Chapter 8.8 - Inorganic compounds of Carbon

In the previous section, we saw the different allotropes of carbon. In this section we will learn about the isotopes of carbon.

■ Isotopes are atoms of the same element, having same atomic number Z, but different mass number A
• They will have the same Z because, the number of protons in all those atoms will be the same
• They have different mass numbers because, the number of neutrons will be different.
• We saw the details earlier here.

■ Carbon-12, carbon-13 and carbon-14 are the different isotopes of carbon.
• 99% of the carbon that occurs in nature is in the form of carbon-12
    ♦ The mass of carbon-12 atom is taken as the reference for expressing the atomic masses of other elements. We saw details here.
• Carbon-14 is a radioactive isotope. The presence of this isotope in a material can be used to determine the age of that material. This method of determining age is called carbon dating.   

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Compounds of Carbon
• Earlier in this chapter, we saw hydrocarbons. They are compounds of carbon which are formed when carbon combines with hydrogen
• Now we will see those compounds which are formed when carbon combines with some other elements
Carbon dioxide
• Carbon dioxide is a gas present in the atmosphere. It is produced mainly by the combustion of fuels.
■ How is carbon dioxide produced when combustion of fuels takes place?
• The fuels contain carbon or 'compounds of carbon'
• When the fuels burn, this carbon or ‘compounds of carbon’ reacts with oxygen. This reaction produces carbon dioxide. Let us see the equations:
• Reaction of carbon with oxygen: 
C + O₂ → CO₂
• Reaction of a 'compound of carbon' with oxygen:
CH₄ + 2O₂ → CO₂ + 2H₂O

Properties of Carbon dioxide

• It is colourless • It does not support combustion • It is denser than air • It is odourless

Carbon dioxide cycle

The carbon dioxide in the earths atmosphere is continuously recycled. Let us see how this recycling occurs:
• During photosynthesis, plants take in carbon dioxide from the atmosphere. 
• They use it to prepare food. Thus the carbon becomes part of the plant body. 
• These plants are eaten by animals. Then the carbon becomes part of the animal body. 
• When the animals respire, they take in oxygen. The carbon in their body is given out as carbon dioxide. 
• Thus the carbon dioxide enters back into the atmosphere.
Another way:

• When the plants and animals decay, they are converted into coal and petroleum. These are fossil fuels.
• When these fossil fuels are burnt, carbon dioxide is produced. In this way also, the carbon dioxide enters back into the atmosphere.

Uses of carbon dioxide

• Used in fire extinguishers
• Used to make soda water and soft drinks
• Used in the manufacture of washing soda and baking soda
• Used in the manufacture of chemical fertilisers like urea
• Used in carbogen (95% oxygen and 5 % carbon dioxide) used for artificial respiration

• The solid form of carbon dioxide is called dry ice. It is used as a refrigerant and also to create stage effects resembling clouds

Green house effect and Global warming

• In the sunlight that the earth receives, infra red rays and ultra violet rays are also present. 
• The infra red rays are thermal radiations. They are referred to as heat waves also. Because they tend to increase the temperature of substances upon which they fall.
• The carbon dioxide in the atmosphere will trap a portion of these infra red radiations which are radiated back from the earth. 
• This will help to maintain warmth on the surface of earth. And it is called the green house effect.
• But if the quantity of carbon dioxide increases too much in the atmosphere, greater portion of the infra red radiations will get trapped. 
• This will increase the temperature of the earth beyond normal. This is called global warming.

■ Global warming causes many serious problems. Some of them are:
• Rise in sea levels due to the melting of polar ice caps and glaciers
• Increase in wild fires
• Increase in heat waves during summer
• Overall change in climate
• Disruption to agriculture due to shortage of rainfall
• Greater number of people affected by diseases

• Disruption to animal and plant life

Carbon monoxide

• We have seen that, when carbon reacts with oxygen, carbon dioxide is produced
• But if 
    ♦ the quantity of carbon is more when compared to the quantity of oxygen OR
    ♦ the quantity of oxygen is less when compared to the quantity of carbon,

incomplete combustion of carbon will take place. 
• This incomplete combustion will lead to the formation of carbon monoxide. 

■ To avoid incomplete combustion, we must always provide proper ventilation for engines that uses combustion of fuels. 
■ Also properly maintain all engines and equipments in good condition. Take all safety precautions and strictly follow instruction manuals.

Uses of carbon monoxide
Though carbon monoxide is poisonous, it has several uses. Some of them are:
• Used as a gaseous fuel • Used to produce industrial gases like water gas and producer gas • Used as a reducing agent in metallurgy

Carbonates and bicarbonates
• These are also compounds of carbon
• Marble, which is calcium carbonate (CaCO₃ ), and Baking soda which is Sodium bicarbonate (NaHCO₃) are examples

• They react with acids. We saw the details here.
• So reactions with acids can be used to identify carbonates and bicarbonates

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In the next section, we will learn about Subshell electronic configuration. 

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Chapter 8.7 - Allotropes of Carbon

In the previous section, we saw the three dimensional arrangement of atoms. In this section we will learn about Allotropes.

■ Let us see some basic details about diamond:
• It contain only one element, and that is carbon. 
• The carbon atoms are held together by covalent bonds. All the covalent bonds are single bonds. 
• Each carbon atom is bonded to four other carbon atoms. They form a tetrahedron network. The tetrahedron arrangement in diamond can be seen here.
■ So the diamond is made up of carbon atoms arranged in a 3D space. 
• All those atoms are interconnected. The interconnection is by strong covalent bonds. This makes diamonds very hard. 
• They are used in cutting tools for glass, brick, concrete etc.,
• Diamonds do not conduct electricity. This is because of the absence of any free electrons.
■ Some more properties of diamonds are listed below:
• Diamonds have high refractive index. 
• Pure diamond is transparent. 
• When diamonds are cut by experts, they sparkle and reflect light in an attractive way. 
• They also give off different colours because of the refraction of white light. So they are used in jewellery.
• Diamonds are good conductors of heat. 

Now let us see some basic details about graphite:
• We have seen that, in diamond, the carbon atoms are situated at the corners of a tetrahedron. A tetrahedron is a 'three dimensional' figure. 
• But in the case of graphite, the carbon atoms are situated at the corners of a hexagon. 
• A hexagon is a 'two dimensional' figure. These 'two dimensional hexagons' are connected to each other. So they form 'two dimensional layers'. This arrangement can be seen here. 
• These layers are stacked one above the other. When so many such layers are stacked, we get a solid appearance.
    ♦ For example, when two or three sheets of paper are stacked, it will still be two dimensional. But when a very large number of sheets of paper are stacked, we get a three dimensional or solid appearance. 
• But there is no connection between those individual layers. The layers are kept together only by weak van der waals physical forces. So the layers can slide over one another

Now let us see some properties of graphite:
• Since the layers slide over one another, they are slippery and hence used as solid state lubricants. This is shown here.
• Graphite is a good conductor of electricity. This is because free electrons are present in it. Free electrons are available because, those electrons are not required for bonding.  
• So it is used to make electrodes in dry cells
• It is used to make pencils. This is because of it's smoothness and grey colour.
    ♦ In early days, when graphite was newly discovered, people thought it was black lead. So pencils made of them got the name lead pencils
• Graphite is lustrous and non volatile

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■ So we have seen two substances. Diamond and graphite. They have different properties. 

• But one thing is common. That is., they contain carbon atoms only. No other atoms are present. 

• So we can say that carbon exists in two different forms. 
    ♦ In diamond carbon is in one form
    ♦ In graphite carbon is in another form
• There are a few other forms also for carbon
■ Allotropy is the phenomenon by which the same element exists in different physical forms.
■ Diamond and graphite are allotropes of carbon
• We have seen allotropes of oxygen here.

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Now let us see some other allotropes of carbon

• We have seen diamond in which carbon atoms are placed at the corners of three dimensional tetrahedron

• We have seen graphite in which carbon atoms are placed at the corners of two dimensional hexagon

■ Now we will see fullerene.

• In fullerene, carbon atoms are placed at the corners of two dimensional hexagons and pentagons. 

• These hexagons and pentagons are connected together. 

    ♦ Just like hexagons are connected together to form a layer in graphite

• But in fullerene, the interconnected hexagons and pentagons do not remain as a layer.

• Instead, they form a spherical shape as in a foot ball. The sphere is hollow inside. So it is like a spherical cage. A figure can be seen here. 

    ♦ One spherical cage is one molecule of fullerene. 

    ♦ They are also known as Bucky balls

• If, instead of forming a sphere, the sheet rolls into a cylinder, we get a cylidrical cage. 

    ♦ Then they are known as Bucky tubes 

■ Another allotrope of carbon is graphene. Let us see some of it's basic details:

• We have see the details of graphite. Take out one layer of graphite.

    ♦ This one layer of graphite is graphene. 

• So graphene is a layer having a thickness equal to the thickness of one carbon atom. Some images can be seen here.

• Such a one atom thick layer has special uses in nano technology. We will learn more details about graphene in higher classes

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In the next section, we will learn about Isotopes of Carbon. 

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Chapter 9.2 - Electronic configuration of elements from Vanadium to Zinc

In the previous section, we saw the electronic configuration upto the twenty second element. That is., up to Titanium. In this section we will see elements from twenty three to thirty.

23. Twenty third element Vanadium (V):

(i) V has an atomic number 23. It has 23 electrons.
(ii) We have seen how 22 electrons are distributed when we saw Ti. The 3d subshell is being filled up.

(iii) Any d subshell can accommodate 10 electrons. Out of these 10, only 2 is used up in Ti  

(iv) So the Twenty third electron in V can be easily accommodated in 3d. This gives us 3d³.

■ So the S.E.C of V is 1s²2s²2p⁶3s²3p⁶4s²3d³

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Let us write the  configurations of the 23 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³

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24. Twenty fourth element Chromium (Cr):

(i) Cr has an atomic number 24. It has 24 electrons.
(ii) We have seen how 23 electrons are distributed when we saw V. The 3d subshell is being filled up.

(iii) Any d subshell can accommodate 10 electrons. Out of these 10, only 3 is used up in V 

(iv) So the Twenty fourth electron in Cr can be easily accommodated in 3d. This gives us 3d⁴.

■ So we would expect the final configuration of Cr to be 1s²2s²2p⁶3s²3p⁶4s²3d⁴
■ But unfortunately, this is not the case. Let us analyse:
(a) The configuration of the previous element V is 1s²2s²2p⁶3s²3p⁶4s²3d³.
(b) When the next electron is added in chromium, 3d³ becomes 3d⁴.
(c) Now, any d subshell can accommodate 10 electrons. Half of 10 is 5. 
    ♦ A completely full d subshell (that is., d¹⁰) AND
    ♦ A half full d subshell (that is., d⁵)
• has greater stability than partially filled d subshell
(d) So the 3d⁴ tries to become 3d⁵.
(e) For that, an electron in the 4s jumps to 3d
(f) Thus, 4s² becomes 4s¹ and 3d⁴ becomes 3d⁵.
■ So the S.E.C of Cr is 1s²2s²2p⁶3s²3p⁶4s¹3d⁵ 

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Let us write the  configurations of the 24 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵.

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25. Twenty fifth element Manganese (Mn):

(i) Mn has an atomic number 25. It has 25 electrons.
(ii) We have seen how 24 electrons are distributed when we saw Cr. One electron jumped away from 4s. The 4s is now half filled. It can accommodate one more electron
(iii) So the Twenty fifth electron in Mn will go to 4s, giving us 4s² from 4s¹.

■ So the S.E.C of Mn is 1s²2s²2p⁶3s²3p⁶4s²3d⁵ 

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Let us write the  configurations of the 25 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵.
25. Mn    - 1s²2s²2p⁶3s²3p⁶4s²3d⁵  OR [Ar]4s²3d⁵.

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26. Twenty sixth element Iron (Fe):

(i) Fe has an atomic number 26. It has 26 electrons.
(ii) We have seen how 25 electrons are distributed when we saw Mn. 4s was completed
(iii) The 3d now has 5 electrons. It can accommodate a total of 10. 
(iv) So the twenty sixth electron in Fe goes to the 3d, giving us 3d⁶.
■ So the S.E.C of Fe is 1s²2s²2p⁶3s²3p⁶4s²3d⁶ 

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Let us write the  configurations of the 26 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵
25. Mn   - 1s²2s²2p⁶3s²3p⁶4s²3d⁵  OR [Ar]4s²3d⁵
26. Fe    - 1s²2s²2p⁶3s²3p⁶4s²3d⁶  OR [Ar]4s²3d⁶.

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27. Twenty seventh element Cobalt (Co):

(i) Co has an atomic number 27. It has 27 electrons.
(ii) We have seen how 26 electrons are distributed when we saw Fe. 3d is now being filled up.
(iii) The 3d now has 6 electrons. It can accommodate a total of 10. 
(iv) So the twenty seventh electron in Co goes to the 3d, giving us 3d⁷.
■ So the S.E.C of Co is 1s²2s²2p⁶3s²3p⁶4s²3d⁷

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Let us write the  configurations of the 27 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵
25. Mn    - 1s²2s²2p⁶3s²3p⁶4s²3d⁵  OR [Ar]4s²3d⁵
26. Fe    - 1s²2s²2p⁶3s²3p⁶4s²3d⁶  OR [Ar]4s²3d⁶
27. Co    - 1s²2s²2p⁶3s²3p⁶4s²3d⁶  OR [Ar]4s²3d⁷.

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28. Twenty eighth element Nickel (Ni):

(i) Ni has an atomic number 28. It has 28 electrons.
(ii) We have seen how 27 electrons are distributed when we saw Co. 3d is now being filled up.
(iii) The 3d now has 7 electrons. It can accommodate a total of 10. 
(iv) So the twenty eighth electron in Ni goes to the 3d, giving us 3d⁸.
■ So the S.E.C of Ni is 1s²2s²2p⁶3s²3p⁶4s²3d⁸

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Let us write the  configurations of the 28 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵
25. Mn    - 1s²2s²2p⁶3s²3p⁶4s²3d⁵  OR [Ar]4s²3d⁵
26. Fe    - 1s²2s²2p⁶3s²3p⁶4s²3d⁶  OR [Ar]4s²3d⁶
27. Co    - 1s²2s²2p⁶3s²3p⁶4s²3d⁷  OR [Ar]4s²3d⁷
28. Ni    - 1s²2s²2p⁶3s²3p⁶4s²3d⁸  OR [Ar]4s²3d⁸

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29. Twenty ninth element Copper (Cu):

(i) Cu has an atomic number 29. It has 29 electrons.
(ii) We have seen how 28 electrons are distributed when we saw Ni. The 3d subshell is being filled up.

(iii) Any d subshell can accommodate 10 electrons. Out of these 10, only 8 is used up in Ni 

(iv) So the Twenty ninth electron in Cu can be easily accommodated in 3d. This gives us 3d⁹.

■ So we would expect the final configuration of Cu to be 1s²2s²2p⁶3s²3p⁶4s²3d⁹
■ But unfortunately, this is not the case. Let us analyse:
(a) The configuration of the previous element Ni is 1s²2s²2p⁶3s²3p⁶4s²3d⁸.
(b) When the next electron is added in chromium, 3d⁸ becomes 3d⁹.
(c) Now, any d subshell can accommodate 10 electrons. As we have seen in the case of chromium above,
    ♦ A completely full d subshell (that is., d¹⁰)
• has greater stability than partially filled d subshell
(d) So the 3d⁹ tries to become 3d¹⁰.
(e) For that, an electron in the 4s jumps to 3d
(f) Thus, 4s² becomes 4s¹ and 3d⁹ becomes 3d¹⁰
■ So the S.E.C of Cu is 1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰ 

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Let us write the  configurations of the 29 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵
25. Mn    - 1s²2s²2p⁶3s²3p⁶4s²3d⁵  OR [Ar]4s²3d⁵
26. Fe    - 1s²2s²2p⁶3s²3p⁶4s²3d⁶  OR [Ar]4s²3d⁶
27. Co    - 1s²2s²2p⁶3s²3p⁶4s²3d⁷  OR [Ar]4s²3d⁷
28. Ni    - 1s²2s²2p⁶3s²3p⁶4s²3d⁸  OR [Ar]4s²3d⁸
29. Cu    - 1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰  OR [Ar]4s¹3d¹⁰

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30. Thirtieth element Zinc (Zn):
(i) Zn has an atomic number 30. It has 30 electrons.

(ii) We have seen how 29 electrons are distributed when we saw Cu. One electron jumped away from 4s. The 4s is now half filled. It can accommodate one more electron
(iii) So the Thirtieth electron in Zn will go to 4s, giving us 4s² from 4s¹.

■ So the S.E.C of Zn is 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰ 

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Let us write the  configurations of the 30 elements together:

1. H      - 1s¹

2. He    - 1s² 

3. Li      - 1s²2s¹

4. Be     - 1s²2s²

5. B      - 1s²2s²2p¹

6. C      - 1s²2s²2p²

7. N      - 1s²2s²2p³
8. O      - 1s²2s²2p⁴
9. F       - 1s²2s²2p⁵
10. Ne  - 1s²2s²2p⁶
11. Na  - 1s²2s²2p⁶3s¹ OR [Ne]3s¹
12. Mg  - 1s²2s²2p⁶3s²  OR [Ne]3s²
13. Al    - 1s²2s²2p⁶3s²3p¹  OR [Ne]3s²3p¹
14. Si    - 1s²2s²2p⁶3s²3p² OR [Ne]3s²3p²
15. P    - 1s²2s²2p⁶3s²3p³ OR [Ne]3s²3p³
16. S    - 1s²2s²2p⁶3s²3p⁴  OR [Ne]3s²3p⁴
17. Cl    - 1s²2s²2p⁶3s²3p⁵. OR [Ne]3s²3p⁵
18. Ar   - 1s²2s²2p⁶3s²3p⁶
19. K    - 1s²2s²2p⁶3s²3p⁶4s¹ OR [Ar]4s¹
20. Ca   - 1s²2s²2p⁶3s²3p⁶4s²  OR [Ar]4s²
21. Sc   - 1s²2s²2p⁶3s²3p⁶4s²3d¹  OR [Ar]4s²3d¹
22. Ti    - 1s²2s²2p⁶3s²3p⁶4s²3d²  OR [Ar]4s²3d²
23. V    - 1s²2s²2p⁶3s²3p⁶4s²3d³  OR [Ar]4s²3d³
24. Cr    - 1s²2s²2p⁶3s²3p⁶4s¹3d⁵  OR [Ar]4s¹3d⁵.
25. Mn    - 1s²2s²2p⁶3s²3p⁶4s²3d⁵  OR [Ar]4s²3d⁵
26. Fe    - 1s²2s²2p⁶3s²3p⁶4s²3d⁶  OR [Ar]4s²3d⁶
27. Co    - 1s²2s²2p⁶3s²3p⁶4s²3d⁷  OR [Ar]4s²3d⁷.
28. Ni    - 1s²2s²2p⁶3s²3p⁶4s²3d⁸  OR [Ar]4s²3d⁸.
29. Cu    - 1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰  OR [Ar]4s¹3d¹⁰.
30. Zn    - 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰  OR [Ar]4s²3d¹⁰.

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We have written the electronic configuration for the first thirty elements. In the next section, we will see some of the applications of this type of configuration. 

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