0, 1 or 2
♦ The upper row consists of lanthanides
♦ The lower row consists of actinides
• In this block, the last electron is added to the f orbitals
• However, some elements deviate from the pattern
• The general configuration is:
[core](n-2)f(1-14)(n-1)d(0-1)ns2
(i) The s-block and p-block elements strictly follow a pattern
(ii) We see patterns in the d-block and f-block also. But some of the elements in those blocks deviates from the pattern
■ The s-block and p-block elements are sometimes considered together as a single group
• This single group is called: The main group
• Another name for this single group is: Representative elements
• The main group elements are the most abundant elements on earth
2. We already know the names of each column:
♦ 1st column is called Group 1
♦ 2nd column is called Group 2
♦ 3rd column is called Group 13
♦ 4th column is called Group 14
♦ so on . . .
3. Consider any one from among the 8 groups
• All the elements in that group will be having similar properties
■ So the elements within a group can be considered to form a family
4. Thus we get 8 families
Each family is given a name. They are shown below:
Group 1: Alkali metals
Group 2: Alkaline earth metals
Group 13: Boron family
Group 14: Carbon family
Group 15: Nitrogen family
Group 16: Oxygen family
Group 17: Halogens
Group 18: Noble gases
5. Sometimes scientists and engineers refer to one or more of the above families in their documents
• So we must be able to distinguish between various families
• We will see more details in later sections
• All elements belonging to a group will have:
♦ Same 'valence electrons'
♦ Similar 'valence orbitals'
♦ Similar 'physical and chemical properties'
■ In this section, we will see the various blocks in the periodic table
1. The elements of the periodic table are classified into four blocks:
s-block, p-block, d-block and f-block
2. How did the blocks get those names?
Answer:
(i) Consider any element in the s-block
• The last electron in that element will be present in an s orbital
(ii) Consider any element in the p-block
• The last electron in that element will be present in an p orbital
(iii) Consider any element in the d-block
• The last electron in that element will be present in an d orbital
(iv) Consider any element in the f-block
• The last electron in that element will be present in an f orbital
3. So we can write the general rule in 4 steps:
(i) Consider any block
(ii) Consider the last electron of each element in that block
(iii) All those 'last electrons' will be present in the same type of orbital (s, p, f or d)
(iv) The 'name of that orbital' will be same as the 'name of the block'
4. There are however, two exceptions to this rule:
A. Position of He
B. Position of H
Let us see them in detail:
A. Position of He
• The last electron of He enters the s orbital
• So we would expect He to be somewhere in the s-block
• But He is placed in Group 18 of the p-block
• The reason can be written in 4 steps:
(i) He is placed in Group 18
(ii) The elements of this group are called noble gases
• All elements in this group have completely filled valence orbitals
• He also has completely filled valence orbital
(iii) He exhibits chemical properties very similar to those of the noble gases
(iv) So the positioning of He in this group is justified
B. Position of H
• The one and only electron in H enters the s orbital
• So we would expect H to be somewhere in the s-block
• But H is not placed in any block
• It is placed separately at the top, away from the main body of the periodic table
• The reason can be written in 3 steps:
(i) Based on configuration, H can be placed in the Group 1
• This is because, in all the elements in that group, there is 1 electron in the outermost s orbital
(ii) The H can gain one more electron to attain the configuration of the nearest noble gas He
• All elements in the Group 17 also has the same condition
• Each of those elements in Group 17 can gain one more electron to attain the configuration of the nearest noble gas
(iii) So H has two possible positions
• The availability of two positions makes H a special case
• So it is placed separately
Now we will discuss about the four blocks in some detail
The s-block
■ The s-block consists of two groups. They are:Group 1 and Group 2
Group 1:
1. Consider the electronic configuration of any element in the Group 1
2. Separate that electronic configuration into two parts:
(i) Configuration of the just previous noble gas core
(ii) Configuration outside the core
3. The configuration outside the core will be of the form ns1
• Where n is the period in which that element is situated
An example:
(i) Consider 37Rb
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p65s1
(ii) Separating it into two parts, we get: [1s22s22p63s23p63d104s24p6]5s1
• This is same as: [Kr]5s1
(iii) The portion outside the core is 5s1
(iv) We see that, the superscript of s is ‘1’
(v) Also we see that, the coefficient n is '5'
♦ 37Rb is indeed in the 5th period
Group 2:
1. Consider the electronic configuration of any element in the Group 2
2. Separate that electronic configuration into two parts:
(i) Configuration of the just previous noble gas core
(ii) Configuration outside the core
3. The configuration outside the core will be of the form ns2
• Where n is the period in which that element is situated
An example:
(i) Consider 56Ba
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p64d105s25p66s2
(ii) Separating it into two parts, we get: [1s22s22p63s23p63d104s24p64d105s25p6]6s2
• This is same as: [Xe]6s2
(iii) The portion outside the core is 6s2
(iv) We see that, the superscript of s is ‘2’
(v) Also we see that, the coefficient n is '6'
♦ 56Ba is indeed in the 6th period
4. So we can write the general configuration of the s-block elements:
[core]ns(1-2)
• Where n is the period in which that element is situated
♦ The superscript of s may be 1 or 2
♦ This superscript depends on the 'group number of the element'
♦ The relation is simple: Superscript = 'group number of the element'
5. How do we find the [core]?
Answer can be written in 3 steps:
(i) If we know the atomic number of the given element, we can easily spot the just previous noble gas
(ii) The [core] is the electronic configuration of that noble gas
(iii) Instead of writing the 'electronic configuration of that noble gas', it is enough to write it's symbol
The p-block
■ The p-block consists of 6 groups. They are:The Groups 13 to 18
• In the s-block, there are only two groups
♦ So we wrote the steps for each group separately
• Here, in the p-block, there are 6 groups
♦ So we will write the steps in such a way that, they are applicable to all the 6 groups
1. Consider the electronic configuration of any element in the p-block
2. Separate that electronic configuration into two parts:
(i) Configuration of the just previous noble gas core
(ii) Configuration outside the core
3. For elements in the periods 1, 2 and 3:
• The configuration outside the core will be of the form ns2np(1-6)
• Where n is the period in which that element is situated
♦ The superscripts of s is a constant: 2
♦ The superscript of p may be any digit from 1 to 6
♦ This superscript depends on the 'group number of the element'
♦ The relation is: Superscript = 'group number of the element' - 12
♦ Note that, the p-block starts after the 12th period
4. For elements in the periods 4, 5, 6 and 7:
• The configuration outside the core will be of the form (n-1)d10ns2np(1-6)
• Where n is the period in which that element is situated
♦ The superscripts of d and s are constants: 10 and 2
♦ The superscript of p may be any digit from 1 to 6
♦ This superscript depends on the 'group number of the element'
♦ The relation is: Superscript = 'group number of the element' - 12
♦ Note that, the p-block starts after the 12th period
An example:
(i) Consider 14Si
• It’s electronic configuration is: 1s22s22p63s23p2
(ii) Separating it into two parts, we get: [1s22s22p6]3s23p2
• This is same as: [Ne]3s23p2
(iii) The portion outside the core is 3s23p2
(iv) We see that, the superscript of p is ‘2’
♦ Si belongs to the 14th group
♦ (14-12) is indeed 2
(v) Also we see that, the coefficient n is '3'
♦ 14Si is indeed in the 3rd period
Another example:
(i) Consider 34Se
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p4
(ii) Separating it into two parts, we get: [1s22s22p63s23p6]3d104s24p4
• This is same as: [Ar]3d104s24p4
(iii) The portion outside the core is 3d104s24p4
(iv) We see that, the superscript of p is ‘4’
♦ Se belongs to the 16th group
♦ (16-12) is indeed 4
(v) Also we see that, the coefficient n is '4'
♦ 34Se is indeed in the 4rd period
♦ Coefficient of d is (n-1) = (4-1) = 3
One more example:
(i) Consider 53I
• It’s electronic configuration is: 1s22s22p63s23p63d104s24p64d105s25p5
(ii) Separating it into two parts, we get: [1s22s22p63s23p63d104s24p6]4d105s25p5
• This is same as: [Kr]4d105s25p5
(iii) The portion outside the core is 4d105s25p5
(iv) We see that, the superscript of p is ‘5’
♦ I belongs to the 17th group
♦ (17-12) is indeed 5
(v) Also we see that, the coefficient n is '5'
♦ 53I is indeed in the 5th period
♦ Coefficient of d is (n-1) = (5-1) = 4
5. So we can write the general configuration of the p-block elements:
(i) For elements in the periods 1, 2 and 3:
[core]ns2np(1-6)
(ii) For elements in the periods 4, 5, 6 and 7:
[core](n-1)d10ns2np(1-6)
• Where n is the period in which that element is situated
♦ The superscripts of d and s are constants: 10 and 2
♦ The superscript of p may be any digit from 1 to 6
♦ This superscript depends on the 'group number of the element'
♦ The relation is: Superscript = 'group number of the element' - 12
♦ Note that, the p-block starts after the 12th period
The d-block
■ The d-block consists of 10 groups. They are:The Groups 3 to 12
• In this block, the last electron is added to the d orbitals
• We have seen earlier that some elements of the d-block deviates from the pattern
♦ Examples are chromium and copper
• However, we can write a general configuration:
[core](n-1)d(1-10)ns(0-2)
• Where n is the period in which that element is situated
♦ The superscripts of neither d nor s are constants
♦ The superscript of d may be any digit from 1 to 10
♦ The superscript of s may be 0, 1 or 2
The f-block
• The f-block consists of two rows placed below the periodic table♦ The upper row consists of lanthanides
♦ The lower row consists of actinides
• In this block, the last electron is added to the f orbitals
• However, some elements deviate from the pattern
• The general configuration is:
[core](n-2)f(1-14)(n-1)d(0-1)ns2
• Where n is the period in which that element is situated
♦ The superscripts of s is a constant: 2
♦ The superscripts of neither d nor f are constants
♦ The superscript of d may be 0 or 1
♦ The superscript of f may be any digit from 1 to 14
• From the above discussion, we notice two points:♦ The superscript of d may be 0 or 1
♦ The superscript of f may be any digit from 1 to 14
(i) The s-block and p-block elements strictly follow a pattern
(ii) We see patterns in the d-block and f-block also. But some of the elements in those blocks deviates from the pattern
■ The s-block and p-block elements are sometimes considered together as a single group
• This single group is called: The main group
• Another name for this single group is: Representative elements
• The main group elements are the most abundant elements on earth
Families in the periodic table
1. We see that, in the main group, there are 8 vertical columns2. We already know the names of each column:
♦ 1st column is called Group 1
♦ 2nd column is called Group 2
♦ 3rd column is called Group 13
♦ 4th column is called Group 14
♦ so on . . .
3. Consider any one from among the 8 groups
• All the elements in that group will be having similar properties
■ So the elements within a group can be considered to form a family
4. Thus we get 8 families
Each family is given a name. They are shown below:
Group 1: Alkali metals
Group 2: Alkaline earth metals
Group 13: Boron family
Group 14: Carbon family
Group 15: Nitrogen family
Group 16: Oxygen family
Group 17: Halogens
Group 18: Noble gases
5. Sometimes scientists and engineers refer to one or more of the above families in their documents
• So we must be able to distinguish between various families
• We will see more details in later sections
In the next section, we will see the classification into metals and non-metals
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