INDIAN SCHOOL AL WADI AL KABIR
DEPARTMENT OF SCIENCE-2017-18
CLASS-9-CHEMISTRY
WORKSHEET-STRUCTURE OF ATOM
Basic level questions (1 mark)
1. Which of the following forms metallic ion?
Sodium,carbon,oxygen,sulphur
2. Define atomic number.
3. Define mass number.
4. There are 15 protons and 16 neutrons in the nucleus of an element. Calculate its atomic number and mass number.
5. What are isobars?
Intermediate level questions (2 or 3 marks)
6. Which of the following elements have same number of valence electrons?
N (7), O(8),F (9), P(15) and Cl(17)
7. What information is conveyed by the statement that the mass number of sulphur is 32 and
the atomic number is 16?
8. With the help of labelled diagram write two main proposals of Thomson’s model of atom.
9. The electronic configuration of an element X is 2,8,2
(i) Find the number of electrons present in the atom of element X
(ii) Write its atomic number?
(iii) Is element X a metal or a non-metal?
(iv) Find out the valency of X
10. You are given an element 816X.Find out
(i) Number of protons, electrons and neutrons in X
(ii) Valency of X
(iii) The chemical formula of the compound that this element forms with Sodium
Advanced level questions (3 or 5 marks)
11. In the following table, the mass number and atomic number of certain elements are given:
Element / A / B / C / D / E / F / G / HMass No. / 2 / 3 / 3 / 6 / 9 / 11 / 19 / 23
Atomic No. / 1 / 1 / 2 / 3 / 4 / 5 / 9 / 11
i. How many neutrons are present in F?
ii. Which atoms are isotopes of the same element? Which atom will form singly charged positive ion? Page 1 of 2
iii. Which is the atom of an inert gas?
iv. Which will form a singly charged negative ion?
v. Which of these has 11 electrons?
12. (i) Why chemical properties of all the isotopes of an element are same?
(ii) Name the isotopes used in the treatment of goitre and cancer.
(iii)An element X has 2 electrons in its M shell. What is its atomic number?
13. Give reasons for the following:
(a)40Ar and 40Ca are called isobars.
(b)He and Ne have zero valency.
(c)An atom is electrically neutral.
(d)Nucleus of an atom is positively charged.
(e)Isotopes have similar chemical properties.
14. Describe Rutherford’s α-particle scattering experiment and mention the important observations and conclusions from this experiment.
Previous year CBSE board based questions
15. Which atom, Na+ or He, has completely filled K and L shells? Give reason to support your answer.(2 marks)
16. (i) Both Helium and Beryllium have two electrons in the valence shell. Helium is a noble gas whereas Beryllium is a metal, justify.
(ii) Hydrogen exists in three isotopic forms. Why are the isotopes of hydrogen chemically alike?(3 marks)
17. (i) Define valency. What conclusions can be drawn about the reactivity of an atom from its valency?
(ii) Why does an atom of Argon have zero valency? Explain using the electronic configuration of Argon. (3 marks)
18. An atom has 2 electrons in its outermost shell M. What is the atomic number of the element? Also mention its name. (1 mark)
19. Give reasons for the following:
(i) An atom is electrically neutral.
(ii) Noble gases show least reactivity.
(iii) Nucleus of an atom is heavy and positively charged.
(iv) Ions are more stable than atoms. (5 marks)
Higher order thinking skill questions
20. If the electronic configuration of a neutral atom Z is 2,8,6 What will be the electronic configuration of Z2-?
21. An element is represented as yyX. Identify the element.
22. A dinegative ion of an element X has the electronic configuration 2,8. Identify X.
Prepared by Ms. Asha John Page 2 of 2