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Questions:

Multiple Choice Question

7 x 1 = 7

How does electron affinity change when we move from left to right in a period in the periodic table?

(a)

Generally increases

(b)

Generally decreases

(c)

Remains unchanged

(d)

First increases and then decreases

Which one of the following is true about metallic character when we move from left to right in a period and top to bottom in a group?

(a)

Decreases in a period and increases along the group

(b)

Increases in a period and decreases in a group

(c)

Increases both in the period and the group

(d)

Decreases both in the period and in the group

The First ionisation potential of Na, Mg and Si are 496, 737 and 786 kJ mol^-1 respectively. The ionisation potential of Al will be closer to

(a)

760 kJ mol^-1

(b)

575 kJ mol^-1

(c)

801 kJ mol^-1

(d)

419 kJ mol^-1

The electronic configuration of the atom having maximum difference in first and second ionisation energies is

(a)

1s₂, 2s₂, 2p⁶ 3s¹

(b)

1s², 2s²,2p⁶, 3s²

(c)

1s², 2s²,2p⁶, 3s², 3s², 3p⁶, 4s¹

(d)

Is², 2s²,2p⁶, 3s², 3p¹

The correct order of decreasing electronegativity values among the elements X, Y, Z and A with atomic numbers 4, 8,7 and 12 respectively

(a)

Y > Z > X > A

(b)

Z > A >Y > X

(c)

X > Y > Z > A

(d)

X > Y > A > Z

Identify the wrong statement.

(a)

Amongst the isoelectronic species, smaller the positive charge on cation, smaller is the ionic radius

(b)

Amongst isoelectric species greater the negative charge on the anion, larger is the ionic radius

(c)

Atomic radius of the elements increases as one moves down the first group of the periodic table

(d)

Atomic radius of the elements decreases as one moves across from left to right in the 2nd period of the periodic table

In the third period the first ionization potential is of the order

(a)

Na > Al > Mg > Si > P

(b)

Na< Al < Mg < Si < P

(c)

Mg > Na > Si > P > Al

(d)

Na < Al < Mg < Si < P

Generic 5

2 x 5 = 10

Give the characteristics of p-block elements.

Give the structural features of modern periodic law.

Generic 3

6 x 3 = 18

10.

Explain the size of Cl^- >Na⁺.

11.

Arrange the following elements in the increasing order of non-metallic character. B, C, Si, N, F

12.

Which among the halogens would you expect to have the least electronegativity and why?

13.

Why electron affinity of fluorine is less than that of chlorine?

14.

Arrange the following elements in the increasing order of metallic character: Si, Be, Mg, Na, P.

15.

The elements Z = 117 and 120 have not yet been discovered. In which family/group would you place these elements and also give the electronic configuration in each case.

Generic 2

6 x 2 = 12

16.

Explain about periodic variation of electro negativity across a period.

17.

Electron affinity of oxygen is less negative than sulphur. Justify this statement.

18.

State the Newland's law of octaves.

19.

The element 119 has not been discovered. What would be the IUPAC name and symbol for this element? On the basis of periodic table, predict the electronic configuration of this element

20.

Explain how will you find the atomic number of an element from the frequency of X-rays emitted by an element.

21.

Briefly outline anomalies of Mandeleev's periodic table

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Answers Key:

Multiple Choice Question

7 x 1 = 7

(a)
Generally increases

(a)
Decreases in a period and increases along the group

(b)
575 kJ mol^-1

(a)
1s₂, 2s₂, 2p⁶ 3s¹

(a)
Y > Z > X > A

(a)
Amongst the isoelectronic species, smaller the positive charge on cation, smaller is the ionic radius

(b)
Na< Al < Mg < Si < P

Generic 5

2 x 5 = 10

Characteristics of p-block elements:
(i) General electronic configuration is ns²np^1-6 (Group 13 to 18).
(ii) They are generally non-metals but some metals and metalloids are present.

Non-metallic character increases from left to right along period.
Metallic character increases on moving down a group.

(iii) They have high electron affinity and ionization enthalpy.

Both the properties increase along the period.
Both the properties decrease on moving down the group.

(iv) Oxidising character.

Increases on moving from left to right along a period.
Reducing character increases from top to bottom in a group.

(v) s-block and p-block elements are collectively called representative elements.

(i) According to the recommendation of IUPAC, the groups are numbered from 1 to 181A.
(ii) There are 18 vertical columns which constitute 18 groups or families.
(iii) There are 7 horizontal rows of the periodic table known as periods.
(iv) The first period contains two elements. One present in first group and the other in 18th group.
(v) Second and third periods contain 8 elements in each.
(vi) Fourth and fifth periods are completely filled as they contain 18 elements in each.
(vii) The sixth period contains 32 elements. The seventh is incomplete. Fourteen elements of both sixth and seventh periods are placed in separate panels at the bottom of the table.
(viii) This periodic table is important and useful because we can predict the properties of any element using periodic trend.

Generic 3

6 x 3 = 18

10.

Na⁺ - 10 electrons 1s² 2s² 2p⁶
Cl^- - 18 electrons 1s² 2s² 2p⁶ 3s² 3p⁶
In case of Na⁺ the nuclear charge is more. So the electrons are strongly attracted by the nucleus, nuclear charge so the size decreases.
In CI^- the number of orbital electrons becomes greater, nuclear charge decreases and hence the electrons are not strongly attracted by the nucleus so ionic radius increases.

11.

The increasing order of non-metallic character as follow
Non metallic character increases across the period and decreases down the group.

12.

On moving down the group, electronegativity decreases because atomic size increases. Iodine is the largest, therefore it is least electronegative.

13.

(i) F-1s² 2s² 2p_x² 2p_y² 2p_z¹
Cl- -1s² 2s² 2p⁶ 3s² 3p_x² 3p_y² 3p_z¹
(ii) Because of small size of fluorine, the 2p subshell becomes compact.
(iii) There occurs electron-electron repulsion
(iv) Due to its small size, large crowding of electrons occurs which reduces the nuclear charge. So the electron affinity of fluorine is less than chlorine.

14.

Metallic character increases down a group and decreases along a period as we move from left to right.Hence the order of increasing metallic character is, P < Si < Be < Mg < Na.

15.

The element with Z = 117, would belong to the halogen family (group 17) and the electronic configuration 89 would be. [Rn] 4f¹⁴ 5d¹⁰ 7s² 7p⁵ . the element with Z = 120, will be placed in group 2 (alkaline earth metals), and will have the electronic configuration [Uuo]8s² .

Generic 2

6 x 2 = 12

16.

As we move from left to right in a period, electronegativity increases. This is due to the following reasons:
(a) Nuclear charge increases in a period
(b) Atomic size decrease in a period
Halogens have the highest value of electronegativity in their respective periods.

17.

When an electron is added to oxygen, the added electron goes to the 'L' shell (n = 2). As the 'L' shell possess smaller region of space, the added electron feels significant repulsion from the other electrons present in this level.
E.A of O=-141 KJ mole^-1
E.A of S = -200 KJ mole^-1

18.

The Law of octaves states that, "when elements are arranged in the order of increasing atomic weights, the properties of the eighth element are a repetition of the properties of the first element".

19.

The root's for 1 and 9 are un and enn respectively. Hence, the name of the element with Z = 119 is Un + Un + enn + ium = ununennium. Its symbol isuue.
The atomic number of the last number of the 7th period is 118. Thus, this element will belong to 8th period and will be the first element i.e., alkali metal (8 s').
Its electronic configuration :2, 8, 18, 32, 32, 18, 8, 1

20.

Mosley's relationship is given as \(\sqrt { v } \) = a (Z - b) where v is the frequency of X-rays emitted by an element of atomic number Z.
The plot of IV against Z gives a straight line. Using. this relationship, we can determine the atomic number of an unknown (new) element from the frequency of X-ray emitted.

21.

(i) Some elements with similar properties were placed in different groups and those with dissimilar properties were placed in same group.
eg: Tellurium (127.6) was placed in VI group but Iodine (127.0) was placed in VII group.
(U) Similarly elements with higher atomic weights were placed before lower atomic weights based on their properties in contradiction to his periodic law.
eg; ⁵⁹Co₂₇ was placed before^58.7Ni₂₈