Advertisements
Advertisements
प्रश्न
Calcium is an element with atomic number 20. Stating reason, answer each of the following questions:-
(i) Is calcium a metal or a non-metal?
(ii) Will its atomic radius be larger or smaller than that of potassium with atomic number 19?
(iii) Write the formula of its oxide.
उत्तर
(a) The atomic number of calcium is 20. Its electronic configuration is 2, 8, 8, 2. The valency of calcium is 2; therefore, it is a metal belonging to the group 2 of the periodic table.
(b) Atomic numbers of potassium and calcium are 19 and 20, respectively. Both the elements lie in the third period of the periodic table. Potassium lies to the left of calcium in the period. We know that on moving left to right across a period, the atomic radius of the atom decreases. This happens because of the increase in the force of attraction by the nucleus on going left to right in the period.
(c) The oxide of calcium is calcium oxide and its chemical formula is CaO.
APPEARS IN
संबंधित प्रश्न
How does the size of atoms (atomic size) generally vary in going from left to right in a period of the periodic table? Why does it vary this way?
Complete the following sentences
The similarities in the properties of a group of elements are because they have the same …………………
Taking into consideration the period of the elements given below, answer the following questions:
| Elements | Atomic Radius (pm) |
| O | 66 |
| B | 88 |
| C | 77 |
| N | 74 |
| Be | 111 |
| Li | 152 |
- Arrange the above elements in decreasing order of their atomic radii.
- State the period to which the above elements belong.
- Why this arrangement of elements is similar to the above period of modern periodic table?
- Which of the above elements have the biggest and the smallest atom?
- What is the periodic trend observed in the variation of atomic radius while going from left to right within a period?
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?
Consider the section of the periodic table given below :
| Group numbers |
IA | IIA | IIIA | IVA | VA | VIA | VIIA | O |
| 1 | 2 | 13 | 14 | 15 | 16 | 17 | 18 | |
| Li | D | O | J | Ne | ||||
| A | Mg | E | Si | H | K | |||
| B | C | F | G | L |
With reference to the table, answer the following :
(i) Which is the most electro negative ?
(ii) How many valence electrons are present in G ?
(iii) Write the formula of the compound between B and H ?
(iv) In the compound between F and J, what type of bond will be formed ?
(v) Draw the electron dot structure for the compound formed between C and K.
Choose the word or phrase from the bracket which correctly complete each of the following statement:
Metals are good ................. (oxidising agents/reducing agents) because they are electron ............. (acceptors/donors).
Answer the following question:
State the four blocks of the modern periodic table based on the electronic configuration of elements.
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.
Fill in the blanks from the words A to F given below’.
A: Decreases
B: Increases
C: Remains same
D: Increases by one
E: Electropositive
F: Electronegative
Across a period from left to right in the Modern Periodic Table.
No. of electron shells _________; No. of valence electrons __________: Electronegativity increases Character of elements changes from electropositive to ________.
