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प्रश्न
Write scientific reason.
The third period contains only eight elements even though the electron capacity of the third shell is 18
उत्तर
The third period contains only eight elements even though the electron capacity of the third shell is 18 because there are 10 electrons which are found to have higher energy than the remaining 8 electrons. The universe prefers the path of less energy. The energy of these 10 electrons is equivalent to the energy of the 4th shell electron. That’s why these electrons are not counted in 3rd shell.
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संबंधित प्रश्न
An element has its electron configuration as 2, 8, 2. Now answer the following question.
a. What is the atomic number of this element?
b. What is the group of this element?
c. To which period does this element belong?
d. With which of the following elements would this element resemble? (Atomic numbers are given in the brackets)
N(7), Be(4), Ar(18), Cl(17)
Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
3Li, 14Si, 2He, 11Na, 15P Which of these elements belong to be period 3?
Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
4Be, 6C, 8O, 5B, 13Al Which is the most electropositive element among these?
Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
19K, 3Li, 11Na, 4Be Which of these atoms has smallest atomic radius?
An element has its electron configuration as 2, 8, 2. Now answer the following question.
What is the atomic number of this element?
_______ is the outermost shell for elements of period 2.
Write the name of an element having electronic configuration 2,8,2.
What determines the chemical reactivity of elements?
Match the columns.
| Column A | Column B |
| Electronic configuration |
Valency |
| 1) 2, 2 | a) 1 |
| 2) 2, 8, 1 | b) 2 |
| 3) 2, 5 | c) 3 |
| d) 5 |
Write the name.
The group of elements having electronic configuration 2, 2.
The valency of the elements in group 2 is 1.
The number of shells decreases in a group from top to bottom.
Write an Explanation.
Group
Find the period in which these elements can be placed.
4Be, 17Cl, 2He, 13Al
Distinguish between:
Group - Period
Identify periods of elements and blocks of elements from given electronic configuration?
- 2, 8, 2
- 2, 8, 7
- 2, 1
Observe the given chart and answer the questions given below.
| Element | A | B | C | D |
| Electronic configuration | 2, 1 | 2, 8 | 2, 8, 1 | 2, 8, 8 |
- Which elements are in the same row?
- Which elements have the same column?
- Which elements are in the 18th column?
- Which element is more reactive among A and C?
- Which of the following elements A or B will form compounds?
Make a chart which shows the name of the element, valency, atomic number, electronic configuration in the 2nd row of the modern periodic table and arrange these elements in ascending order of atomic mass.
What is the electronic configuration of K19?
