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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?
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उत्तर
(a) The average atomic mass of elements A and C = `(7+39)/2=46/2=23`
(b) The average atomic mass of elements A and C is equal to the atomic mass of element B.
(c) A is lithium, B is sodium and C is potassium.
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संबंधित प्रश्न
An element 'X' belong to 3rd period and group 13 of the Modern Periodic Table.
(a) Determine the valence electrons and the valency of 'X'.
(b) Molecular formula of the compound formed when 'X' reacts with an element 'Y' (atomic number = 8).
(c) Write the name and formula of the compound formed when 'X' combines with chlorine
List any two properties of the elements belonging to the first group of the modern periodic table.
Define the term : Valency
How do the valency and the atomic size of the elements vary while going from left to right along a period in the modern periodic table?
Write the number of horizontal rows in the modern periodic table. What are these rows called?
Which element has a total of two shells, with three electrons in its valence shell?
Name the element which is in seventeenth group and second period.
How does the electropositive character of elements change on going down in a group of the periodic table?
How do atomic structures (electron arrangements) change in a period with increase in atomic numbers from left to right?
In which part of a group would you separately expect the elements to have the largest atomic size?
Given alongside is a part of the periodic table. As we move vertically downward from Li to fr?
| Li | Be |
| Na | |
| K | |
| Rb | |
| Cs | |
| Fr | |
| rA | Ra |
What happens to the size of atoms?
The element which has the maximum number of valence electrons is:
(a) Na
(b) P
(c) Si
(d) A
Periodicity is observed due to the similar ______.
What is its atomic number?
An element X belong to 4th period and 17th group, state.
name of the element.
An element barium has atomic number 56. Look up its position in the periodic table and answer the following question.
Is it more or less reactive than calcium?
Which element has:
twice as many electrons in its second shell as in its first shell?
Name the element in period 3 which does not form oxide.
Calculate the valency of element X whose atomic number is 9.
Atomic number of metal ‚A‛ is 11, while atomic number of metal ‚B‛ is 20. Which of them will be more reactive? Write the chemical reaction of dilute HCl with metal ‚A‛.
Study the extract of the Periodic Table given below and answer the questions that follow. Give the alphabet corresponding to the element in question. DO NOT repeat an element. 
The ion of which element will migrate towards the cathode during electrolysis?
How many groups and periods are there in the modern periodic table?
State the number of elements in period 1, period 2 and period 3 of the periodic table.
What is the common feature of electronic configurations of the elements at the end of period 2 and period 3?
What is meant by a group in the periodic table?
Arrange the following as per instruction given in the bracket.
Cl, F, Br, I (increasing electron affinity)
Arrange the following as per instruction given in the bracket.
K, Pb, Ca, Zn (increasing reactivity)
Arrange the following in order of increasing radii:
N, O, P
The elements of one short period of the periodic table are given below in order from left to right:
| Li | Be | B | C | O | F | Ne |
Which one of the above elements belongs to the halogen series?
With reference to the variation of properties in the Periodic table, which of the following is generally true?
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 |
Which type of ion will be formed by elements A, B, and C.
Element P has atomic number 19. To which group and period, does P belong? Is it a metal or a non-metal? Why?
An element belongs to the third period and Group IIIA (13) of the periodic table. State: if it is a metal or non-metal?
An element A has 2 electrons in its fourth shell. State:
its valency
State the property trends in general of elements on moving down in a group of the periodic table.
State the following:
The group which contains highly electropositive metals including sodium.
Complete the table pertaining to the following elements given in Column I.
| Column I Elements | Atomic Number | Electronic Configuration | Underline the element present in that group |
| 1. Hydrogen | 1 | ______ | Be/Na/Ca |
| 2. Carbon | 6 | ______, ______ | N/P/Si |
| 3. Nitrogen | 7 | _______, ______ | C/P/S |
| 4. Oxygen | 8 | _______, ______ | N/S/Cl |
| 5. Sulphur | 16 | _____, ______, _______ | O/N/F |
| 6. Chlorine | 17 | _____, ______, ______ | I/O/S |
Electron Affinity is maximum in ______.
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?
