Model Test Paper മാതൃകാ ചോദ്യപേപ്പർ
A full paper in the Kerala Class 9 Chemistry pattern, covering the whole of “Structure of the Atom” – discharge tubes, cathode and canal rays, the electron, proton and neutron, the atom models of Thomson, Rutherford and Bohr, atomic number and mass number, electron configuration and orbit diagrams, isotopes and isobars, and the uses of radioactive isotopes. Work on paper with a timer before you look at the solutions.
Standard IX · Chemistry
Chapter 1 · ആറ്റത്തിന്റെ ഘടന · Structure of the Atom
- The first 15 minutes are cool-off time: read every question and plan your answers; do not write.
- Answer all questions. Marks for each question are shown on the right.
- Show your working for numerical questions (Z, A, number of neutrons). Write electron configurations like 2, 8, 1.
- In an orbit diagram, mark the numbers of protons and neutrons in the nucleus and draw the electrons on the rings.
SECTION AAnswer all · 8 × 1 = 8 marks
1.
The subatomic particle that has no charge is the
(1)(a) electron(b) proton(c) neutron(d) α particle
2.
Hydrogen gas is taken in a discharge tube with a perforated cathode. The positive particles of the canal rays it gives are the lightest of all. These particles are called .
(1)3.
The maximum number of electrons that the M shell can hold is
(1)(a) 2(b) 8(c) 18(d) 32
4.
Find the relation and fill in: electron : J. J. Thomson :: neutron :
(1)5.
How many neutrons are there in an atom of 3717Cl?
(1)6.
Pick the odd one out and give the reason: 168O, 178O, 188O, 147N
(1)7.
The charge of an electron, measured by Robert Millikan’s oil-drop experiment, is
(1)(a) 1.76 × 1011 C(b) 9.1 × 10−31 C(c) 1.6 × 10−19 C(d) 1.6 × 1019 C
8.
The radioactive isotope used to detect leaks in industrial pipelines is .
(1)SECTION BAnswer all · 5 × 2 = 10 marks
9.
(a) Using 2n², find the maximum number of electrons that the N shell can hold. (b) The electron configuration of calcium (Z = 20) is 2, 8, 8, 2, although the M shell can hold 18 electrons. Why is it not written as 2, 8, 10?
(2)10.
Ammu wrote these electron configurations in her science diary. Find the mistake in each and write the correct configuration.
(i) sodium (Z = 11): 2, 9 (ii) magnesium (Z = 12): 8, 4
(2)(i) sodium (Z = 11): 2, 9 (ii) magnesium (Z = 12): 8, 4
11.
Write two differences between cathode rays and canal rays.
(2)12.
J. J. Thomson proposed the plum pudding model of the atom. (a) Describe this model. (b) According to this model, why is the atom electrically neutral?
(2)13.
Rutherford’s atom model could not explain the stability of the atom. (a) Why? (b) How did Niels Bohr’s model overcome this limitation?
(2)SECTION CAnswer all · 4 × 3 = 12 marks
14.
The figure shows Rutherford’s gold foil experiment. Write the inference Rutherford drew from each observation.
(3)| Observation | Inference |
|---|---|
| (i) Most of the α particles passed straight through the gold foil without any deflection. | …………… |
| (ii) Some α particles were deflected by small angles. | …………… |
| (iii) Very few α particles (about 1 in 20 000) bounced back at 180°. | …………… |
15.
Complete the table.
(3)| Atom | Atomic number (Z) | Mass number (A) | Protons | Electrons | Neutrons |
|---|---|---|---|---|---|
| 94Be | 4 | 9 | (i) …… | 4 | (ii) …… |
| F | (iii) …… | (iv) …… | 9 | 9 | 10 |
| Ca | (v) …… | 44 | 20 | 20 | (vi) …… |
16.
The nucleus of an atom contains 12 protons and 14 neutrons. (a) Find its atomic number and mass number. (b) Write its electron configuration. (c) Draw its orbit (shell) diagram.
(3)17.
The numbers of protons and neutrons in the nuclei of three atoms P, Q and R are given.
P: 16 protons, 16 neutrons · Q: 16 protons, 20 neutrons · R: 18 protons, 18 neutrons
(a) Write the mass number of each atom. (b) Which two are isotopes? Why? (c) Which two are isobars? Why?
(3)P: 16 protons, 16 neutrons · Q: 16 protons, 20 neutrons · R: 18 protons, 18 neutrons
(a) Write the mass number of each atom. (b) Which two are isotopes? Why? (c) Which two are isobars? Why?
SECTION DAnswer all · 2 × 5 = 10 marks
18.
Read the passage and answer the questions.
(5)At the Regional Cancer Centre (RCC), Thiruvananthapuram, the radiation from cobalt-60 (6027Co) is used to treat cancer. Doctors use iodine-131 to study and treat diseases of the thyroid gland. Archaeologists find the age of fossils with carbon-14. In nuclear power stations uranium-235 is used as the fuel, and heavy water is also used there. Cobalt-60, iodine-131, carbon-14 and uranium-235 are all isotopes.
(a) What are isotopes? (b) Cobalt has atomic number 27. How many protons and neutrons are there in a cobalt-60 atom? (c) Which isotope of carbon is used to study life processes in plants and animals? Which isotope of carbon is the most abundant? (d) 146C and 147N have the same mass number. What are such atoms called? How many neutrons does each have? (e) Heavy water is the oxide of which isotope of hydrogen? How many neutrons are there in one atom of that isotope?19.
The orbit diagram of an atom X is given. (a) Write the atomic number and mass number of X. (b) Write its electron configuration. How many electrons are there in its outermost shell? (c) Which shell of X has the highest energy? (d) An electron of X jumps from the L shell to the M shell. Does it absorb energy or give out energy? (e) Using 2n², find the maximum number of electrons the M shell can hold. Why does X have only 4 electrons in it?
(5)*** End of the question paper ***