Chapter 2 · Model test40 marks · 1½ hours

Model Test Paper മാതൃകാ ചോദ്യപേപ്പർ

A full paper in the Kerala Class 9 Chemistry pattern, covering the whole of “Periodic Table” – Mendeleev’s and the modern periodic law, periods and groups, families, finding the group and period from the electron configuration, main group elements, noble gases, transition elements, lanthanoids and actinoids, and the size of atoms. Work on paper with a timer before you look at the solutions.

✍️ Attempt first!

Set a timer for 15 minutes of reading (cool-off time) and then 1½ hours of writing. Do not look at the periodic table while you write – the paper tests whether you can find groups and periods yourself. The fully solved paper, with animated shell diagrams and table pictures and marking hints, is on the next page.

Standard IX · Chemistry

Chapter 2 · പീരിയോഡിക് ടേബിൾ · Periodic Table

Time: 1½ hours (+ 15 min cool-off time)Total: 40 marks

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.
Write electron configurations like 2, 8, 1. When you find a group or a period, show how you found it.
When you compare the sizes of atoms, always give the reason.

SECTION AAnswer all · 8 × 1 = 8 marks

According to the modern periodic law, the chemical and physical properties of elements are periodic functions of their

(a) atomic masses(b) atomic numbers(c) numbers of neutrons(d) mass numbers

(1)

The elements of groups 3 to 12 of the periodic table are called .

(1)

How many elements are there in period 6 (counting the lanthanoids)?

(a) 8(b) 18(c) 32(d) 15

(1)

Find the relation and fill in: sodium : alkali metals :: neon :

(1)

The electron configuration of an element is 2, 8, 18, 7. The number of the period to which it belongs is .

(1)

Pick the odd one out and give the reason: iron, copper, magnesium, zinc

(1)

Which of these atoms is the largest?

(a) beryllium (Be)(b) magnesium (Mg)(c) calcium (Ca)(d) strontium (Sr)

(1)

Which of the following is a metalloid?

(a) sodium(b) silicon(c) sulphur(d) argon

(1)

SECTION BAnswer all · 5 × 2 = 10 marks

The atomic number of an element X is 15. (a) Write its electron configuration. (b) Find its period number and group number. Give the reasons.

(2)

10.

In the periodic table, argon (atomic mass 40) comes before potassium (atomic mass 39). (a) Why is this a limitation of Mendeleev’s periodic table? (b) How does the modern periodic table remove this problem?

(2)

11.

Krypton (Z = 36) has the electron configuration 2, 8, 18, 8. (a) Find its group number and period number. (b) Why does krypton normally not take part in chemical reactions?

(2)

12.

Write the family name of the elements of each group: (i) group 2 (ii) group 13 (iii) group 16 (iv) group 17

(2)

13.

Helium (2) has 2 electrons in its outermost shell, just like beryllium (2, 2). (a) Why is helium placed in group 18 and not in group 2? (b) Why does period 1 have only two elements?

(2)

SECTION CAnswer all · 4 × 3 = 12 marks

14.

The atomic numbers of three elements P, Q and R are 6, 14 and 32. The electron configuration of R is 2, 8, 18, 4. (a) Write the electron configurations of P and Q. (b) Do P, Q and R belong to the same group? Find the group and name the family. (c) Which of them has the largest atom? Why?

(3)

15.

The electron configurations of three consecutive elements X, Y and W of period 4 are: X 2, 8, 14, 2; Y 2, 8, 15, 2; W 2, 8, 16, 2.
(a) Find their atomic numbers. (b) In which shell is the new electron added as we go from X to Y to W? What type of elements are these? (c) X, Y and W are in different groups, yet they show similar chemical properties. Why?

(3)

16.

Complete the table.

Element	Atomic number	Electron configuration	Period	Group
Nitrogen	7	(i) ……	(ii) ……	15
Calcium	20	2, 8, 8, 2	4	(iii) ……
Gallium	(iv) ……	2, 8, 18, 3	(v) ……	(vi) ……

(3)

17.

(a) Which is larger: a lithium atom (2, 1) or a potassium atom (2, 8, 8, 1)? (b) The nuclear charge of potassium (+19) is much greater than that of lithium (+3). Why is the potassium atom still larger? (c) Which is larger: a boron atom (2, 3) or a fluorine atom (2, 7)? Give the reason.

(3)

SECTION DAnswer all · 2 × 5 = 10 marks

18.

The figure shows a part of the periodic table. The letters are not the real symbols of the elements.

(a) Which two elements are halogens? To which family does D belong?
(b) Write the electron configuration of J. Show how its group number is found from it.
(c) Find the atomic number of Q. Why is Q called a transition element?
(d) G and M show similar chemical properties. Why?
(e) Arrange G, J and L in the increasing order of atomic size. Give the reason.

(5)

19.

Read the passage and answer the questions.

After floods, wells in many parts of Kerala are disinfected with potassium permanganate (KMnO₄), a deep purple compound of manganese (Z = 25). Arecanut farmers spray Bordeaux mixture – blue copper sulphate (copper, Z = 29) mixed with white lime, a compound of calcium (Z = 20) – to protect the palms from മഹാളി (koleroga). On the beaches of Chavara in Kollam, the black mineral sand ilmenite is used to make titanium (Z = 22) dioxide at KMML, and monazite sand is a source of the rare earths.

(a) The configurations are: titanium 2, 8, 10, 2; manganese 2, 8, 13, 2; copper 2, 8, 18, 1. In which period are these elements? Give the reason.
(b) Potassium permanganate is purple and copper sulphate is blue. Which property of transition elements does this show? Lime is white – why?
(c) Calcium has the configuration 2, 8, 8, 2. Find its group number and name its family.
(d) Compare the configurations of titanium and manganese. In which shell are the extra electrons of manganese added? How many outermost electrons does each have?
(e) The rare earths obtained from monazite are lanthanoids. Which elements are the lanthanoids, and where are they placed in the periodic table?

(5)

*** End of the question paper ***

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