ساينس الصف الثاني الاعدادي – الفصل الدراسي الاول ساينس الثاني اعدادي – ترم اول In This part we will study : Description of the modern periodic table : The number of known elements in the modern periodic table till now is 118 elements , 92 elements are abundant (available) in Earth ‘s crust, while the rest are prepared artificially The modern periodic table consists of : – 7 horizontal periods . – 18 vertical groups. – The elements of modem periodic table are classified into 4 blocks (s, p, d and f). 1. S-block elements : They are located on the left side of the periodic table . They are arranged in two groups (IA) and (2A). 2. p-block elements :: They are located on the right side of the periodic table . They are arranged in six groups (3A) , (4A) , (5A) , (6A) , (7A) and zero group . 3. d-block elements : They are located in the middle of the periodic table . They are arranged in eight groups (3B), (4B), (5 B), (6B), (7B ), (8) , (lB) and (2 B). They are known as transition elements . They appear to start from period ( 4) . Note All groups in d-block take letter “B” except group (8), which consists of three vertical columns . 4. f-block elements : They are located below the periodic table . They include lanthanides and actinides . How to locate the position of an element in the modern periodic table : – It is possible to determine the location of elements of group “A” in the modern periodic table by knowing their at9mic numbers; where : • The element period number = number of energy levels occupied by electrons in its atom. • The element group number = number of electrons in the outermost energy level in its atom. لمتابعة مستر احمد الباشا وكل ما يخص الساينس : جروب الفيس بوك http://bit.ly/2Of1mcN صفحة الفيس بوك http://bit.ly/2Gq5xMo بالتوفيق مستر احمد الباشا