les 1 part : 2

[مستر محمد طلعت]

2- The number of known elements until now are 116 elements, 92 elements are abundant in
The earth’s crust, the rest of the elements are prepared artificially.

3-Elements of (A) groups lie on the left and right of the table; you can locate their position.in the modern periodic table by knowing their atomic numbers and vice versa.

4-The elements of ( groups lie in the middle of the table.

Determination the position of element in the table:
1-Number of period of the element = Number of energy levels.
2-Number of the group of the element = Number of electrons in the outermost energy level.