TEST YOURSELF 2.4 Chemistry 9th Chapter 2

TEST YOURSELF 2.4

1. Why do the isotopes of an element have different atomic masses?

muhammadumar403

Fiverr

Seller

Meet your all needs here! With Me! Hello, My name is Muhammad Umar. I belong to Pakistan. I hope that it will be beneficial for you to make me the head of your project. I have been doing freelancing since 2017 on different sites. Now, I tried my hand on fiverr

https://partners.inspedium.com/135627-5-1-45.html Ans. The isotopes of an element have different atomic masses because they have different number of neutrons their nucleus.

2. How many neutrons are present in C-12 and C-13?

Ans. C 12 has 6 neutrons and C-13 has 7 neutrons. Number of neutrons in an atom is found by the formula:

Number of neutrons, n = A-Z

• For C-12, n = 126 = 6

• For C-13, n = 13- 6 - 7

3. Which of the isotopes of hydrogen contains greater number of neutrons ?

Ans. There are three isotopes of hydrogen, protium, (TH), deuterium (H) and tritium (H). Tritium has greater number of neutrons (3) in its nucleus.

4. Give one example each of the use of radioactive isotope in medicine and radiotherapy ?

Ans. Isotopes of lodine-131 are used for diagnosis of goiter in thyroid gland. For cancer, affecting within the body, Co-60 is used because it emits strongly penetrating gamma rays.

5. How is the goiter in thyroid gland detected?

Ans. The radioactive isotopes are used as tracers in medicine to diagnose the presence of tumor in the human body. Iodine-131 is used for diagnosis of goiter in thyroid gland.

6. Define nuclear fission reaction?

Ans. A nuclear reaction in which a heavy nucleus splits into smaller parts spontaneously or on impact with another particle. During this process large amount of energy is released

7. When U-235 breaks up, it produces a large amount of energy. How is this energy used ?

Ans. When U-235 breaks up a large amount of energy is released which is used to convert water into steam in boilers. The steam then drives the turbines to generate electricity.

8. How many neutrons are produced in the fission reaction of U-235?

Ans. Three neutrons are produced in the fission reaction of U-235.

9. U-235 fission produces two atoms of which elements?

Ans. The uranium nucleus breaks up to produce Barium-139 and Krypton-94.

TEST YOURSELF 2.3 Chemistry 9th Chapter 2

Test yourself 2.3

(1) How many the maximum number of electrons that can be accommodated in a p subshell?

 Ans. Maximum number of electrons that can be accommodated in a p-subshell is six (6).

(2) How many subshells are there in second shell?

Ans. second shell has two subshells i.e. s and p .

(3) Why does an electron first fill 2p orbital and then 3s orbital?

Ans. Electrons are accommodated in different shells according to increasing energy.

An electron first fill 2p orbital and then 3s orbital because 2p orbital is lower in energy than 3s orbital

(4) If both K and L shells of an atom are completely filled; how many total number of electrons are present in them?

Ans. If both K and L shells of an atom are completely filled then there are 10 total electrons present in them.

(5) How many electrons can be accommodated in M shell?

Ans. 2n formula tells us that M shell can accommodate 18 electrons in it.

(6) What is the electronic configuration of a hydrogen atom?

Ans. The electronic configuration of a hydrogen atom is 1s¹.

(7) What is atomic number of phosphorus? Write down its electronic configuration?

Ans. Atomic number of phosphorus is 15. Its electronic configuration is 1s²,2s²,2p⁶,3s²,3p³ .

(8) If an element has atomic number 13 and atomic mass 27; how many electrons are there in each atom of the element?

 Ans. The number of electrons present is this atom is also 13.

(9) How many electrons will be in M shell of an atom having atomic number 15.

Ans. Electronic configuration of an element having atomic number 15 is:

• K shell = 2, L shell = 8, M shell = 5

             There are 5 electrons in M shell.

(10) What is maximum capacity of a shell?

Ans. Maximum capacity of a shell is found by 2n² formula .

TEST YOURSELF 2.2 Chemistry 9th Chapter 2

TEST YOURSELF 2.2

 (1) How was it proved that the whole mass of an atom is located at its centre?

Ans . Since most of the alpha particles in Rutherford's experiment passed through the foil undeflected, therefore most of the volume occupied by an atom is empty. The complete rebounce of a few particles show that the nucleus is very dense and hard.

These observations show that the whole mass of an atom is located at its centre.

 (2) How was it shown that atomic nuclei are positively charged?

Ans . Rutherford bombarded alpha particles on gold foil. These are actually helium nuclei (Ho). The deflection of a few alpha particles proved that there is a 'center of positive

charges in an atom, which is called nucleus of an atom.

(3) Name the particles which determine the mass of an atom?

Ans . The mass of an atom is due to the particles present in the nucleus of an atom. These particles are protons and neutrons.

(4) What is the classical theory of radiation? How does it differ from quantum theory?

Ans . According to Classical Theory of radiation, moving charged particles i.e. electron in an atom release or emit energy continuously. According to Quantum Theory of Max Planck revolving electron in an atom does not absorb or emit energy continuously. The energy of a revolving electron is quantized as it revolves only in orbits of fixed energy.

(5) How can you prove that angular momentum is quantized?

Ans .Let angular momentum (mvr) of 1st orbit is mvr = nh/2TT

By putting the values of h and TT

mvr = 6.63 x 10^-34/2x3.14 = 1.0x 10^-34 kg m²s^-2

TEST YOURSELF 2.1 Chemistry 9th Chapter 2

TEST YOURSELF 2.1

(1) Do you know any element having no neutrons in its atom?

Hydrogen atom has no neutron but in its isotopes like deuterium and tritium, it has one and two neutrons respectively.

(2) Who discovered an electron, a proton and a neutron?

J.J Thomson discovered an electron.

Goldstein discovered a proton.

Chadwick discovered a neutron.

(3) How does electron differ from a neutron?

Sr.No	Electron	Neutron
1	Electron has negative charge.	Neutron has no charge.
2	Electron is light in weight as compared to neutron.	Neutron is Heavier in weight as compared to electron.
3	Electron is present outside the nucleus.	Neutron is present inside the nucleus.
4	Electron is deflected towards positive plate in an electric field.	Neutron does not deflect in electric field.

(4) Explain how anode rays are formed from the gas present in the discharge tube?

Anode rays are produced when electrons or cathode rays collide with the residual gas molecules present in discharge tube and ionize them as follows:

M + e^-    =        M⁺ +2e^-

Where M is any gas.

Chapter # 2 Structure of atoms Exercise short Questions.

Chapter 2

                   Structure of atoms

Exercise Short Questions.

(1) What is the nature of charge on cathode rays?

The nature of charge on cathode rays is negative.

(2) Give five characteristics of cathode rays.

Characteristics of cathode rays.

(a)    They raise the temperature of the object on which they fall.

(b)           They are deflected towards positive plate showing that they       are negatively charged particles.

(c)      When they strike the wall of the glass tube ,they produce light.

(3) The atomic symbol of a phosphorus ion is

            ³¹P^3-

            ¹⁵

(a)How many protons, electrons and neutrons are there in the ion?

    Number of protons   = 15

    Number of electrons   =15+3=18

    Number of neutrons   =31-15  =16 neutrons

(b)What is name of the ion?

    As P has received three electrons and becomes anion also known as phosphide ion.

(c)Draw the electronic configuration of the ion?

     1s²,2s²,2p⁶,3s²,3p⁶.

(d)Name the noble gas which has the same electronic configuration as the phosphorus ion has.

Argon has the same electronic configuration as the phosphorus ion has.

(4) Differentiate between shell and subshell with example of each.

Sr. No	Shell	Subshell
1	Shell is the main or principal energy level.	Each shell is divided into sub energy levels which are known as subshells.
2	Example : K-shell, L-shell, M-shell, etc.	Example : s-subshell, d-subshell,f-subshell, etc.

(5) An element has an atomic number 17. How many electrons are                  present in K, L and M shell of the atom?

Atomic number = 17

Electron = 17

Electrons in K shell = 2

Electrons in L shell = 8

Electrons in M shell = 7

Electronic configuration in subshells :

                                                             1s², 2s² ,2p⁶, 3s², 3p⁵.

(6) Write down the electronic configuration of Al³⁺ . How many electrons are present in its outermost shell?

Atomic number = 13

Electrons in Al³⁺ = 13

Electrons in K shell = 2

Electrons in L shell = 8

8 electrons are present in the outermost shell of Al³⁺.

Electronic configuration in subshell :

                                                                 1s², 2s², 2p⁶

(7) Magnesium has electronic configuration 2, 8 ,2.

(a) How many electrons are in the outermost shell ?

1s², 2s²,2p⁶, 3s²

Electrons in the outermost shell = 2

(b) In which subshell of the outermost shell electrons are present?

       The outermost electrons are present in 3s subshell.

(c) Why magnesium tends to lose electrons?

   All elements wanted to have the electronic configuration of noble gases .So, they can complete their valence shell.

That’s why magnesium lose 2 electrons and become a noble gas like neon (Ne).

(8) What will be nature of charge on an atom when it loses an electron or when it gains an electron?

     When an atom loses an electron, it will be called as cation and its charge becomes positive. And when an atom gains electron, its carge becomes negative and it will be called as anion.

   (9) For what purpose U-235 is used?

         U-235 is used to get a large amount of energy by controlled  nuclear fission process in nuclear reactors. This energy is used in boilers to convert water into steam. The steam is used to generate electricity.

(10) A patient has goiter. How will it be treated ?

         Iodine-131 is used to detect the goiter in thyroid gland.

(11) Give three properties of positive rays.

                             I.            They travel in a straight line opposite to the direction of cathode rays.

                          II.            The nature of these rays depends upon the nature of gas present in discharge tube.

                       III.            They show deflection in electric and magnetic field that shows they are positively charged particle.

(12) What are the defects of Rutherford’s atomic model?

·       According to the classical theory of radiation, electrons being charged particles should emit energy continuously and ultimately fall down into the nucleus.

·       If the electrons emit energy continuously, they should form a continuous spectrum, but in fact line spectrum was observed.

(13) As long as electron remains in an orbit, it does not emit or absorb energy. When does it emit or absorb energy?

       Electron emit energy when it jumps from higher to lower orbit and absorb energy when it jumps from lower to higher orbit.

Chapter 1 Introduction to Biology Short Questions.

Chapter 1

                   Introduction to Biology

Short questions.

(1) Define macromolecules.

Molecules having high molecular weight are called macromolecules.

Example:

              Proteins, carbohydrates etc.

(2) Define Biotechnology.

The branch which deals with the practical application of living organism to make substances for the welfare of mankind is called biotechnology.

(3) Define Organ system.

It is defined as “The different organs performing related functions are organized together in the form of organ system. In this system ,every organ carries out its specific function and all organs   appear as the function of that organ system.

(4) Write the scientific contributions of Bu Ali Sina?

(a)   His book “Al qanun-fi al tib is known as the canon of  medicine in West.

(b)           He is honored as the founder of medicine and called as Avi Cenna in the West.

(5) Name some unicellular organisms.

Amoeba, Bacteria, Euglena and Paramecium are some unicellular organisms.

(6) Differentiate between cell biology and histology.

Cell Biology	Histology
This branch deals with the study of cells.	Histology is the branch which deals with the microscopic study of tissues.

Remember:

                        Always write the difference between two things by putting a line between them.

(7) Define colonial organization.

In this organization, many unicellular organisms live together but do not have any division of labor among them. Every organism in a colony live its own life and does not depend on other cells.

Example:

                 Volvox is a green alga that shows colonial organization.

(8) Define parasites.

The organism which takes food and shelter from living hosts and in return harm them.

Example:

              Mosquitoes, etc

(9) What are vegetative organs of a plant?

The parts of plant body that take part in sexual reproduction are called vegetative organs.

Example:

                Stem, roots and leaves, etc

(10)                  Define biogeography.

           Biogeography includes the occurrence and distribution of different species of living organisms in different geographical region of the world. It also applies the knowledge of the characteristics of particular geographical regions to determine the characteristics of living organisms found there.

(11)                  Write the main divisions of biology.

           Biology has three main divisions :

(a)  Zoology

(b) Botany

(c)  Micro biology

(12)                  Define Bio elements.

            The elements which are the constituents of living organisms are called bio elements.

Example,

                 Carbon ,hydrogen etc.

(13)                  What do you mean by entomology.

           Entomolgy is the branch of biology which deals with the study of insects.

(14)                  What is the scientific name of frog.

         The scientific name of mustard plant is “Brassica campestris”                                                                                                                   

          Remember :

                                Scientific name of every specie is underlined when it is written with hand.

(15)                  Define Tissue level.

           In multi cellular organisms, when similar cells are organized into groups ,they are called tissues. Each cell in a tissue carries on its own life processes but it also carries on some special processes related to the function of the tissue.

(16)                  Define fossils?

           The remainder of old plants and animals are called fossil fules.

(17)Define immunology?

         The branch of biology which deals with the study of immune system of the animals which defend the body against invading microbes.

(18)Define biosphere level?

     Biosphere level can be defined as the part of earth inhabited by organisms communities .It constitute all ecosystems and is called the one of life on earth.

(19)write two applications of horticulture in daily life?

              Horticulture deal with the betterment of existing varities of plants.It deals with the more yield production of fruits and crop plants.

(20)Name six important bioelements?

       The six important bioelements are O,C,H,N,Ca, and P.