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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
The atomic masses of three elements A, B and C having similar chemical properties are 7, 23 and 39, respectively.
- Calculate the average atomic mass of elements A and C.
- Compare the average atomic mass with atomic mass of B.
- What could the elements A, B and C be?
Which element has twice as many electrons in its second shell as in its first shell?
An element with the atomic number 19 will most likely combine chemically with the element whose atomic number is ______.
Calculate the mass of Calcium that will contain the same number of the atom as are present in 3.2 gm of Sulphur.
[Atomic masses: S=32, Ca=40]
How does the valency of elements change of moving from left to right in the third period of the periodic table?
Name the element which is in seventeenth group and second period.
How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?
Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
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 |
.................... .................... |
.................... .................... |
State one reason for keeping fluorine and chlorine in the same of the periodic table.
In which part of a group would you separately expect the elements to have the greatest metallic character
In terms of electronic configurations, explain the variation in the size of the atoms of the elements belonging to the same period and same group ?
Which of the following element does not lose an electron easily?
(a) Na
(b) F
(c) Mg
(d) Al
Why sodium element of group 1 and chlorine element of group 17 both have valency 1?
Periodicity is observed due to the similar ______.
An element X belong to 4th period and 17th group, state.
Write the formula of the compound formed when it reacts with `(27)/(13) y `
How does the number of:
valence electrons and
An element X belong to 3rd periods and group II of the periodic table state:
the number of valence electrons,
Complete the following sentences.
The properties of the elements are a periodic function of their …………… (atomic number, mass number, reative atomic mass).
Which element has:
twice as many electrons in its second shell as in its first shell?
Write two reasons responsible for late discovery of noble gases ?
K, Pb, Ca, Zn (In the increasing order of the reactivity)
Fill in the blank
Oxidising property ________from fluroine to iodine because the power to accpet electron decreases.
Name the elements in period 1.
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.
Choose the most appropriate answer from the following list of oxides which fit the description.
A basic oxide.
Choose the most appropriate answer from the following list of oxides which fit the description.
An amphoteric oxide: Al2O3 (shows both acidic and basic properties)
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?
Formula of ion of A is A2+. Element A probably belongs to ______ group.
An element belongs to the third period and Group IIIA (13) of the periodic table. State: the number of valence electrons,
The electronic configuration of an element is 2, 8, 4. State it:
group and period in the Modern Periodic Table.
Name the elements in the correct order of their increasing atomic numbers present in the first, second, and third short periods of the periodic table.
State which of the elements are –
- metallic
- non-metallic
- noble gases
in each of the periods 2 and 3.
State the property trends in general of elements on moving down in a group of the periodic table.
Name or state following with reference to the elements of the first three periods of the periodic table.
The number of electron shells in elements of period 1, period 2, and period 3.
Name or state following with reference to the element of the first three periods of the periodic table.
A metal in period 3 having valency 3.
Select the correct answer from the options given below.
Is the group number of the element whose atomic number is 4.
State the following:
The group to which the element with an electronic configuration of 2, 8, 2 belongs.
