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Question
An element A has 2 electrons in its fourth shell. State:
its atomic number
Solution
Its atomic number is 20.
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RELATED QUESTIONS
The atomic number of an element is more important to the chemist than its relative atomic mass. Why?
Complete the table:
|
Atomic number |
Element |
Electronic configuration |
Select an element of the same group |
|
11 |
Sodium |
|
(Ca/N/K)… |
|
15 |
Phosphorus |
|
(Ba/N/Rb)… |
|
16 |
Sulphur |
|
(F/Cl/O)… |
|
9 |
Fluorine |
|
(Ca/Cl/K)… |
Relative atomic mass of a light element up to calcium is approximately ______ its atomic number.
What is meant by ‘period number’. What does it signify?
In Modern Periodic Table the number of columns and periods are respectively _______ and _______.
Modern periodic law states that the physical and chemical properties of elements are the periodic functions of their ______.
State whether true or false. If false, correct the statement.
Newlands’ periodic table is based on atomic masses of elements and modern periodic table is based on atomic number of elements.
State modern periodic law.
The basis of modern periodic law is ______.
| Group in the modern periodic table | Families |
| 1 | ______ |
| ______ | Transition metals |
| ______ | Boron family |
| 15 | ______ |
| 17 | ______ |
