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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.
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संबंधित प्रश्न
Fill in the blank:
The formulae of chloride of metal M is MCl2. The metal M belongs to ……………. group.
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
The atomic numbers of the elements Na, Mg, K and Ca are 11, 12, 19 and 20 respectively. The element having the largest atomic radius is:
(a) Mg
(b) Na
(c) K
(d) Ca
What do you understand by periodicity?
How does the number of:
valency vary on moving from left to right in the second period of the periodic table?
How can the valency of an element be determined if its electronic configuration is known?
Fill in the blank
Oxidising property ________from fluroine to iodine because the power to accpet electron decreases.
Atomic number of an element is 16. State
- the period to which it belongs
- the number of valence electrons
- whether it is a metal or non-metal
Write the electronic configuration of two elements A and B whose atomic numbers are 20 and 17 respectively. Write the molecular formula of the compound formed when element A reacts with element B. State whether this compound is acidic, basic or neutral. Give a reason to justify your answer.
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 ________.
