In This part we will study : 2. Moseley's periodic table :
In 1913:
The English scientist Moseley discovered, after studying X-rays properties , that the periodicity properties of elements are related to their atomic numbers and not to their atomic weights as Mendeleev believed.
The New Zealand scientist Rutherford discovered that the nucleus of the atom contains positively charged protons
The most important modifications of Moseley on Mendeleev's table :
1. He arranged elements in an ascending order according to their atomic numbers , where the atomic number of each element increases by one from the preceding element in the same period.
2. He added zero (0) group which includes inert (noble) gases to the table.
3. He specified a place below the table for lanthanides and actinides elements .
3. Modern periodic table :
The recent studies led to the identification of the accurate composition of the atoms, where :
- The Danish scientist Bohr had discovered the main energy levels of the' atom and their number reaches 7 in the heaviest atoms known till now.
- Scientists had discovered that each main level contains a definite number of other levels known as energy sublevels, they reclassified the elements in a table known as "Modern periodic table".
- Elements are classified in the modern periodic table in an ascending order according to :
• their atomic numbers .
• the way of filling the energy sublevels with electrons .
لينك تحميل الملزمة :
Prep.2 - unit One - lesson One - First Term 2020
تم شرح هذا الدرس في (3) فيديوهات شاهدها بالترتيب
Attempts of elements Classification
(Part (1/3
(Part (2/3 تشاهده الان
(Part (3/3
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