Lakhmir Singh solutions for Chemistry [English] Class 9 chapter 4 - Structure of the Atom [Latest edition]

Which subatomic particle is not present in an ordinary hydrogen atom?

Name the scientists who described the arrangement of electrons in an atom.

What is the maximum number of electrons which can be accommodated in the K shell of an atom?

What is the maximum number of electrons which can be accommodated in the L shell of an atom?

What is the maximum number of electrons an M shell of the atom can accommodate?

What is the maximum number of electrons that can go into the N shell of an atom?

What is the maximum number of electrons which can be accommodated in the :
(a) innermost shell of an atom?
(b) outermost shell of an atom?

Name the three subatomic particles present in an atom.

Name the negatively charged particle present in the atoms of all the elements.

Name the scientist who discovered electron.

What is the usual symbol for (a) and electron (b) a proton, and (c) a neutron?

State whether the following statement is true or false :
Thomson proposed that the nucleus of an atom contains protons and neutrons.

State whether the following statement is true or false :
The cathode rays obtained from all the gases consist of negatively charged particles called electrons.

State whether the following statement is true or false :
The anode rays obtained from all the gases consist of positively charged particles called protons.

Name the central part of an atom where protons and neutrons are held together.

What are the various letters used by Bohr to represent electron shells in an atom?

Name the particles which actually determine the mass of an atom.

Name the positively charged particle present in the atoms of all the elements.

What is the Electronic Configuration of a Hydrogen Atom?

How many times is a proton heavier than an electron?

Name the gas which produces anode rays consisting of protons in the discharge tube experiment.

Which part of an atom was discovered by Rutherford's alpha particle scattering experiment?

What is the positive charge on the nucleus of an atom due to?

State the number of electrons present in the outermost shell of the atoms of the following elements :(i) Neon 
(ii) Chlorine

Which shell of an atom can accommodate a maximum of :
(a) 8 electrons ?
(b) 32 electrons ?

Name the shell of an atom which can accommodate a maximum of :
(a) 2 electrons ?
(b) 18 electrons ?

Which subatomic particle was discovered by : Chadwick ?

Which subatomic particle was discovered by : Thomson?

Which subatomic particle was discovered by : Goldstein ?

Name the subatomic particle whose relative charge is : +1

Name the subatomic particle whose relative charge is : –1

Name the subatomic particle whose relative charge is : 0

Fill in the blank of the following statement :

The anode rays obtained from hydrogen gas consist of particles called ________

Fill in the blanks- The number of protons in the nucleus of an atom is called its ....................

Fill in the blank of the following statement : 

The total number of protons and neutrons in the nucleus of an atom is called its _________.

Fill in the blanks of the following statements :

An atom has atomic mass number 23 and atomic number 11. The atom has_________ electrons.

Cathode rays are a beam of fast moving _________

The maximum number of electrons that can be accommodated in L shell are_________

The maximum number of electrons that can go into the M shell is _________

Fill in the blanks of the following statement :

An atom of an element has 11 protons, 11 electrons and 12 neutrons. The atomic mass of the atom is ___________.

Fill in the blank of the following statement :

 If the nucleus of an atom has atomic number 17, mass number 37 and there are 17 electrons outside the nucleus, the number of neutrons in it is __________.

Fill in the blank of the following statement :

All the mass of an atom is concentrated in a small region of space called the ___________.

Fill in the blank of the following statement :

The subatomic particle not present in a hydrogen atom is ________

Fill in the blank of the following statement :

The electron has _________ charge, the proton has _________ charge, and the neutron has _________ charge.

What is an electron? State its relative mass and charge.

What is the absolute mass and charge of an electron?

Give the evidence for the existence of nucleus in an atom.

What important information is furnished about the nucleus of an atom by the alpha particle scattering experiment of Rutherford?

An element has an atomic number 12. How many electrons will be present in the K, L and M energy shells of its atom?

How was it shown that an atom has a lot of empty space within it?

Why is an atom neutral inspite of the presence of charged particles in it?

(a) Which of the nuclear particles is present in the same fixed number in the atoms of any particular element?

(b) What do we call this number which is characteristic of a particular element?

What is a proton? State its relative mass and charge.

What is the absolute mass and charge of a proton?

How does a proton differ from an electron?

State two observations which show that atom is not indivisible.

All the gases from cathode rays and anode rays when electricity is passed through them :What does the formation of cathode rays tell us about the atoms?

All the gases from cathode rays  anode rays when electricity is passed through them :

What does the formation of anode rays tell us about the atoms?

What do you understand by the term "electronic configuration" of an element? Write down the electronic configuration of oxygen (At. No. = 8).

An element has an atomic number 12. How many electrons will be present in the K, L and M energy shells of its atom?

(a) What is the nucleus of an atom and what is the nature of charge on it?

(b) Name the scientist who discovered the nucleus of atom.

Name the particles used by Rutherford in his experiment on the discovery of nucleus. Also state the charge on these particles.

An element has atomic number 13 and an atomic mass of 27.
(a) How many electrons are there in each atom of the element ?
(b) How are these electrons distributed in the various energy levels ?

Write the distribution of electrons in an atom of element whose atomic number is 18. What is special about the outermost electron shell (or valence shell) of the atom of this element?

What is a neutron? State its relative mass and charge.

Compare an electron, a proton and a neutron in respect of their relative masses and charges.

What is a proton? How does it differ from a neutron?

Compare an electron and a proton in respect of mass and charge.

Compare a proton and a neutron in respect of mass and charge.

How does an electron differ from a neutron?

State the location of electrons, protons and neutrons in an atom.

Fill in the following blanks :

Fill in the following blanks in respect of an atom of an element 

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

(b) Explain how, cathode rays are formed from the gas taken in the discharge tube.

(c) What conclusion is obtained from the fact that all the gases from cathode rays?

(a) Describe Thomson's model of the atom. Which subatomic particle was not present in Thomson's model of the atom?

 The mass number of an element is 18. It contains 7 electrons. What is the number of protons and neutrons in it? What is the atomic number of the element?

Describe the Rutherford's model of an atom. State one drawback of Rutherford's model of the atom.

The mass number of an element is 23 and it contains 11 electrons. What is the number of protons and neutrons in it? What is the atomic number of the element?

Describe Bohr's model of the atom. How did Neils Bohr explain the stability of atom?

An element has an atomic number of 11 and its mass number is 23. What is the arrangement of electrons in the shells? State nuclear composition of an atom of the element.

(a) What is meant by (i) atomic number, and (ii) mass number, of an element? Explain with the help of an example.

(b) What is the relation between the atomic number and mass number of an element?

(c) If an element M has mass number 24 and atomic number 12, how many neutrons does its atom contain?

Rutherford's alpha particle scattering experiment led to the discovery of :

Which of the following is the correct electronic configuration of sodium?

The particle not present in an ordinary hydrogen atom is :

The subatomic particle called electron was discovered by :

Which of the following represents the correct electron distribution in magnesium ion?

The correct electronic configuration of a chloride ion is :

Goldstein's experiments which involved passing high voltage electricity through gases at very low pressure resulted in the discovery of :

The number of electrons in the atom of an element X is 15 and the number of neutrons is 16. Which of the following is the correct representation of an atom of this element ?

The ion of an element has 3 positive charges. The mass number of atom of this element is 27 and the number of neutrons is 14. What is the number of electrons in the ion?

The first model of an atom was given by :

Which of the following statement is always correct?

From the symbol `""_15^31"P"`, state :
(i) mass number of phosphorus,
(ii) atomic number of phosphorus, and
(iii) electron configuration of phosphorus.

The atom of an element X has 7 electrons in its M shell.
(a) Write the electronic configuration of element X.
(b) What is the atomic number of element X?
(c) Is it a metal or a non-metal?
(d) What type of ion will be formed by an atom of element X? Write the symbol of the ion formed.
(e) What could element X be?

An atom of element E contains 3 protons, 3 electrons and 4 neutrons :
(a) What is its atomic number?
(b) What is its mass number?
(c) Write the electronic configuration of the element E.
(d) State whether element E is a metal or non-metal. Why?
(e) What type of ion, cation or anion, will be formed by an atom of element E? Why
(f) Write the symbol of the ion formed by an atom of element E.
(g) What could element X be?

An atom of an element X may be written as `""_9^4"X"`
(a) What does the figure 9 indicate?
(b) What does the figure 4 indicate?
(c) What is the number of protons in atom X?
(d) What is the number of neutrons in atom X?
(e) What is the number of electrons in atom X?
(f) How many electrons are there in the outermost shell of an atom of element X?
(g) Write the symbol of ion formed by an atom of element X.

The electronic configuration of an element Z is 2, 8, 8.
(a) What is the atomic number of the element?
(b) State whether element Z is a metal or a non-metal.
(c) What type of ion (if any) will be formed by an atom of element Z? Why?
(d) What is special about the outermost electron shell of the atom of this element?
(e) Give the name and symbol of element Z.
(f) Name the group of elements to which Z belongs.

The total number of electrons in a nitrogen atom is 7. Find the number of valence electrons in it.

What is the general name of the elements having 8 electrons in the valence shell of their atoms?

Which noble gas has less than 8 electrons in the valence shell of its atom? What is this number?

State one use of radioactive isotopes in medicine.

Give one example of a radioactive isotope which is used as a fuel in the reactors of nuclear power plants.

Name the Radioactive Isotope Which is Used in the Treatment of Cancer.

Which radioactive isotope is used to determine the activity of thyroid gland?

State one use of radioactive isotopes in industry.

State whether the following statement is true or false :
Radioactive isotope of iodine is used for making the medicine called tincture iodine.

What name is given to those atoms which contain the same number of protons and electrons but different number of neutrons?

What is the relationship between an atom containing 11 protons, 11 electrons and 11 neutrons, and another atom containing 11 protons, 11 electrons and 12 neutrons?

What name is given to the pair of atoms such as `""_7^14"N"` and `""_7^15"N"` ?

What name is given to those isotopes which have unstable nuclei and emit various types of radiations ?

Fill in the following blanks in respect of an atom of an element :

Complete the Following Statements :
Magnesium has 2 valence electrons in the ............. shell.

The valency of nitrogen in N₂ molecule is .............

Complete the following statements :
Isotopes have different mass numbers because their nuclei contain different number of ............

Some boron atoms have mass number 10 and some have mass number 11. These boron atoms with different mass numbers are called .............

The nucleus of an atom has 5 protons and 6 neutrons. What would be the (a) atomic number, (b) mass number, (c) the number of electrons, and (d) the number of valence electrons, per atom of this element?

Write the electronic configuration of the element with atomic number 17. Indicate the valency of the element.

The atomic number of an element X is 16.
(a) Write down the electronic configuration of X.
(b) What will be the valency of X ?

What valencies will be shown by the elements A, B, C, D and E having atomic number 2, 4, 8, 10 and 13 respectively.

Give one use each of the following radioactive isotopes :
(a) Uranium-235
(b) Cobalt-60

Explain why `""_1^3"H"` and `""_2^3"H"` are not considered isotopes.

What is the reason for the different atomic masses of the isotopes of an element ?

What is the reason for the identical chemical properties of all the isotopes of an element ? Explain with the help of an example.

What is the reason for the slightly different physical properties of all the isotopes of an element ?

Explain why, the atomic masses of many elements are in fractions and not whole numbers.

Which of the following are isotopes and which are isobars ?
Argon, Deuterium, Calcium, Tritium, Protium

Hydrogen has three isotopes written as : 
`""_1^1"H"`  `""_1^2"H"` `""_1^3"H"`

Explain why :
(i) these isotopes have almost identical chemical properties.
(ii) they are electrically neutral.

Given that the percentage abundance of the isotope `""_10^20"Ne"` is 90% and that of the isotope `""_10^22"Ne"` is 10%, calculate the average atomic mass of neon.

What are isobars ? Explain with an example.

For the symbols H, D and T, write the subatomic particles (protons, neutrons and electrons) found in each one of them.

An element has Z = 7. What is the valency of the element ? Also name the element.

(a) What are valence electrons? Where are valence electrons situated in an atom ?
(b) What is the number of valence electrons in the atoms of an element having atomic number 13 ? Name the valence shell of this atom.

(a) What are isotopes ? Explain by giving an example.

(b) Give one similarity and one difference between a pair of isotopes.

(c) Give the number of protons, neutrons and electrons per atom in the two isotopes of chlorine `""_17^35"Cl"` and `""_17^35"Cl"`.

(a) What are radioactive isotopes ? Give two examples of radioactive isotopes.

(b) Give any two uses of radioactive isotopes.

(c) An element Z contains two naturally occurring isotopes `""_17^35"Z"` and `""_17^37"Z"`. If the average atomic mass of this element be 35.5 u, calculate the percentage of two isotopes.

(a) Define valency of an element. What valency will be shown by an element having atomic number 14 ?
(b) What is the relation between the valency of an element and the number of valence electrons in its atoms ? Explain with examples.

The mass number of two atoms X and Y is the same (40 each) but their atomic number are different (being 20 and 18 respectively). X and Y are examples of :

Which of the following statement is correct about the atom of an element ?

There are two species represented as ³⁵Cl and ³⁷Cl. Which of the following statement is correct regarding these species ?

The radioactive isotope used in the treatment of cancer is :

Elements having valency 'one' are :

In a sample of ethyl ethanoate (CH₃COOC₂H₅), the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it ?

Which of the following elements does not exhibit electrovalency ?

The number of valence electrons in a graphite atom is :

The atomic number of four elements A, B, C and D are 12, 13, 15 and 3 respectively. The element which cannot form a cation is :

The number of valence electrons in a sulphide ion, S^2–, is :

For an element, Z = 9. The valency of this element will be :

Four elements W, X, Y and Z contain 8, 11, 9 and 17 protons per atom respectively. The element which cannot form an anion is most likely to be :

The four atomic species can be represented as follows. Out of these, the two species which can be termed isobars are :

(i)`""_60^201"X"`

(ii)`""_61^200"X"`

(iii)`""_58^200"X"`

(iv)`""_60^203"X"`

There are four elements P, Q, R and S having atomic numbers of 4, 18, 10 and 16 respectively. The element which can exhibit covalency as well as electrovalency will be :

The atomic number of an element X is 8 and that of element Y is 4. Both these elements can exhibit a valency of :

The isotopes of an element contain :

What is the number of valence electrons in :
(a) sodium ion, Na⁺
(b) oxide ion, O^2–

Atom A has a mass number 209 and atomic number 82.
Atom B has a mass number 209 and atomic number 83.
(i) How many protons atom A has ?
(ii) How many protons atom B has ?
(iii) Are atoms A and B isotopes of the same element ?

Which of the following pairs are isotopes ? Give reasons for your choice :

(i) `""_26^58"A"`,  `""_28^58"B"` or (ii) `""_35^79"X"`,  `""_35^80"Y"` 

Three different atoms of oxygen are represented as : 
`""_8^16"O"`, `""_8^17"O"`, `""_8^16"O"`
(i) What do the subscripts (lower figures) and superscripts (upper figures) represent ?
(ii) What factor is responsible for the change in the superscripts 16, 17 and 18, though the element is the same ?
(iii) What is the usual name for such atoms of an element ?
(iv) Give the nuclear composition of  `""_8^16"O"`.

The atomic species A and B have different number of protons but the same number of nucleons. On the other hand, the atomic species X and Y have the same number of protons but different number of nucleons. Which pair is an example of isobars ? Why ?

Composition of the nuclei of two atomic species A and B is given as under  :

Give the mass numbers of A and B. What is the relation between the two species and which element or elements they represent ?

Which of the following pairs are isobars ?
(i) `""_26^58"A"`, `""_28^58"B"`

(ii) `""_35^79"X"`, `""_35^80"Y"`
Give reasons for your choice.

The number of protons, neutrons and electrons in particles A to E are given below :

Giving reasons, find a pair of isotopes from the above particles.

The composition of two atomic particles is given below :

(i) What is the mass number of X ?

(ii) What is the mass number of Y ?

(iii) What is the relation between X and Y ?

(iv) Which element/elements do they represent ?