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i) Atomic number is the total number of protons present in the nucleus of an atom. It is also equal to the number of electrons for a neutral atom. Example, atomic number of sodium is 11. ii) Mass number is the number of protons and neutrons in the nucleus taken together. For example, mass number of sodium is 23 g/mol. iii) Isotopes are elements with the same atomic number but different mass numbers. Example, hydrogen has 3 isotopes - protium (1H1), deuterium (2H1) and tritium (3H1). iv) Isobars are elements which have different atomic numbers but the same mass number. They are different chemical elements. Example, iron and nickel, both have mass number 58, whereas atomic numbers are different.

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Yogita Ingle 5 years, 1 month ago

i) Atomic number is the total number of protons present in the nucleus of an atom. It is also equal to the number of electrons for a neutral atom. Example, atomic number of sodium is 11.

ii) Mass number is the number of protons and neutrons in the nucleus taken together. For example, mass number of sodium is 23 g/mol.

iii) Isotopes are elements with the same atomic number but different mass numbers. Example, hydrogen has 3 isotopes - protium (¹H₁), deuterium (²H₁) and tritium (³H₁).

iv) Isobars are elements which have different atomic numbers but the same mass number. They are different chemical elements. Example, iron and nickel, both have mass number 58, whereas atomic numbers are different.

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Compare all the proposed models of an atom give in this chapter.

Posted by Naina Singh Rajput 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Ankit Ambasta 7 years, 2 months ago

JJ Thomson's model -An atom consists of positive sphere and electrons are embaded in it. -An atom as whole is neutral. Rutherford's model -An atom consists of a positively charged sphere known as neucleous.Nearly all mass of atom is confide in neucleous. -Electrons revolve around the neucleous. Bhor's model -Only certain special orbits known as discrete orbits are allowed inside the atom. -Electrons do not radiate energy while revolving around the neucleous.

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Describe Bhor's model of the atom ?

Posted by Naina Singh Rajput 7 years, 2 months ago

CBSE > Class 09 > Science

2 answers

Nandini Sharma❤️ 7 years, 2 months ago

According to Bhor's model of an atom, 1. Some orbits known as discrete orbits are allowed in the atom. 2. While revolving in these orbits electrons do not gain or radiate energy. 3. These orbits are known as energy levels. 4. They are denoted by alphabets K,L,M,N. 5. Number of electrons in each shell can be found out by the formula 2n^2.

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Yogita Ingle 7 years, 2 months ago

Neils Bohr, a Danish physicist, in 1913 proposed model of atom which rectified the problems left by Rutherford’s Model. He proposed that

Electrons revolve round the nucleus in a fixed orbit.
He called these orbits as ‘stationary orbit’.
Each stationary orbit is associated with fixed amount of energy, thus electrons do not radiate energy as long as they keep on revolving around the nucleus in fixed orbit.

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What are the limitations of Rutherford 's model of the atom?

Posted by Naina Singh Rajput 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 2 months ago

Rutherford’s model was unable to explain the stability of an atom. According to Rutherford’s postulate, electrons revolve at a very high speed around a nucleus of an atom in a fixed orbit. However, Maxwell explained accelerated charged particles release electromagnetic radiations. Therefore, electrons revolving around the nucleus will release electromagnetic radiation.
The electromagnetic radiation will have energy from the electronic motion as a result of which the orbits will gradually shrink. Finally, the orbits will shrink and collapse in the nucleus of an atom. According to the calculations, if Maxwell’s explanation is followed Rutherford’s model will collapse with 10-8 seconds. Therefore, Rutherford atomic model was not following Maxwell’s theory and it was unable to explain an atom’s stability.
Rutherford’s theory was incomplete because it did not mention anything about the arrangement of electrons in the orbit. This was one of the major drawbacks of Rutherford atomic model.

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What are the limitation of J.J Thomson's model of the atom?

Posted by Naina Singh Rajput 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 2 months ago

According to J.J. Thomson’s model of an atom, an atom consists of a positively charged sphere with electrons embedded in it. However, it was later found that the positively charged particles reside at the centre of the atom called the nucleus, and the electrons revolve around the nucleus.

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Difference between symptoms and sign.

Posted by Ashlok Kumar 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Avishek Vishwakarma 7 years, 2 months ago

Symptoms is a change in normal functioning of the body which is felt by a patient,but which cannot be on our observed by doctor while sign of a disease is a change in the bodily function or structure that can be observed.

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How many electrons are in the L shell

Posted by Logesh Selva 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Jaimina Gharia 7 years, 2 months ago

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Write short note on Porifera

Posted by Subrat Nayak 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Gaurav Seth 7 years, 2 months ago

They are primitive animals.
They are generally multicellular organisms with specialised cells but these cells do not group together to form tissues.
Most of them are marine, i.e., found in the seas. Some of them are also found in ponds and rivers.
They possess pores all over the body.
Reproduction can be by both sexual and asexual methods.
Sensory system is absent.
Mouth and **** are absent.
A distinct canal system with inlets and outlets for water circulation inside the body is present. They obtain food and oxygen by means of water. The collar cells filter out food particles from the water current flowing through the canal system.
Examples are: Sycon, Spongilla and Euplectella.

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Compare the properties of electrons ,protons and neutrons .

Posted by Naina Singh Rajput 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Gaurav Seth 7 years, 2 months ago

Electron	Proton	Neutron
(i)	Electrons are present outside the nucleus of an atom.	(i)	Protons are present in the nucleus of an atom.	(i)	Neutrons are present in the nucleus of an atom.
(ii)	Electrons are negatively charged.	(ii)	Protons are positively charged.	(ii)	Neutrons are neutral.
(iii)	The mass of an electron is considered to negligible.	(iii)	The mass of a proton is approximately 2000 times as the mass of an electron.	(iii)	The mass of neutron is nearly equal to the mass of a proton.

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What is find the neutron

Posted by Karan Srivastava 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Sayahnika Mishra 7 years, 2 months ago

James Chadwick discovered the neutron(having no charge) in 1932

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What is syphilis

Posted by Asif Khan 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Ankita Nayak 7 years, 2 months ago

A bacterial infection usually spread by sexual contact that starts as a painless sore.

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What is a tissue and what is it's work and what is it's types

Posted by Himanshu Singh Jagawat (Hsj) 7 years, 2 months ago

CBSE > Class 09 > Science

2 answers

Asif Khan 7 years, 2 months ago

The mass of cells that forms the bodies of the humans,animals and plants There are four main types of tisseue (1) epithelial (2) muscle (3)Nervous (4) connecitve

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Nikhil Dhakad 7 years, 2 months ago

Tissue is made up cell

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What is the full forms of the cfc

Posted by Monu Kumar 7 years, 2 months ago

CBSE > Class 09 > Science

3 answers

Ankita Nayak 7 years, 2 months ago

Chloro Fluoro Carbon.. is the r8 one don't be confused!

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Jessika .... 7 years, 2 months ago

Chloro Fluoro Carbon

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Himanshu Singh Jagawat (Hsj) 7 years, 2 months ago

Chloro phloro carbon

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A farmer moves along the boundary of a square field of side 10 m in 40 seconds what will be the magnitude of the displacement of the farmer and end of 2 minute 20 second from his initial position

Posted by Shubhojeet Das 7 years, 2 months ago

CBSE > Class 09 > Science

2 answers

Rahul Dubey 7 years, 2 months ago

Use Pythagoras theorem. Just as follows. Let the ABCD be the square field. Then the displacement will be the diagonal of the field. And after calculation the answer will be 10×2^1/2

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Ashlok Kumar 7 years, 2 months ago

5metres

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Explain how, a karate player can break a pile of tiles with a speed of 5m/s.

Posted by Dheeraj Upraity 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Rahul Dubey 7 years, 2 months ago

By moving his hand with high velocity he acquires high momentum and then he breaks the piles.

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Explain the following giving examples. a) saturated solution b)pure substance c) colloid d)suspension

Posted by Ankita Jaiswal 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Ankita Nayak 7 years, 2 months ago

A) a solution in which no more solute can be dissolved in the solvent. B) A pure substance or chemical substance is a material that has a constant composition (is homogeneous) and has consistent properties throughout the sample. C) A colloid is a heterogeneous mixture whose particles are not as small as solution but they are so small that cannot be seen by naked eye. D) A suspension is a heterogeneous mixture in which solids are dispersed in liquids. The solute particles in suspension do not dissolve but remain suspended throughout the medium.

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Write the information of gmrt?

Posted by Shital Thakur 7 years, 2 months ago

CBSE > Class 09 > Science

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In which water easier to swim sea water or fresh water. Why8?

Posted by Tara Chettri 7 years, 2 months ago

CBSE > Class 09 > Science

3 answers

Ankit Ambasta 7 years, 2 months ago

Sea water because sea water is more denser then fresh water so object will experience more upthrust then in on fresh water and it will be easier to swim.

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Himanshu Singh Jagawat (Hsj) 7 years, 2 months ago

In sea water because sea water contains salt that's why it is heavier than fresh water and it pulls the person who is swimming in the sea water

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Omkara Ghandwani 7 years, 2 months ago

Fresh water Because sea water ? has more amount of particles (salt)

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What is Plasmolisis????

Posted by Jay Prakash Prajapati 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Gaurav Seth 7 years, 2 months ago

When a living plant cell loses water through osmosis, there is a shrinkage or contraction of the protoplasm away from the cell wall. This phenomena is called plasmolysis.

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Nyc

Posted by Dharmenxra Kumar 7 years, 2 months ago

CBSE > Class 09 > Science

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.Mam I say which formula motion chapter

Posted by Koushik Tak 7 years, 2 months ago

CBSE > Class 09 > Science

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Difference between acute desease and chronic desase in short

Posted by Sargam Thakur 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Priyanka Chaudhary 7 years, 2 months ago

Acute disease last for short period of time and chronic disease last for long time. Example of acute is cholera and chronic is cancer. Thank me for answer

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State laws of reflection of sound

Posted by Piyush Choudhary 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Khushbu Kotwani 7 years, 2 months ago

it is same as laws of reflection of light when sound reflects the angle of incidence is equal to angle of reflection and normal ray incident ray and reflected ray lie in the same plane

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Why AIDS only effects immunity system?

Posted by Aditya Sharma 7 years, 2 months ago

CBSE > Class 09 > Science

2 answers

Avishek Vishwakarma 7 years, 2 months ago

Because it attack only the major part of human body which is immune system that can destroy HIV/Aids.

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Rahul Dubey 7 years, 2 months ago

Because Aids is not a disease it is a syndrome.

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Compaire all the proposed models of an atom given in this chapter

Posted by Aditi Verma Annu Verma 5 years, 11 months ago

CBSE > Class 09 > Science

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What is convex mirror

Posted by Lokesh Singh 7 years, 2 months ago

CBSE > Class 09 > Science

1 answers

Shital Thakur 7 years, 2 months ago

Concave mirror:if the inner surface of the spherical mirror is the reflecting surface then it is called concave mirror ✌️convex mirror:if the outer surface of the spherical mirror is the reflecting surface then it is called convex mirror.

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Electro configuration

Posted by Ankesh Singh 7 years, 2 months ago

CBSE > Class 09 > Science