Page 7 - E-Science Prep.2 2024-2025 t1 Unit1_Neat
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3- Modern periodic table
? It was after the scientists discovered that each main
level consists of definite number of sublevels.
? In modern periodic table, elements are classified
according to:
1- Atomic number of elements
2- The way of filling the energy sublevels with electrons.
Description of modern periodic table:
? It includes 118 elements.
(92 elements are abundant in earth’s crust and the
rest are prepared artificially)
? it consists of:
- 7 horizontal periods
- 18 vertical group.
? Elements are classified into 4 blocks (s, p, d and f)
s-block elements d- block elements p- block elements
-They are found in the middle of
-They are found theperiodic table. -They are found
onthe left side of -They are arranged in 8 groups on the right side
the (3B),(4B),(5B),(6B),(7B),(8),(1B) of theperiodic
and(2B). table.
periodic table. -They are known as -They are 6 groups
transitionalelements (3A),(4A),(5A),(6A)
-They are 2 -They start appearing in period(4) (7A) and zero group
groups
(1A) and (2A).
f-block elements
-are located below the periodic table
-include lanthanides and actinides
2nd Prep. First Term 7
