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प्रश्न
उत्तर
Atomic size increases down the group
- The atomic numbers of the elements increase as we go down the group. Thus, the elements placed lower have more electrons.
- To accommodate these electrons new shells are added to the atom.
- These new shells take the outermost electrons farther from the nucleus causing atomic size (radius) to increase as we go down the group.
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संबंधित प्रश्न
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.
Two elements ‘A’ and ‘B’ belong to the 3rd period of Modern periodic table and are in group 2 and 13, respectively. Compare their following characteristics in tabular form:-
(a) Number of electrons in their atoms
(b) Size of their atoms
(c) Their tendencies to lose electrons
(d) The formula of their oxides
(e) Their metallic character
(f) The formula of their chlorides
From the following elements :
4Be; 9F; 19K; 20Ca
(i) Select the element having one electron is the outermost shell.
(ii) two elements of the same group.
Write the formula of and mention the nature of the compound formed by the union of 19K and element X(2, 8, 7).
Write the atomic numbers of two elements 'X' and 'Y' having electronic configuration 2, 8, 2 and 2, 8, 6 respectively.
Based on the group valency of elements state the formula lot the following giving justification for each :-
(i) Oxides of 1st group elements,
(ii) Halides of the elements of group 13, and
(iii) Compounds formed when an element of group 2 combines with, an element of group 16.
Define the term : Atomic size
Write the number of horizontal rows in the modern periodic table. What are these rows called?
Name the element that has two shells, both of which are completely filled with electrons.
Which element has a total of two shells, with three electrons in its valence shell?
How does the number of valence electrons vary on moving from left or right in the first period of the periodic table?
How does the number of valence electrons vary on moving from left or right in the second period of the periodic table?
How does the valency of elements vary in going down a group of the periodic table?
Fill in the blank in the following statement:
The tendency to gain an electron ............... on moving down in a group of the periodic table.
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.
Why do elements in the same group show similar properties but the elements in different groups show different properties?
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 |
What happens to their metallic character?
In each of the following pair, choose the atom having the bigger size:
Na (At. No. 11) or K (At. No. 19)
Why are noble gases placed in a separate group?
State the valency of the elements of periods 3 and write the formula of their oxides.
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……….
How do the following change on moving from left to right in a period of the periodic table?
Give examples in support of your answer.
Chemical reactivity of elements ?
Write two reasons responsible for late discovery of noble gases ?
An element 'M' has atomic number 12.
(a) Write its electronic configuration.
(b) State the group to which 'M' belongs.
(c) Is 'M' a metal or a non-metal.
(d) Write the formula of its chloride.
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‛.
The following table represents the first period of the modern periodic table. Study the table and answer the questions that follow:
(i) Write the formula of the sulphate of the element with atomic number 13.
(ii) What type of bonding will be present in the oxide of the element with atomic number 1?
(iii) Which feature of the atomic structure accounts for the similarities in the chemical properties of the elements in group VIIA of the periodic table?
(iv) Name the element which has the highest ionization potential.
(v) How many electrons are present in the valence shell of the element with atomic number 18?
(vi) What is the name given to the energy released, when an atom in its isolated gaseous state accepts an electron to form an anion?
(vii) What is the electronic configuration of the element in the third period which gains one electron to become an anion?
(viii) Fill in the blanks:
The atomic size ______ as we move from left to right across the period, because the ______ increases, but the ______ remains the same.
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.
Arrange the following as per the instruction given in the bracket
He,Ar,Ne (Increasing order of the number of electron shells)
Arrange the following as per instruction given in the bracket.
Li, K, Na, H ( decreasing order of their potential ionisation )
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).
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?
Formula of ion of A is A2+. Element A probably belongs to ______ group.
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.
Going across a period left to right, atomic size _____.
What is the common feature of the electronic configuration of the elements at the end of Period 2 and Period 3?
Supply the missing word from those in bracket:
If an element has one electron in its outermost energy level [shell] then it is likely to be _______.
Name the period which is the shortest period of the periodic table.
Electron Affinity is maximum in ______.
Which of the following would weigh the least?
(Atomic masses C = 12, 0 = 16, Na = 23)
