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Graduation of representative elements Properties
CHEMISTRY - Secondary 2
In This part we will study:
B- Ionic radius
The ionic compounds as sodium chloride are found in a crystalline form and consist of positive ions (cations) and negative ions (anions).

Ionic bond length: Is estimated by the distance between the centers of the nuclei of two bonded ions.
The ionic bond length = the sum of two ionic radii in the formula unit
• The ionic radius depends on the number of electrons lost or gained to form ions.
Examples

Solution

The effective nuclear charge concept (Z_eff)
The valence electrons are not affected by the complete nuclear charge (the charge of the nucleus protons).
This is because the inner electrons (of the inner energy levels) screen a part of this charge from the valence electrons (electrons under study).

Effective nuclear charge Z_eff: is the actual nuclear charge (positive charge) that affects an electron in an atom.
The graduation of atomic radius in the periodic table
General conclusion:
• The atoms of the first group elements (alkalis) are the biggest atoms, while the atoms of the seventh group elements (halogens) are the smallest atoms.
• The biggest atom in size is cesium (Cs).

The relation between the radii of atoms and their ions
• The radii of atoms differ from the radii of their ions as shown in the following

Example
In the light of your knowledge about the graduation of the atomic radius property in the periodic table:

Best wishes to you
Mr.Ahmed Elbasha

كيمياء الصف الثاني الثانوي لغات - الفصل الدراسي الاول
شرح كيمياء لغات تانية ثانوي - مستر احمد الباشا