Consider two elements 'X' (Atomic number 17) and 'Y' (Atomic number 20) - Science


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 ?



(i) X belongs to Group 17 and 3rd Period.
    Y belongs to Group 2 and 4th Period.

(iii) X is Chlorine while Y is Calcium.

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2013-2014 (March) Delhi Set 3

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Fill in the blank:

The formulae of chloride of metal M is MCl2. The metal M belongs to ……………. group.

Elements in the same group show the same valency. Give scientific reason.

Write the electronic configuration of K and Ne.

The atomic masses of three elements A, B and C having similar chemical properties are 7, 23 and 39, respectively.

  1. Calculate the average atomic mass of elements A and C.
  2. Compare the average atomic mass with atomic mass of B.
  3. What could the elements A, B and C be?

Name any two elements of group one and write their electronic configurations. What similarity do you observe in their electronic configurations? Write the formula of oxide of any of the aforesaid elements.

Write the atomic numbers of two elements 'X' and 'Y' having electronic configuration 2, 8, 2 and 2, 8, 6 respectively.

Which element has a total of three shells, with four electrons in its valence shell?

Classify the following elements into metals, non-metals and metalliods

As, C, Hg, Mg, S, Si

Match the atomic number 2, 4, 8, 15 and 19 with each of the following

1) A solid non metal belonging to the third period.

2) A metal of valency 1.

3) A gaseous element with valency 2.

4) An element belonging to Group 2

5) A rare gas.

Differentiate between Normal elements and Transition elements.

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 change of moving from left to right in the third period of the periodic table?

How does the electropositive character of elements change on going down in a group of the periodic table?

What happens to the metallic character of the elements as we move from left to right in a period of the periodic table?

 How does the tendency to gain electrons change as we go down in group 17 of the periodic table? Why does it change this way?


Which one of the following does not increase while moving down the group of the periodic table?

Why sodium element of group 1 and chlorine element of group 17 both have valency 1?

Name the type of elements .

two electrons in the outermost orbit - ……………

Complete the following sentences

The similarities in the properties of a group of elements are because they have the same …………………

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.

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‛.

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
  1. Arrange the above elements in decreasing order of their atomic radii.
  2. State the period to which the above elements belong.
  3. Why this arrangement of elements is similar to the above period of modern periodic table?
  4. Which of the above elements have the biggest and the smallest atom?
  5. What is the periodic trend observed in the variation of atomic radius while going from left to right within a period?

'In a group, the atomic radii increase with increasing period number', explain this statement and justify it with reference to group 17.

Arrange the following as per instruction given in the bracket.

Mg, Cl, Na, S, Si (decreasing order of atomic size) 

Arrange the following as per instruction given in the bracket.

Cl, F, Br, I (increasing electron affinity)

Arrange the following as per instruction given in the bracket.

Cs, Na, Li, K, Rb (decreasing electronegativity) 

Arrange the following in order of increasing radii: 

 Mg2+, Mg, Mg

Refering to changes in the properties of elements on moving from left to right across a period of the periodic table. Choose the correct answer. 

The ionization potential : 

 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













Which is larger in size (i) D or E (ii) B or C

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.

Write down the word that will correctly complete the following sentence:

Going across a period left to right, atomic size _____.

An element A has 2 electrons in its fourth shell. State:

is it an oxidising or reducing agent 

(a) Fill in the blanks and rewrite the completed statements: 

(i) ________ group in the periodic table contains elements that are all gases at room temperature. 

(ii) Very fine particles mainly scatter ______ light.

Fill in the blank and rewrite the completed statement:

________ group in the periodic table contains elements that are all gases at room temperature.

Give Scientific Reason:
Atomic size increase down the group.

Answer the following question:
State the four blocks of the modern periodic table based on the electronic configuration of elements.

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 _______.

What is meant by a Group in the Periodic Table?

Name the period which is the shortest period of the periodic table.

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

Down a group in the Modern Periodic Table.
No. of electron shells __________; No. of valence electrons ________; Electronegativity ________ Character of elements changes from _________ to ____________.

Give a reason for the following:

A transition from metallic to non-metallic elements is seen on moving from left to right in a period of the periodic table.

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


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