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INORGANIC CHEMISTRY


Is the chemistry of all the elements and their compounds with the exception of most carbon compounds out of which only the oxides, cyanides and carbonates are considered as inorganic compound. Inorganic compound can also be defined as the study of the elements in the periodic table.

PERIODIC TABLE

Periodic table is the table of all the known elements arranged in order of increasing atomic numbers. The arrangement reflects the electronics configuration of the elements.

THE PERIODIC TABLE CLASSIFICATION OF THE ELEMENTS (MENDELEEV’S AND LOTHAR MEYER 1869)

The first comprehensive classification of elements was made independently by Mendeleev’s in Russia and Lothar Meyer in German in 1869.They tabulated all the known elements on the basis of relative atomic mass. The arrangement of elements in the early periodic table was according to the ordinary periodic law which states that ‘The properties of elements are periodic function of their relative atomic masses’.
When elements were arranged in order of increasing atomic masses, elements with similar properties recurred at regular intervals .The recurrence or repetition of elements with similar properties of regular intervals in the periodic table is known as PERIODICITY.
Mendeleev’s and Lothar Meyer placed elements in horizontal rows (periods) which caused elements with similar properties to appear in the same vertical column (group). Some element were not yet discovered and hence absent that periodic table e.g. Noble gases, gallium ,germanium etc.
On the basis of relative atomic mass three anomalies appeared in the early periodic table (Ordinary periodic table). The position of Potassium (39.1), Argon (39.9), Cobalt (58.94), Nickel (58.69), Tellurium (127.6) and Iodine (126.9) had to be reversed to bring them into correct placing on chemical grounds. The strict order of relative atomic mass would have separated the mentioned elements from closely related element. For example Potassium could have been separated from other alkali metals. These anomalies showed clearly that the relative atomic mass was not really the true basis of arranging or classifying elements in the periodic table.
The three anomalies stated above were due to ISOTOPE. For example both Argon and Potassium exhibit isotropy .The principal Isotopes of these elements are shown in the table below.
In the case of Argon, the heavier isotope is predominate(has higher abundance) giving an average atomic mass of 39.9,In Potassium the lighter isotope predominates giving an average atomic mass of 39.1, The explanation is similar in the case of cobalt(no isotopes) and nickel(five isotope) and tellurium(8 isotopes) and iodine(isotope)
Moseley discovered that atomic number was the proper criterion for arranging elements in the periodic table. The atomic number of an element determines the number of electronics in the atom and hence the arrangement and properties of the elements in the periodic table.
When atomic numbers are used instead of atomic masses, the anomalies observed between potassium ,Argon ,Cobalt ,Nickel Tellurium and Iodine disappears .The classification of the known elements in the periodic table is now based on the Modern Periodic law which states that “ The properties of elements are periodic function of their atomic numbers”
NB: One can’t use R.A.M or Atomic mass for arranging elements but atomic number is the best

STRUCTURE OF PERIODIC TABLE

The periodic table is very important in the study of inorganic chemistry. The relationship between the periodic table, atomic number and properties of elements enable us to obtain an overview of the many facts and features in Inorganic chemistry
The periodic table consist of boxes which are filled by elements .Each box contains the symbol, mass number, and atomic number of elements.
However, other data like electronegativity, boiling point, melting point, oxidation states values may be included or added. There are various lay out of the period table. The periodic table may be in the short or long form .Under this level the long form will be considered .The long form consists of all the elements of a periodic except the Lanthanide and Actinides
The elements with similar properties occur in vertical column called groups. The horizontal rows of elements in the periodic table are calling periods. The long form of the periodic table is into four major blocks according to the sub shell in which the respective elements fill their electronics. The four major blocks are S-blocks, P-blocks, d-bloc
ks, and f- blocks.

1. S-BLOCK ELEMENTS
The S-blocks consist of elements which fills their outermost electrons in the S-sub shell. These elements use their S-sub shell electrons for bonding. The S-block is constituted by the element of Group IA and Group IIA e.g. Li, Na, K, Mg etc

2. P-BLOCK ELEMENTS

The P-blocks elements consist of elements which fills their outermost electrons in the P-sub shell. This block consist of elements of group IIIA up to VIIA example Carbon, Sulphur ,Phosphorus ,Nitrogen ,Oxygen, Chlorine, Argon ,Neon, Helium is not a P-block elements.
The S-and P-blocks elements together form main group elements .These elements use only electrons of their outermost shell for bonding .Hence there are seven main groups which constitute main group elements (example IA, IIA, III,IVA, VA, VIA and VIIA). The noble gas contains full outermost electrons S and P-sub shells. Since this configuration is very stable, the noble gases are uncreative.
However they form some compounds with strongly electronegative elements like Oxygen and Fluorine .Example of noble gases include Helium, Neon, Argon, Krypton etc
3. d-BLOCK ELEMENTS
The d-blocks consist of elements with partially or full-filled d-sub shell. They fill their electrons in the d-sub shell of the penultimate shell. They use electrons from S and d-sub shells for bonding. Example Scandium, Manganese, Iron, Radium, Nickel, Cobalt, Copper, Zinc etc

4. f-BLOCK ELEMENT
The f-block consists of elements which are called Lanthanides and Actinides. They are also known inner transition elements. These elements have two partially filled sub-shells namely (n-1)d and (n-2)f .They all belong to III B because they are so similar that it is very difficult to separate one from another example e.g. La, U, Np ,Lw, Th etc
NOTE;
I. The atoms of all elements of the same period have the same number of shells which are partially or fully occupied by electrons.
II. The number of the main groups is equal to the number of electrons in the outermost shell.
III. The number of period is equal to the principal quantum number (n) of the outermost shell and to the total number of electrons shell of the elements in a given period.

PERIODIC TRENDS IN PHYSICAL PROPERTIES

1. DOWN THE GROUP

I. I. The atomic size(Atomic Radius)
The atomic radius of an uncombined atom cannot be defined strictly because of the uncertain boundary of electron clouds .The distance between the nuclei of chemically or covalently combined atoms can be measured accurately by x-ray diffraction method
Therefore, the atomic radius is defined as half the distance between the nuclei of two similar/ identical atoms joined by a single covalent or metallic bond. There is significant regular increase in atomic radii among elements down t
he group .This trend is due to increase of number of electrons and number and number of shells down the group.
The newly added electrons or shell must be at greater distance from the nucleus than that of the proceeding element (i.e a noble gas). Also the added electron is shielded by the inner electrons. Therefore the added shells and electrons reduces the attraction force between the nucleus and the outer electrons leading to increase in atomic size down the group .The following is the trend down group IA.


II. Ionic radii

The ionic radius of the atom of an element is measured in the same way as the atomic radius. The ionic radii like atomic radii increases down the group. The reasons for this are exactly the same as those quoted for atomic radii. The radius of a cation is shorter than the radius of the parents atom (neutral atom) because electron or electrons have been removed and hence the force of attraction from the nucleus has increased e.g. Na=1.57, 0.97

I

53

0.133

0.216

I

III. Ionization energy

IV. Electron affinity (E.A)

NB: From the table above Chlorine has higher electron affinity than Fluorine. This is probability due to the relative small atomic size of Fluorine compared to that of Chlorine. The higher electron cloud in small Fluorine atom exerts a great repulsive force to the incoming electron giving rise to a smaller value of electron affinity. Chlorine with larger atomic size has smaller repulsive force and as result an electron can easily to be added to it and hence high electron affinity. All the electron affinity valves quoted for univalent ions is negative .To add an electrons to a univalent anion may require a large amount of energy in order to overcome electrostatic repulsion between the second electron and the charge on the anion. For example the second electron affinity of oxygen is positive.

PERIODIC TRENDS IN CHEMICAL PROPERTIES ACROSS PERIOD THREE (Na to Ar)

a) HYDRIDES

REACTION OF HYDRIDES WITH WATER

b) CHLORIDES

REACTION OF CHLORIDES WITH WATER

c) THE HYDROXIDES

d) OXIDES

DIAGONAL RELATIONSHIP BETWEEN THE ELEMENTS

LITHIUM AND MAGNESIUM.

BERYLIUM AND ALUMINIUM

QUESTION

ANOMALOUS BEHAVIOUR OF THE FIRST ELEMENT IN A GROUP OF THE PERIODIC TABLE

ANOMALOUS BEHAVIOUR OF LITHIUM

ANOMALOUS BEHAVIOUR OF BERYLIUM

ANOMALOUS BEHAVIOUR OF FLUORINE

SELECTED COMPOUNDS OF METALS.
(i.e COMPOUNDS OF Na, Mg, Ca, Al, Fe, Zn, Cu AND Pb)

METAL OXIDES

GENERAL METHODS IN PREPARATION OF METAL OXIDES.
There are two methods of preparing metal oxides

1. BASIC OXIDES

3. AMPHOTERIC OXIDE

4. PEROXIDES

5. SUPEROXIDES

6. MIXED OXIDES

FERROUS –FERRIO OXIDE (Fe3O4) (FeO.Fe2O3)

HYDROXIDES OF THE METALS



USES

1. Lime water is used to test for carbon dioxide.

2. A suspension of Magnesium hydroxide in water (milk of magnesium)is used as an ant-acid.

3. Ca(OH)2 is used in making builders mortar (mixture of slaked lime, sand and water).

4. A mixture of Ca(OH)2 is used in making bleaching powder.

5. Ca(OH)2 is used for neutralizing acids in the soil.

6. A mixture Ca(OH)2 and water (white wash) is used for coating walls and ceiling.

7. Ca(OH)2 is used in water softening.




8. Ca(OH2) is used in sugar refining filtered.

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2 Comments

  • Fares, December 9, 2023 @ 6:49 am Reply

    Nice

  • I D, December 2, 2023 @ 8:48 pm Reply

    Quite useful!

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