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Graduation of representative elements Properties
CHEMISTRY - Secondary 2
In This part we will study:
The chemical properties and some of the physical properties of the elements depend on their electronic configuration and especially on the valence electrons (the electrons of the outermost level).
We will study the graduation of the following properties for the representative elements:
The atomic radius.  Ionization potential.
Electron affinity.  Electronegativity.
Metallic and nonmetallic property.  Acidic and basic property.
Oxidation numbers.

 The atomic radius:
• The concept of bond length in the covalent compounds differs from that in the ionic compounds.
• By knowing the bond length, we can calculate:
(A) Atomic radius.
(B) Ionic radius.

A- Atomic radius
• The atomic radius can't be defined or can't be physically measured by the distance between the nucleus and the farthest electron, because it is impossible to determine the precise location of an electron around the nucleus (as the wave mechanics theory revealed).
But the atomic radius can be calculated by knowing
• The covalent bond length which is measured by Angstrom unit (Å).

Covalent bond length (2r): Is estimated by the distance between the centers of the two nuclei of two bonded atoms.
Atomic radius (r): Is estimated by half the distance between the centers of two similar atoms in a diatomic molecule.
Following table shows the bond length and covalent atomic radius for some molecules:

Examples

 • The bond length in chlorine molecule Cl-Cl is 1.98 Å
• The bond length between carbon and chlorine atoms C - Cl in carbon tetrachloride CCl4 is 1.76 Å
Calculate the atomic radius of carbon.

Solution
 The bond length in hydrogen molecule H - H = 0 .6 Å, the bond length of nitrogen molecule N2 = 1.4 A and the bond length of nitric oxide molecule NO = 1.36 Å
Calculate:
(1) The bond length in oxygen molecule O2
(2) The bond length (O-H) in water molecule H2O

Solution

Best wishes to you
Mr.Ahmed Elbasha

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