Selina solutions concise chemistry class 9 icse Solutions for Chapter 5 chapter 5 the periodic table

Explain ‘Newland’s law of Octaves.’ Why was the law discarded?

Why did Mendeleev leave some gaps in his periodic table of elements ? Explain your answer with an example.

The atomic number of an element is more important to the chemist than its relative atomic mass. Why?

Consider the following elements: Be, Li, Na, Ca, K. Name the elements of

(a) same group

(b) same period.

a) State the modern Periodic table law.

b) How many periods and groups are there in the modern periodic table

What are the main characteristics of the last elements in the periods of a periodic table? What is the general name of such elements?

What is meant in the periodic table by :

(a) a group, and

(b) a period

a) What are the following groups known as?

(i) Group 1

(ii) Group 17

(iii) Group _18

(b) Name two elements of each group.

How does the number of

i) Valence electrons

ii) valency vary on moving from left to right

a) In the second period of a periodic table

b) In the third period of a periodic table

How do atomic structures (electron arrangement) change in a period with an increase in atomic numbers, moving left to right?

In which part of a group would you separately expect the elements to have

(a) the greatest metallic character?

(b) the largest atomic size

The position of elements A, B, C, D, and E in the periodic table is shown below

(a) State which is metals, non-metals, and noble gas in this table.

(b) State which is the most reactive (i) metal (ii) non-metal

(c) Which type of ion will be formed by element A, B, and C.

(d) Which is larger in size (i) D or E (ii) B or C.

Element P has atomic number 19. To which group and period. does P belong? It is a metal or a nonmetal? Why

Name or state the following with reference to the element of the first three periods of the periodic table.

(a) Noble gas with duplet arrangement of electrons.

(b) Metalloid in Period 3.

(c) Valency of elements in Group 14 and 15.

(d) Noble has had electronic configuration 2, 8, 8.

(e) Group whose elements have zero valencies.

(f) A covalent compound formed by an element in p 2 and a halogen.

(g) Non-metallic elements present in Period 3 of Groups 15 and 16.

(h) An electrovalent compound formed by an alkaline earth metal and a halogen.

(i) Bridge elements of Period 3 of Group 1, 2, and 3,

(j) Alkali metal in Period 3 that dissolves in the water giving a strong alkali.

(k) Typical elements of Groups 14 and 15.

(1) Alkaline earth metal in Period 3.

Match the Column A with Column B

Write down the word that will correctly complete the following sentences:

a) Ralative atomic mass of a light element up to calcium is approximately ……….. its atomic number.

b) The horizontal rows in a periodic table are called ………

c) Going across a period left to right, atomic size………..

d) Moving left to right in the second period, number of valence electrons…….

e) Moving down in the second group, number of valence electrons …………

a) Name the method by which alkali metals can be extracted.

b) What is the color of the flame of Sodium and Potassium?

(a) How do alkaline earth metals occur in nature?

(b) Write the electronic configuration of the first two alkaline earth metals.

Arrange the following

(a) Elements of group 1, in increasing order of reactivity.

(b) Elements of group 17, in decreasing order of reactivity.

(c) He, Na, Mg (increasing order of melting point).

(d) Chlorine, sodium, magnesium (increasing reducing character).

(a) State the nature of compounds formed when group 17 elements combine with (i) metals (ii) nonmetals.

(b) Why group 17 elements are highly reactive?

Name the gas used in

(a) filling balloons

(b) light bulbs

(c) bright colored advertising light works

(a) What is the name given to group 17 elements? Why are they called so?

(b) Comment on the (i) reactivity (ii) color and (iii) physical state of group 17 elements

Two elements P’ and `Q’ belong to the same period of the modern periodic table and are in group 1 and

group 2 respectively. Compare the following characteristics in tabular form.

(a) a number of electrons in their atoms.

(b) their tendency to lose electrons.

(c) their metallic characters.

(d) formation of their oxides.

(e) formulae of their chlorides.