9th chemistry chapter 2 solved exercise short questions

Structure of Atom

9th chemistry chapter 2 solved exercise short questions

Q#1 : What is nature of charge on cathode rays ?

Cathode rays have negative charge on them.

Q#2 : Give five characteristics of cathode rays ?

Characteristics of Cathode rays :

  1. Cathode rays travel in a straight line perpendicular to the cathode surface .
  2. They raise the temperature of the body on which they fall.
  3. Light is produced when these rays hit the walls of discharge tube .
  4. They can cast a sharp shadow .
  5. The nature of rays do not depend upon the nature of gas used in discharge tube .

Q#3 : The atomic symbol of a phosphorus ion is given as :

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

Atomic number is 15

  • Number of protons = 15

It has -3 charge which shows gain of 3 electrons.

  • Number of electrons = 15 + 3 = 18
  • Number of neutrons = 31 – 15 = 16

(b) : What is name of the ion ?

P-3 is called phosphide ion .

(c) : Draw the electronic configuration of the ion .

The electronic configuration of P3- :

Electronic configuration in Shells

1s² , 2s² , 2p⁶ , 3s² , 3p⁶

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

Argon (Ar)

Q#4 : Differentiate between shell and subshell with examples of each .

Q#5 : An element has an atomic number 17 . How many electrons are present in K, L and M shells of the atom ?

Atomic number = Z = 17

K = 2 electrons

L = 8 electrons

M = 7 electrons

Q#6 : Write down the electronic configuration of Al+3 . How many electrons are present in its outermost shell ?

Aluminum has 13 electrons ( atomic number = 13 ) while Al+3 ion has 10 electrons due to loss of 3 electrons.

Electronic configuration (Al+3) in shells :

This table shows electronic configuration of Al+3 in shells.

Electronic configuration of Al+3 in sub-shells:

1s² , 2s² , 2p⁶

Q#7 : Magnesium has electronic configuration 2, 8, 2.

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

The outermost shell of Mg has only two electrons.

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

The outermost electrons of “Mg” are present in “s” subshell of the 3rd shell “M” (3s²) because its electronic configuration is :

1s² , 2s² , 2p⁶ , 3s²

(c) : Why magnesium tends to lose electrons ?

Magnesium is an electropositive metal. It can easily lose its two outermost electrons and get charge (2+).

Q#8 : What will be the nature of charge on an atom when it loses an electron or when it gains an electron ?

  • When an atom loses its electron, it becomes positively charged called Cation .
  • When an atom gains electrons, it becomes negatively charged ion called Anion .

Q#9 : For what purpose is U-235 used ?

Use of U-235 :

U-235 is used to get large amount of energy which can be used to drive the turbines to generate electricity .

Q#10 : A patient has goiter . How will it be detected ?

Detection of Goiter :

I-131 is given to the patient . The amount of iodine absorbed and the radiations emitted from thyroid glands is measured to detect tumor .

Q#11: Give three properties of positive rays .

Properties of Positive Rays :

Positive rays are also called “canal rays ” .

  1. These rays travel in a straight line in a direction opposite to the cathode rays .
  2. These are positively charged rays .
  3. The nature of these rays depend upon the nature of gas filled in discharge tube .

Q#12 : What are the defects of Rutherford’s atomic model ?

Defects of Rutherford’s Atomic Model :

  • According to this atomic model , a revolving electron being a charged particle must radiate energy continuously .By losing energy , it will ultimately fall in the nucleus which is impossible .
  • Rutherford’s model of atom also suggests that there would be a continuous atomic spectrum but continuous atomic spectrum is obtained .

Q#13 : As long as electrons remains in an orbit , it does not emit or absorb energy. When does it emit or absorb energy ?

  • Electrons emits energy (ΔE=E2-E1) when it jumps from higher energy level to lower energy level .
  • Electron absorbs energy (ΔE=E2-E1) when it jumps from lower energy level to higher energy level .
9th Chemistry , Chapter 2 , Structure of Atom , solved exercise short questions , free notes
9th Chemistry , Chapter 2 , Structure of Atom , solved exercise MCQs .

9th chemistry chapter 2 solved exercise short questions

Leave a Comment

Your email address will not be published. Required fields are marked *