Advertisements
Advertisements
प्रश्न
Elements in the same group show the same valency. Give scientific reason.
Advertisements
उत्तर
(a) The number of valence electrons in the outermost shell of an atom of an element is equal to the valency of an element.
(b) The number of valence electrons for all the elements in a group is the same. Therefore, the elements in the same group have the same valency.
(c) For example, the elements of Group I such as sodium (Na) and potassium (K) contain only one valence electron, and so, the valency of elements of Group I is one. Similarly, for Group II, the valency is two.
APPEARS IN
संबंधित प्रश्न
Write the electronic configuration of K and Ne.
Two elements ‘P’ and ‘Q’ belong to the same period of the modern periodic table and are in Group 1 and Group 2, respectively. Compare their following characteristics in tabular form:-
(a) The number of electrons in their atoms
(b) The sizes of their atoms
(c) Their metallic character
(d) Their tendencies to lose electrons
(e) The formula of their oxides
(f) The formula of their chlorides
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.
Which element has a total of two shells, with three electrons in its valence shell?
The following table shows the electronic configuration of the elements W, X, Y, Z:
| Element | w | x | y | z |
| Electronic configurations |
2, 8, 1 | 2, 8, 7 | 2, 5 | 1 |
Answer the following questions based on the table above:
1) What type of Bond is formed between :
a) W and X
b) Y and Z
2) What is the formula of the compound formed between :
a) X and Z
b) W and X
How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?
An element X belongs to group 2 and another element Y belongs to group 15 of the periodic table:
(a) What is the number of valence electron in X?
(b) What is the valency of X?
(c) What is the number of valence electrons in Y?
(d) What is the valency of Y?
Explain how you have arrived at your answers.
How does the atomic size vary on going down from top to bottom in a group of the periodic table? Why does it vary this way?
Five elements A, B, C, D and E have atomic numbers of 2, 3, 7, 10 and 18 respectively. The elements which belong to the same period of the periodic table are:
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E
Which of the following set of elements is written correctly in the order of their increasing metallic character?
(a) Mg, Al, Si
(b) C, O, N
(c) Na, Li, K
(d) Be, Mg, Ca
Why are noble gases placed in a separate group?
An element X belong to 4th period and 17th group, state.
Write the formula of the compound formed when it reacts with `(27)/(13) y `
How does the number of:
valence electrons and
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 elements in period 1.
What is the common feature of the electronic configuration of the elements at the end of period 2, and period 3?
An element 'X' (Atomic number – 20) burns in the presence of oxygen to form a basic oxide.
(a) Identify the element and write its electronic configuration.
(b) State its group number and period number in the Modern Periodic Table.
(c) Write a balanced chemical equation for the reaction when this oxide is dissolved in water.
What will be the valency of an element of atomic number 9 (nine)?
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‛.
What is meant by periodicity of elements?
'In a group, the atomic radii increase with increasing period number', explain this statement and justify it with reference to group 17.
Parts (i) to (v) refer to changes in the properties of elements on moving from left to right across a period of the periodic table. For each property, choose the letter corresponding to the correct answer from the choices (a), (b), (c) and (d).
(i) The non metallic character of the elements:
(a) Decreases
(b) Increases
(c) Remains the same
(d) Depends on the period
(ii) The electro negativity
(a) Depends on the number of valence electrons
(b) Remains the same
(c) Decreases
(d) Increases
(iii) The ionization potential
(a) Goes up and down
(b) Decreases
(c) Increases
(d) Remains the same
(iv) The atomic size
(a) Decreases
(b) Increases
(c) Remains the same
(d) Sometimes increases and sometimes decreases
(v) The electron affinity of the elements in groups 1 to 7:
(a) Goes up and down
(b) Decreases and then increases
(c) Increases
(d) decreases
Choose the correct answer from the choice given:
An element A belonging to Period 3 and Group II will have
Arrange the following as per the instruction given in the bracket
He,Ar,Ne (Increasing order of the number of electron shells)
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: the valency,
Name and state the following with reference to the elements of the first three periods of the periodic table.
Metalloid in Period 3.
Name and state the following with reference to the elements of the first three periods of the periodic table.
Alkaline earth metal in period 3.
An element A has 2 electrons in its fourth shell. State:
is it a metal or non-metal
Name the period which is the shortest period of the periodic table.
Name the elements in the correct order of their increasing atomic numbers present in the first, second, and third short periods of the periodic table.
State which of the elements are –
- metallic
- non-metallic
- noble gases
in each of the periods 2 and 3.
State the property trends in general of elements on moving down in a group of the periodic table.
Name or state following with reference to the element of the first three periods of the periodic table.
The valency of elements in group 1 [I–A].
Name or state following with reference to the element of the first three periods of the periodic table.
A non-metal in period 2 having electronic configuration 2, 6.
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.
