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ओजोन एक ऑक्सीकारक एवं अपचायक दोनों है। इसे हम निम्नलिखित उदाहरणों द्वारा समझ सकते हैं – 

1. ऑक्सीकारक गुण – ओजोन जल की उपस्थिति में सल्फर को सल्फ्यूरिक अम्ल में ऑक्सीकृत कर देती है। 

S + H₂O + 3O₃ → H₂SO₄ + 3O₂ 

2. अपचायक गुण – ओजोन बेरियम परॉक्साइड को बेरियम मोनोऑक्साइड में अपचयित कर देती है। 

 BaO₂ + O₃ → BaO + 2O₂ ↑

C) atomic number increases and atomic radius decreases

Correct option is  B) F

Correct option is  B) F > O > Cl

(a) It is due to more inter electronic repulsion in fluorine atom due to smaller atomic size than chlorine. 

(b) It is because they have stable electronic configuration, i.e., their octet is complete except He. 

(c) First ionization energy of Mg is more than that of Na because it has smaller atomic size but 2^nd ionization of Mg is less because after losing one electron sodium acquires nearest noble gas configuration.

Correct option is  B) Pauling

The two elements are phosporous and chlorine.

B(5) 1s² 2s² 2p¹ C(6) 1s² 2s² 2p²; B after losing one electron, has completely filled s-orbital from which removal of second electron is more difficult than carbon. 

(b) Be has higher first ionization energy due to completely filled valence s-orbital.

Period : 

When we move from left to right in period, the electronegativity increases due to decrease in atomic size. 

Group: 

When we move from top to bottom in a group, the electronegativity decreases due to increase in atomic size.

It would be Silicon because its electronic configuration is 2, 8, 4. So, it lies in third period and its valency is 4.

Its electronic configuration is 2, 8, 6. 

i) So it belongs to 3rd period (orbit number). 

ii) The number of valence electrons is 6.

Correct option is  B) 8

As we move from top to bottom in a group, atomic size increases and atomic number also increases. So the correct increasing order is Z, Y, X.

1. The element X belongs to group 2. So, the number of valence electrons are 2 and its valency is 2. 

2. The element Y belongs to group 17 or VII. So, the number of valence electrons are 7 and its valency = 8 – 7= 1. 

3. During formation compound elements exchange their valencies. 

∴ The formula of compound is XY₂.

a) A and B belong to same period because the valence electrons of both the elements lie in the same orbit.

b) Elements A and C and elements B and D. 

c) B and D are noble gas elements. 

d) C belongs to 3rd period (orbit number) and III group (Number of valence electrons).

Isolated gaseous atom:- It is free gas phase atom.

Ground State:- The state of an atom when all the electrons in it occupy their lowest energy levels as required by their n and l values is called its ground state.

Correct option is  B) Cl

1) Valency of magnesium is two.

2) Potassium (K) has more electro-positivity.

3) The elements which belongs to 3rd period are Sodium (Na), Magnesium (Mg).

4) Sodium (Na), Potassium (K) belong to 1st Group.

Correct option  (b)   Ionic

The formula of oxide of the element is ZO.

Hydrogen has both +1 as well as -1 oxidation states. So still there is some ambiguity in position of hydrogen.

1) The element belongs to 3rd period and 17th group. So the valence orbit is 3rd and number of valence electrons in that orbit is 7. So its electron configuration is 2, 8, 7. 

2) The number of valence electrons are 7.

3) The valency of element = 8 – 7 = 1. 

4) The atomic number of element is 17. 

5) Name of the element is chlorine. 

6) Chlorine belongs to Halogen family. So Fluorine, Bromine, Iodine, and Astatine have similar properties as chlorine.

As we move from left to right in a period atomic size decreases. So element with seven outermost electrons has least size among all the elements in the same period.

i) Electronic configuration of element is 1s² 2s² 2p⁶ 3s² 3p⁴ or 2, 8, 6.

ii) Period number is 3 because valence electron lies in 3rd orbit. 

iii) Group number is 6 because the number of valence electrons are 6. 

iv) Element belongs to chalcogen family. 

v) Number of valence electrons are 6.

vi) Valency = 8 – 6 = 2. 

vii) It is a non-metal because in a period when we move from left to right nonmetallic character increases.

viii) Name of the element is sulphur.

Properties of elements depend upon number of valence electrons which depend upon electronic configuration. Atomic number is needed to write electronic configuration of an element. It shows that atomic number is more important to determine chemical properties of elements than atomic mass.

a) The number of valence electrons are 4. 

b) Its valency = 8 – 4 = 4. 

c) The electronic configuration of element is 2, 8, 4. (Because 3rd period means third orbit, group 14 has 4 valence electrons). So, the element with atomic number 14 is Silicon.

The first inert gas which contains d-electrons is krypton. Its atomic number is 36 and its electronic configuration is: 

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶. 

Total number of d-electrons = 10 

Total number of p-electrons = 6 + 6 + 6 = 18. 

Total number of s-electrons = 2 + 2 + 2 + 2 = 8. 

∴Difference in total number of p- and s-electrons = 18 - 8 = 10. 

Thus, the inert gas is krypton.

Correct option is  D) ns² np⁶

Inert gases show zero valency because they do not take part in chemical reactions due to stable configuration.

1. The element is phosporous, 

2. The electronic configuration of element is 1s² 2s² 2p⁶ 3s² 3p³ or 2, 8, 5. 

3. It belongs to 3rd period (orbit number is 3) and V or 15 group (Number of electrons in valence orbit is 5.) 

4. Number of valence electrons are 5. 

5. Its valency is 8 – 5 = 3.

Classification is necessary because it is difficult to remember the properties of all the elements separately. It is easy to identify the properties of elements by making them groups with similar properties.

1. Electronic configuration of the given element is 1s² 2s² 2p⁶ 3s² 3p⁵. 

2. So, it is in 3rd period and 17th group of periodic table. 

3. Due to the valency electronic configuration of 3s² 3p⁵ it belongs to 3rd period and 17th group.

Firstly the stimulus is received with the help of dendrites, after that they are transmitted to cyton, and then they travel through the axon and at the end reaches to the terminal branches from where they are transmitted to another neuron.

1. The element with atomic number 11 is sodium and its electronic configuration is 1s² 2s² 2p⁶ 3s¹ or 2, 8, 1. 

2. So it has one valence electron, i.e. present in I group. We know that the elements present in same group have same valence electrons. So they show similar properties.

3. Therefore the other two elements are Lithium and Potassium.

Same, because isotopes of an element differ in the number of neutrons only in their nuclei.

I appreciate the special nature of inert gases because it helps us in explaining the formation of chemical bonds among the atoms of elements and their stability.

Synapse is the junction between two adjustment neuron or nerve cells, i.e. between axon ending of one and the dendrite of the next. Transmission of Nerve Impulse. The information acquired at the end of the dendritic tip of a neuron sets off a chemical reaction which creates an electrical impulse. This impulse travels from the dendrite to the cyton along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals, which cross the synapse and start a similar electrical impulse in a dendrite of the next neuron. In this way nerve impulses travel in the body. Synapse helps in transmitting impulses from one neuron to another.

Whenever any part of the pea tendril comes in contact with the support they start growing slowly whereas part away from it grows rapidly.

Therefore option (c) is correct.

Neural tissue is derived from embryonic ectoderm. It consists of two types of cells.

1. Neurons or nerve fibres : These are structural and functional units of nervous tissue. They conduct nerve impulses and coordinate various body activities. 

2. Neuroglial cells : These are supportive cells which protect neurons throughout CNS and PNS. They perform other functions like secretion of myelin sheath, phagocytosis, production of CSF, etc. e.g Schwann cells, astrocytes, satellite cells, etc.

1. Atomic weight = Equivalent weight x Valency 

2. By using the formula, the atomic weight of Beryllium was calculated as 13.5 (Equivalent weight of Be = 4.5, valency = 3)

3. With this atomic weight the element should be placed in wrong group. 

4. So Mendeleeff predicted its valency is only 2. From that he calculated the atomic weight of Beryllium as 9. 

5. Now it fitted into correct group. 

6. Similarly, Mendeleeff corrected atomic weights of Indium and Gold.

Mendeleeff predicted that some elements were missing in the table so he left blank spaces at the appropriate places in the table.

1. The Electronic configuration of element with atomic number 35 is 2, 8, 18, 7. 

2. So it has seven valence electrons. That’s why it is present in 17th group or VII A group and 4th period. 

3. The element is Bromine.

D) all of these

Given statement is false because at the axonal end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the dendritic end of another neuron.

The brain is situated in the cavity of a bony box called a skull. The brain is contained in a fluid-filled balloon which provides further shock absorption.

Shape of guard cells changes due to change in the amount of water in cells. Whenever there is excess of water cell becomes turgid and guard cells get opened for transpiration to take place. Also, when water is not in excess amount guard cells remains closed.

Therefore, shape of guard cells is determined by amount of water in cells.

The answer is (c) amount of water in cells

Excess of water will turn guard cells turgid and loss of water turn guard cells flaccid.

No, Newlands’ law of octaves was restricted to only 56 elements and did not leave any room for new elements. Elements that were discovered later could not be filled into Newlands’ table in accordance with properties.

1. All the known elements at the time of Dobereiner could not be arranged in the form of triads. 

2. Newlands’ periodic table was restricted only for 56 elements. 

3. As Mendeleeffs classification is based on atomic weight, his classification led to two defects like anomalous pair of elements and dissimilar elements placed together. 

4. Modern periodic table was prepared on the basis of atomic number. So the periods and groups are clearly defined.

5. Hence Dobereiner, Newlands, and Mendeleeffs classifications were not 100% successful, but modern classification is successful.