General structure of alpha amino acids

The compounds containing amino group and carboxylic acid group are called amino acids.
Amino acids are monomers of proteins. 20 amino acids have been discovered yet.


R — C — COOH (Carboxylic acid group)
NH 2 (amino group)

IA and IIA elements

The elements in which the last electron enters in the s-orbital are called s-block elements.
These include the following:

  •  I-A group elements (except Hydrogen), Alkali metals
  • II-A group elements, Alkaline earth metals and Helium

Alkali metals:

  • The elements of group I-A except Hydrogen are called as Alkali metals.
  • The word alkali is an Arabic word which means The Ashes.
  • The Arabs used this word for these metals because they found that ashes of plants
    were composed chiefly of sodium and potassium.

Alkali metals include elements of Lithium (3Li), Sodium (iiNa), Potassium (1 .9K), Rubidium (37Rb), Cesium (55Cs), and Francium (81 Fr). These are very reactive metals and produce strong alkaline solutions with water.
Alkaline earth metals: II-A group elements are called Alkaline earth metals. They are called alkaline earth metals because they are metallic in nature producing alkalies in the water and are widely distributed in the earth crust.
These include Beryllium (4Be), Magnesium (12MA Calcium (2OCa), Strontium (385r), Barium (56Ba), and Radium (88Ra).
The Alkali metals and alkaline earth metals include the most reactive electropositive elements and the study of their electronic configuration will help us in understanding their properties.

Electronic Configuration of s-Block Elements:

Alkali metals:
Alkali metals have only one electron in the 's' orbital of their valence shell (ns 1 ). t
All alkali metals lose one electron of the valence shell to form monopositive ion (M ), because their ionization energy values are very Mi . Mi + le

They form ionic compounds and show +1 oxidation state. The electronic configuration and some physical constants of alkali metals are given in the table below.

Electronic configurations 1 s 2 2s 1 [N e]3 s 1 [Kr]4s 1 [Kr]5 s
Ionization energy (kJ/m ol) 520 496 419 403
Electron affinity (kJ/m ol) -60 -53 -48 -47
Electronagetivity 1.0 0.9 0.8 0.8

Melting points ( ° C) 187.0 97.5 63.6 39.0
Boiling points CC) 1325 889 774 688
Density gm /cm at
(20°C) 0.53 0.97 0.86 1.53
H eat of hydration (kJ/m ol) 505 475 384 345

Alkaline earth metals:

Alkaline earth metals have two electrons in the orbital of their valence shell (ns 2 ). All alkaline earth metals lose their two electrons to form dipositive ions (M4 ), because their ionization energies are M M 2 + 2e –

  •  They form ionic compounds and show +2 oxidation states.
  • The electronic configuration and some physical constants of alkaline earth metals
    are given in the table.

The names of neutral ligands are usually unchanged, e.g. for NH3, ammine and
for H2O, aqua. Formation and nomenclature, colors of complex compounds

Formation and Nomenclature (Rules for ligands naming only:)

The nomenclature of complex compounds is based upon the recommendations by inorganic nomenclature committee of IUPAC. The rules for naming the complex compounds are as follows.
(1) Cations are named before anions.
(2) In naming the coordination sphere, ligands are named in alphabetical order regardless
of the nature and number of each, followed by the name of the central metal ion.

(3) The prefixes di, tri, tetra, penta, hexa, etc, are used to specify the number of coordinated
(4) The name of anionic ligands end in suffix 0, e.g. hydroxo, (OH) carbonato (CO3 2- ).
Rules for metal naming only:
(6) The suffix at comes at the end of the name of metal if the complex represents an
anion, otherwise it remains unchanged.
(7) The oxidation number of the metal ion is represented by a Roman numeral in parenthesis followed by the name of the metal.
Examples: K4[Fe(CN)6] Potassium hexacyano ferrate (II)[PtCI(NO2)(NH3)4]SO4 Tetraammine chloronitro-platinum (IV) sulphate [Co (NO2)3(NH3)31 Triammine trinitrocobalt (III)

The rule for writing the formula of the complex:

(i) The complex may absorb the whole of white light. In this case, complex appears black.
(ii) The complex may reflect or transmit the whole light. In this case, it appears white.

In writing the formula of a complex ion, the usual practice is to place the symbol of the central metal atom first, followed by the formulae of the ionic ligands in alphabetical order, then neutral ligands in alphabetic order and the formula of the whole complex ion is enclosed in square brackets.

Geometry of complexes:

The geometry of complexes depend upon the type of hybridization taking place in the
valence shell of the central metal atom. (Hi) The complex may absorb some of it and may reflect or transmit the remaining light.


When light is allowed to fall on a substance, it absorbs from it the light of a particular colour whose wavelength is in the visible region (4000-7000A) and reflects the remaining light which has the colour complementary to that of the absorbed light. The complementary colour which is actually the colour of reflected light becomes the
colour of the substance.

Every ion absorbs a different wavelength and transmits the remaining set of wavelengths that gives different colours to the ions.

Absorption of yellow light by [Ti(H20)5] 3+ ion. In [Ti(H20)6] 3+ , yellow light is absorbed, while most of the blue and red lights are transmitted, therefore the solution of [Ti(H20)61 3+ ions look violet in colour.

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