Advertisements
Advertisements
Question
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?
Advertisements
Solution
(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.
APPEARS IN
RELATED QUESTIONS
Fill in the blank:
The formulae of chloride of metal M is MCl2. The metal M belongs to ……………. group.
The elements Be, Mg and Ca each having two electrons in their outermost shells are in periods 2, 3, and 4 respectively of the modern periodic table. Answer the following questions, giving justification in each case:-
(i) Write the group to which these elements belong.
(ii) Name the least reactive element.
(iii) Name the element having largest atomic radius.
An element 'X' has mass number 35 and number of neutrons 18. Write atomic number and electronic configuration of 'X'. Also write group number, period number and valency of 'X'.
Write the atomic numbers of two elements 'X' and 'Y' having electronic configuration 2, 8, 2 and 2, 8, 6 respectively.
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?
Consider two elements 'A' (Atomic number 17) and 'B' (Atomic number 19) :
(i) Write the positions of these elements in the modern periodic table giving justification.
(ii) Write the formula of the compound formed when 'A' combines with 'B.'
(iii) Draw the electron dot structure of the compound and state the nature of the bond formed between the two elements.
Consider two elements 'X' (Atomic number 17) and 'Y' (Atomic number 20)
(i) Write the positions of these elements in the modern periodic table giving justification.
(ii) Write the formula of the compound formed by the combination of 'X' and 'Y'.
(iii) Draw the electron-dot structure of the compound formed and state the nature of the bond formed between the two elements ?
Which element has a total of three shells, with four electrons in its valence shell?
Use the letters only written in the Periodic Table given below to answer the questions that Follow :
1) State the number of valence electrons in atom J.
2) Which element shown forms ions with a single negative charge?
3)Which metallic element is more reactive than R?
4) Which element has its electrons arranged in four shells?
Name the element which is in first group and third period.
How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?
Arrange the following elements in increasing order of their atomic radii:
Li, Be, F, N
Arrange the following elements in the increasing order of their metallic character:
Mg, Ca, K, Ga
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 ...............
How does the electropositive character of elements change on going down in a group of the periodic table?
Why does the size of the atoms progressively become smaller when we move from sodium (Na) to chlorine (Cl) in the third period of the periodic table?
Which one of the following does not increase while moving down the group of the periodic table?
What do you understand by orbits?
How does the number of:
valency vary on moving from left to right in the second period of the periodic table?
Fill in the blank:
on moving from right to left in the second period, the number of valence electrons……….
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?
Complete the following sentences
The similarities in the properties of a group of elements are because they have the same …………………
Name the element which has the electronic configuration 2, 8, 3?
Write two reasons responsible for late discovery of noble gases ?
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‛.
How many groups and periods are there in the modern periodic table?
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)
Select the correct answer
Number of shells in potassium are
Select the correct answer
Identify the metalloid
An element Z has atomic number 16. Answer the following
(a) State the period and group to which Z belongs
(b) Is Z a metal or a non-metal?
(c) State the formula between Z and hydrogen.
(d) what kind of a compund is this?
Arrange the following as per instruction given in the bracket.
K, Pb, Ca, Zn (increasing reactivity)
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.
State the nature of compounds formed when group 17 elements combine with (i) metals (ii) non-metals.
An element A has 2 electrons in its fourth shell. State:
is it a metal or non-metal
Based on the group valency of element write the molecular formula of the following compound giving justification:
Halide of the elements of group thirteen
Name or state following with reference to the element of the first three periods of the periodic table.
The valency of the element in period 3 having atomic number 17.
Name or state following with reference to the element of the first three periods of the periodic table.
A non-metal in period 2 which is tetravalent.
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 |
