Atomic structure refers to the structure of an atom, which consists of a nucleus (centre) containing protons (positively charged) and neutrons (neutral). Electrons, which are negatively charged particles, revolve around the nucleus. The study of an atom’s structure provides a great deal of insight into the entire class of chemical reactions, bonds, and their physical properties. In the 1800s, John Dalton proposed the first scientific theory of atomic structure.
Download Class 9 Chemistry Worksheet on Chapter 4 Structure of the Atom Set 2 PDF
CBSE Class 9 Chemistry Worksheet Chapter 4 Structure of the Atom– Set 2
Q-1:Boron occurs naturally as two isotopes with atomic masses of 10.01 and 11.01. Boron has an atomic mass of 10.81. Determine the percentage of each isotope in natural Boron.
Q-2: Which of the following statements about a proton is incorrect?
a) It is a positively charged particle
b) The mass of proton is equal to the mass of neutron
c) It resides in the nucleus of an atom
d) It is a constituent of cathode rays
Q-3: Isobars are two atoms that have
a) the same mass number but different atomic numbers
b) the same number of protons but different electrons.
c) the same number of protons and electrons.
d) the same atomic number but different mass number
Q-4: An atom with the atomic mass number 39 contains 20 neutrons. What is the atom’s atomic number?
Q-5: Give the electronic configurations of the following ions:
i) H–
ii) S2-
iii) N-1
iv) N2+
Q-6: An element’s atomic mass is equal to twice its atomic number. If the L-shell contains six electrons, then
a) Predict its valency
b) Find the name of the element.
Q-7: How many nucleons are present in an atom of Americium, 95243Am? How many electrons are present in the atom? How many nucleons may be considered as neutrons?
Q-8: Neutron was discovered by
a) Niels Bohr
b) J.Chadwick
c) J.J. Thomson
d) E.Goldstein
Q-9: Why did Rutherford choose gold foil for carrying out the alpha particle scattering experiment?
Q-10: Choose the pair of atoms with the same number of electrons in their outermost shell.
a) Na, Mg
b) Zn, Fe
c) Pn, Sb
d) K, Rb
Q-11: Fill in the blanks
a)The weighted average of the masses of all naturally occurring isotopes of that clement is equal to _________ of an atom.
b) The number of _________ in an atom’s nucleus equals the number of ______ in a neutral atom.
c) The _______ is where most of an atom’s mass is located.
d) The greatest possible sum of neutrons and protons in a hydrogen isotope is ________
e) Inside the atom, only certain special orbits known as _____ of electrons are permitted.
Q-12: What did Rutherford’s scattering experiment reveal about the structure of an atom?
a) Most of the space inside an atom is empty
b) Electrons move in a circular path of fixed energy called orbits
c) the centre of an atom has a small dense nucleus
d) the majority of an atom’s mass is concentrated in the centre.
Q-13: Which of the following atomic properties could be correctly explained by the Thomson model of atom?
a) Atom stability
b) H-atom spectrum
c) Overall neutrality of an atom
d) Position of electrons, protons, and neutrons in an atom
Q-14: Symbols 1735Cl and 35Cl can be written whereas symbols 3517Cl and 35Cl are not acceptable. Answer briefly.
Q-15: a) Write the distribution of electrons in argon and phosphorus atoms.
b) If K and M shells contain 2 and 8 electrons respectively. How many electrons are present in the L shell?
Q-16: The distribution of electrons in different atomic orbits was proposed by
a) John Dalton
b) Bohr and Bury
c) Henry Moseley
d) Rutherford
Q-17: Describe the two postulates proposed by Neils Bohr in order to overcome the objections raised against Rutherford’s atomic model.
Q-18: An element is defined by which of the following subatomic particles?
a) electron
b) neutron
c) proton
d) electron + proton
Q-19: Which of the following statements about electron configuration is correct?
a) The electron configuration displays the occupancy of orbitals rather than their number.
b) electron configuration represents the outer orbitals of electrons in an atom
c) Electron configuration depicts the specific orbitals occupied by electrons in an atom
d) The shape of the orbitals is determined by electron configuration.
Q-20: The atomic structure of a silicon atom is depicted in the figure below. Please respond to the following questions.
i) What is the atomic weight of an atom of silicon?
ii) What is the atomic number of an atom of silicon?
iii) How many valence electrons are there in a silicon atom?
iv) How many electrons exist in a silicon atom?
v) Silicon atoms orbiting electrons are arranged in shells. How many shells are there?
Download the PDF to access answers to the Chemistry Worksheet for Class 9 Chemistry Chapter 4 Structure of the Atom Set – 2
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Read Also:
- Atoms and Molecules
- Rutherford’s Atomic Model and Limitations
- Thomson’s Atomic Model
- Thomson’s Atomic Model and its Limitations
- Class 9 Structure of the Atom MCQ
- Class 9 Structure of the Atom Important Questions with Answers
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