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प्रश्न
Elements in the same group show the same valency. Give scientific reason.
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उत्तर
(a) The number of valence electrons in the outermost shell of an atom of an element is equal to the valency of an element.
(b) The number of valence electrons for all the elements in a group is the same. Therefore, the elements in the same group have the same valency.
(c) For example, the elements of Group I such as sodium (Na) and potassium (K) contain only one valence electron, and so, the valency of elements of Group I is one. Similarly, for Group II, the valency is two.
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संबंधित प्रश्न
Taking the example of an element of atomic number 16, explain how the electronic configuration of the atom of an element relates to its position in the modern periodic table and how valency of an element is calculated on the basis of its atomic number.
How do the atomic size and metallic character of elements vary as we move :-
(a) down a group and
(b) from left to right in a period
Which element has a total of three shells, with four electrons in its valence shell?
Which element has a total of two shells, with three electrons in its valence shell?
Match the atomic number 2, 4, 8, 15 and 19 with each of the following
1) A solid non metal belonging to the third period.
2) A metal of valency 1.
3) A gaseous element with valency 2.
4) An element belonging to Group 2
5) A rare gas.
How does the valency of elements vary in going down a group of the periodic table?
Arrange the following elements in increasing order of their atomic radii:
Li, Be, F, N
Rewrite the following statement after correction, if necessary:
The metallic character of elements in a period increases gradually on moving from left to right.
Fill in the blank in the following statement:
In going across a period (right to left) in periodic table, the atomic size of the atom ...............
The atomic radii of three elements X, Y and Z of a period of the periodic table are 186 pm; 104 pm and 143 pm respectively. Giving a reason, arrange these elements in the increasing order of atomic numbers in the period.
For each of the following triads, name the element with the characteristics specified below:
| Elements | Least atomic radius | Chemically least reactive |
| (i) F, Cl, Br (ii) Li, Na, K |
.................... .................... |
.................... .................... |
In which part of a group would you separately expect the elements to have the greatest metallic character
Explain why, the properties of elements are repeated after 2, 8, 18 and 32 elements in the periodic table.
Five elements A, B, C, D and E have atomic numbers of 2, 3, 7, 10 and 18 respectively. The elements which belong to the same period of the periodic table are:
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E
Where would you locate the element with electronic configuration 2, 8 in the modern periodic table?
What is its atomic number?
An element A has atomic number 14. To which period does this element belong and how many elements are there in this period.
How do the following change on moving from left to right in a period of the periodic table?
Give examples in support of your answer.
atomic structure (electron arrangements) ?
Which element has:
twice as many electrons in its second shell as in its first shell?
State the number of elements in periods 1, Periods 2, and Period 3 of the periodic table. Name them.
name the elements in period 1.
Write two reasons responsible for late discovery of noble gases ?
Calculate the valency of element X whose atomic number is 9.
What is modern periodic law?
Fill in the blank
Oxidising property ________from fluroine to iodine because the power to accpet electron decreases.
Arrange the following in increasing order of property indicated
SiO2, P2O5, SO3, Cl2O7 (acidic nature)
State the number of elements in period 1, period 2 and period 3 of the periodic table.
Name the elements in period 1.
What is the common feature of electronic configurations of the elements at the end of period 2 and period 3?
In the above table, H does not represent hydrogen.Some elements are given in their own symbol and position in the periodic table while others are shown with a letter. With refrence to the table answer the following questions.
1. Identify the most electronegative element.
2. Identify the most reactive element of Group I.
3. Identify the element from Period 3 with least atomic size.
4. How many valence electrons are present in Q?
5. Which element from group 2 would have the least ionisation energy?
6. Identify the noble gas of the fourth period.
7. In the compound between A and H, what type of bond would be formed and give its molecular formula.
Use the letters only written in the Periodic Table given below to answer the questions that follow:
(a) State the number of valence electrons in the atom J.(b) Which element shown forms ions with a single negative charge?
(c) Which Metallic element is more reactive than R?
(d) Which element has its electrons arranged in four shells?
The position of elements A, B, C, D and E in the periodic table are shown below:
|
Group 1 |
Group 2 |
Group 17 |
Group 18 |
|
|
|
|
D |
|
|
B |
C |
|
|
A |
|
|
E |
State which is most reactive (i) metal (ii) non-metal
Name and state the following with reference to the elements of the first three periods of the periodic table.
Metalloid in Period 3.
(a) Fill in the blanks and rewrite the completed statements:
(i) ________ group in the periodic table contains elements that are all gases at room temperature.
(ii) Very fine particles mainly scatter ______ light.
The electronic configuration of an element is 2, 8, 4. State it:
group and period in the Modern Periodic Table.
The electronic configuration of an element is 2, 8, 4. State it:
name and write its one physical property.
State the property trends in general of elements on moving from left to right in a period of the periodic table.
Select the correct answer from the options given below.
It is a metal in period 2 having electronic configuration 2, 1?
Chlorine in the Periodic Table is surrounded by the elements with atomic number 9, 16, 18 and 35.
Which of these have Physical and Chemical properties resembling chlorine?
