CHEMISTRY PROJECT

Question
1. How can the block and period be found out from the subshell electronic configuration of an element?

Answers
In the subshell electronic configuration, the subshell in which the last electron enters is the block of the element. The name of the last subshell, when the subshell electronic configuration written in the ascending order of energy, is the name of the block.

Question
2. Write the relation between the subshell electronic configuration of element in s,p and d block and the group number.

Answers
s-block:- group number is the number of last s electron

p- block:-group number is obtained when 10 is added to the number of last (s+P)electrons.

d- block:-group number is the sum of the last s electron and the d electron in the penultimate shell.

Question
An element exhibits only +2 oxidation state, predict the block and group of this element.

Answers
Block-s, group 2

Question
The electronic configuration of the outermost shell of an element is 3s² 3p²
a. What is the period of the element?
b. What is the group number?

Answers
a. 3 b. group 14

Question
5. In the p-block, though electronegativity increases when moved towards right in the period, this order is not kept in the last element. Examine this statement and write the reason.

Answers
Electronegativity increases because when moved towards right in the period in the p block, the size of the atom decreases. But in the case of the last element in the period as it is an inert gas electronegativity is considered zero as it has no ability to accept the electron pair.

Question
6. Which are not the properties of d block elements?
a. Stable oxidation state
b. Coloured compounds
c. Similarity only in groups
d. Similarity is shown in periods
e. Variable oxidation state
f. Metallic property

Answers
a and c

Question
7. The electronic configuration of an element is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d³
a. Predict the block, period and group of the element.
b. Write the electronic configuration of the element just before this element and of the element just after this element.

Answers
a. Block –d , period – 4, Group – 5
b.Element just before - 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d² Element just before - 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵

Question
8. It is found that a metallic element forms two chloride salts with different colours.
a. what is the assumption about the block of the element?
b. what are the metallic ions of both chlorides? Why?

Answers
a. d block
b. valency of ions will be different. The reason for this is the loss of last electron in the last shell or loss of another electron also from the ‘d’ shell of the penultimate shell.

Question
9. The electronegativity values of the atoms of Mg,O,F are respectively 1.2, 3.5 and 4.
a. predict the chemical bond in the compounds formed when Oxygen combines with Magnesium(Mg), and also with Fluorine(F). Write the reason for this.
b. In the oxygen molecule formed by the combination of Oxygen atoms the bonding is completely covalent. Why?

Answers
a. Ionic bond is formed when O2 combines with Mg to produce (MgO) and covalent bond is formed when it combines with fluorine(OF2). The electronegativity difference between Mg and O is 2.3 and with O and F is 0.5. If the difference is more than 1.7,it will be ionic and if the difference is less than 1.7 it will be covalent.
b. As there is no electronegativity difference between the ‘O’ atoms in the O2 molecules, the bonding will be completely covalent.

Question
10. In a period ionisation energy increases as we move from left to right.
a.In a period the number of shells are equal in atoms of the elements. Then what is the reason for the difference in ionisation energy?
b.what is the change in ionisation energy in groups?
c.The element with least ionisation energy will be the most reactive. Why?

Answers
a. Even though the numbers of shells are equal, as the nuclear charge increases the size ofthe atom decreases. Hence the ionisation energy decreases.
b. In groups as we go down the ionisation energy decreases.
c. Ionisation energy becomes the least means that the electrons in the outermost shell are easily replaceable. That is the electropositive nature or metallic nature increases.

Question
11. Look at the properties of an element

It makes coloured compounds.

Shows variable oxidation states.

It is a metal.

a. To which block does the element belong to?
b. What is the reason for showing variable oxidation states?

Answers
a. ‘d’
c. There is only a slight difference in the energy between the ‘s’ subshell electrons and ‘d’ subshell electrons in the penultimate shell. Therefore during compound formation electrons from ‘s’ subshell or electrons from ‘s’ and ‘d’ may be transferred or shared. Hence the element shows variable valency.

Question
12. Correct wrong statements if found any from those given below.
a.when the difference in electronegativity increases, the possibility of covalent bonding increases. b.electronegativity increases while moving from left to right along a period. c.ionic bond is present in HCl molecule. d.partial ionic bond is also there in polar molecule.

Answers
a.when the difference in electronegativity increases, the possibility of ionic bonding increases.
c.polar covalent bond is present in present in HCl molecule.

Question
13. Equal amount of NaOH solution is added to aqueous solutions of ferric sulphate and ferrous Sulphate taken in two different test tubes. Precipitates of two different colours can be seen in these test tubes.
a. Which compounds are responsible for different colours?
b. Write the subshell electronic configuration of ferric ion.
(Hint: atomic number of iron-26)
c. Why do iron form compounds with two different valencies?

Answers
a. Ferrous hydroxide and ferric hydroxide formed are responsible for the different colours.
b.1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵
c. Iron is a d block element. The energy difference between the‘s’ subshell of the Outermost shell and the ‘d’ subshell of the penultimate shell in d block elements is very small. Therefore during compound formation electrons from both these subshells may be transferred or shared. Hence iron forms compounds with two different valencies.

Question
14. The electronic configuration of chromium is [Ar] 3d⁵ 4s¹
a. what is its atomic number?
b. write the electronic configuration of the atom just before chromium.

Answers
a. 24
b.[Ar] 3d³ 4s²

Question
15. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹. why this electronic configuration is more stable?
Electronic configuration with half filled d subshell (d⁵) orcompletely filled (d¹⁰) d subshell are more stable.

Answers

Question
16. Which are the subshells in which electrons are filled in the s block elements of the third period? Write the subshell electronic configuration of the last element of this period.

Answers
1s 2s 2p 3s
1s² 2s² 2p⁶ 3s² 3p⁶

Question
17. When the last electron of an atom was filled in the 3d subshell, the subshell electronic configuration was recorded as 3d⁸. Answer the questions related to this atom.
a. complete subshell electronic configuration
b. atomic number
c. block
d. period number
e. group number

Answers
a. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁸
b. 28
c. ‘d’ block
d. period-4
e. group 10

Question
18. pick out the wrong ones from the subshell electronic configurations given below:
a. 1s² 2s² 2p⁷
b. 1s² 2s² 2p²
c. 1s² 2s² 2p⁵ 3s¹
d. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s¹
e. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s¹

Answers
a, c , d

Question
19. The element X in group 17 has 3 shells. if so,
a. write the subshell electronic configuration of the element.
b. write the period number
c. what will be the chemical formula of the compound formed if the element X reacts with the element Y of the third period which contains one electron in the p subshell?

Answers
a. 1s² 2s² 2p⁶ 3s² 3p⁵
b. 3
c. YX₃

Question
20. The element Cu with atomic number 29 undergoes chemical reaction to form an ion with oxidation number +2
a. write down the subshell electronic configuration of this ion.
b. can this element show variable valency? why?
c. write down the chemical formula of one compound formed when this element reacts with chlorine (17cl).

Answers
a. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹
b. it can. During chemical reactions it can donate 4s electrons alone or 3d electrons also.
c. CuCl₂

Question
21. certain subshells of an atom are given below.
2s, 2d, 3f, 3d, 5s, 3p
a. which are the subshells that are not possible?
b. give the reason.

Answers
a. 2d, 3f
b. d subshell begins from 3rd shell and f subshell begins from 4th shell.

Question
22. y is an element of the periodic table. its atomic number is 17. complete the following:
a. subshell electronic configuration
b. Group number : ----------
c. period Number : ------------
d. Valency : ------------

Answers
a. 1s² 2s² 2p⁶ 3s² 3p⁵ b. 17 d. 3 e. 1

Question
23. Certain subshell electronic configuration are given below. which of them are wrong and why?
2s³ 2d¹⁰ 3f¹⁴ 4f² 2p² 2s² 3d⁶ 3p⁷

Answers
2s³ the subshell can accommodate a maximum of 2 electrons.
2d¹⁰ the second energy level of subshell is absent
3f⁴ the third energy level of subshell is absent
3p⁷ p subshell can accommodate a maximum of 6 electrons

Question
24. The atomic number of the element X is 19.
a. Write down the subshell electronic configuration of the element X.
b. To which period, group and block does this element belong?
c. what is the oxidation state of this element?
d. The element y has valency 2. what is the chemical formula of X and Y when they combine together ?

Answers
a. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
b.period-4, group-1, s-block
c.+1 oxidation state
d.X₂Y

SELF-ASSESSMENT

1. The electronic configuration of one of the elements given below is wrong. Which is wrong and why?
a. 1² 2s² 2p⁶ 3s¹
b. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d²
c. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s²
d. 1s² 2s¹

2. The electronic configuration of the outermost shell of an element is 3d5 4s1. Which among the following is its atomic number?
21, 26, 24, 29

3. MnO₂, MnCl₂, Mn₂O₃, Mn₂O₇. Among them in which compound the Manganese ion has the electronic configuration.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ ?

4. The subshell electronic configuration of an element is [Ar]3d⁶ 4s²
a. Find out the group of this element.
b. Write 2 properties of this type of element.

5. The atomic number of an element is 33.
a. Write the subshell electronic configuration of this element.
b. Write the block and group of this element.

6. Subshell electronic configuration of some elements is given below.
a. [Ne] 3s²
b. [Ne] 3s² 3p⁴
c. [Ne] 3s² 3p⁵
d. [Ar] 3d⁵ 4s¹

i) Which element shows the highest metallic character?
ii) Which element has the highest electronegativity?
iii) Which element comes in d-block?
iv) Which element comes in the 16th group?

7. Analyse the following table and answer the questions.

Element Atomic Number Electronic Configuration

Na 11 1s² 2s² 2p⁶ 3s¹

K 19 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

Fe 26 [Ar] 3d⁶ 4s²

a. identify the transition element
b. identify the element with larger atomic size
c. From the table, identify the element having greater ionisation energy and justify your answer.

Element	Atomic Number	Electronic Configuration
Na	11	1s² 2s² 2p⁶ 3s¹
K	19	1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
Fe	26	[Ar] 3d⁶ 4s²

Sample Work sheets

Question
1. A section of the periodic table is given a( symbols of elements are not real)

A B

C D
2,8,7

a. Write the electronic configuration of B and C.
b. Find the atomic number of A and C
c. Which of the elements have the same valency? What are their valencies?
d. An element X has Valency 1. Write the chemical formula of the compound formed by the combination of X with A and B.

Answers
a. B- 1s² 2s² 2p⁵ (2,7) c- 1s² 2s² 2p⁶ 3s² 3p⁴ (2, 8, 6)
b. A=8 ; C=16
c. A and C have same valency2 ; B and D have same valency 1
d. XA ; X2B

A	B
C	D 2,8,7

Question
2. A part of the periodic table is given. The symbols of elements given in the columns are not real.

1. Which are the elements having only one electron in the 4s subshell?
2. Which is the element in s block having the least atomic radius?
3. Which are the elements that are likely to make coloured compounds?
4. Which is the most reactive metal?
5. Which is the least reactive element?
6. Which is the element that fills the electron in the 4p subshell?

Answers
1. E, A 2. E 3. D, C 4. A 5. F 6. H

Question
3. Column A contains the character of element and B shows group number and C shows ionisation energy. Find the correct relation.

Answers

Question
4. A section of the periodic table is given below:

a. Which element has the configuration 3d3 4s2 in the last two subshells?
b. Which is the largest atom in group 1?
c. Which element has the highest ionisation energy?

Answers
a. M b. L c. D J

Question
5. The subshell electronic configuration of elements P, Q, R, S , T , E are given below. (symbols of elements are not real )

P 1s² 2s² 2p⁶ 3s¹
Q 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹
R 1s² 2s¹
S 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
T 1s² 2s² 2p⁶ 3s² 3p
E 1S² 2S² 2P⁵

A. Tabulate the elements into s,p,d blocks.
B. which elements belongs to same group?
c. which elements belong to the same period?
d. Name two elements that react intensively?

Answers

Question
7. Match the following :

Element Atomic Number Electronic Configuration Valency

A 14 1s² 2s² 2p⁶ 3s² 3p⁴ 4

B 13 1s² 2s² 2p⁶ 3s² 3p⁵ 2

C 16 1s² 2s² 2p⁶ 3s² 3p¹ 3

D 17 1s² 2s² 2p⁶ 3s² 3p¹ 1

Answers

Element Atomic Number Electronic Configuration Valency

A 14 1s² 2s² 2p⁶ 3s² 3p² 4

B 13 1s² 2s² 2p⁶ 3s² 3p¹ 2

C 16 1s² 2s² 2p⁶ 3s² 3p⁴ 3

D 17 1s² 2s² 2p⁶ 3s² 3p⁵ 1

Element	Atomic Number	Electronic Configuration	Valency
A	14	1s² 2s² 2p⁶ 3s² 3p⁴	4
B	13	1s² 2s² 2p⁶ 3s² 3p⁵	2
C	16	1s² 2s² 2p⁶ 3s² 3p¹	3
D	17	1s² 2s² 2p⁶ 3s² 3p¹	1

Element	Atomic Number	Electronic Configuration	Valency
A	14	1s² 2s² 2p⁶ 3s² 3p²	4
B	13	1s² 2s² 2p⁶ 3s² 3p¹	2
C	16	1s² 2s² 2p⁶ 3s² 3p⁴	3
D	17	1s² 2s² 2p⁶ 3s² 3p⁵	1

Question
8. Complete the following table :

Element X Y

Electronic Configuration 3p⁶ 3d⁶ 4s²

Complete subshell electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶
--------------------- 1s² 2s² 2p⁶ 3s² 3p⁶3d⁶ 4s²
---------------------

Atomic number 18
------- 26
-------

Group 18
------- 8
-------

Block P
------- d
-------

Question
9. Hints about two elements A and B are given below. Answer the given questions based on these hints.
A 3^rd period , 17^th group
B period-3, Group – 13
a. How many number of shells are present in A and B?
b. Write down the subshell electronic configuration of elements A and B.
c. Write the chemical bond formed when A and B combine? Write its formula.

Answers
a. 3 shells
b. A- 1s² 2s² 2p⁶ 3s² 3p⁵
B-1s² 2s² 2p⁶ 3s² 3p¹
c. Ionic bond; formula – BA₃

Question
10. The outermost electronic configuration of elements are given below. Analyse the table and match them suitably:

A B

(1) 4s¹ The elements that produces coloured compounds

(2) 3p⁵ Metal

(3) 3s² Non-metal

(4) 3d⁶ The element that has largest atom

Answers

A B

(1) 4s¹ The element that has largest atom

(2) 3p⁵ Non-metal

(3) 3s² Metal

(4) 3d⁶ The elements that produces coloured compounds

Do it yourself…………………
Examine the table and answer the questions given below. The symbols of elements given in the columns are not real.

1. The inert gas that has d subshell.
2. The name of the group containing A, C.
3. The element in which the electronic configuration ends in 3s2. Name the element. Is it a metal or non-metal?
4. Which is more reactive among B and C?
5. Difference in the blocks of D and E
6. Difference in the subshell electronic configuration of E and F.
7. Similarities in the subshell electronic configuration of F and G.
8. Elements whose d- subshell is completely full.
9. Electronic configuration of the element I.
10. The element whose electronic configuration ends in P4.
11. Member of the halogen group.
12. Among L,M and N which has the greatest electronegativity? Why?

Element	X	Y
Electronic Configuration	3p⁶	3d⁶ 4s²
Complete subshell electronic configuration	1s² 2s² 2p⁶ 3s² 3p⁶ ---------------------	1s² 2s² 2p⁶ 3s² 3p⁶3d⁶ 4s² ---------------------
Atomic number	18 -------	26 -------
Group	18 -------	8 -------
Block	P -------	d -------

A	B
(1) 4s¹	The elements that produces coloured compounds
(2) 3p⁵	Metal
(3) 3s²	Non-metal
(4) 3d⁶	The element that has largest atom