Rajasthan Board Class 10 Science Chapter 7 Solution Atomic Theory Periodic Classification and Properties of Elements RBSE Class 10 Science Solution for Chapter 7
Objective type of questions.
(1.) Which radiation Rutherford used in his experiments?
(2.) Which is the smallest particle of substance?
Ans- b) atom
(3.) Who gave first periodic classification of elements?
c) New land
(4.) On which property morden periodic table is based?
a) Atomic structure
b) Atomic weight
c) Atomic number
Ans-c) atomic number.
(5.) Number of periods and groups in modern periodic tables are
a) 7 and 8
b) 9and 19
c) 7 and 20
d) 9 and 20
Ans-a) 7and 8
(6.) In periodic table, on moving down a group atomic size
b) Remains constant
c) Remains irregular
(7.) Vanderwaal radius is —than covalent radius.
d) None of these
Ans- b) larger
(8.) In short period, number of elements are
(9.) Energy given to isolate electron from neutral atom is:
a) Electron gain enthalpy
c) Ionization enthalpy
d) Excitation energy
Ans-c) ionization enthalpy
(10.) Which element has highest electronegative
(11.) Members of which groups have highest metallic properties:
Very short type questions
(12.) Write the name of Thomson”s model?
Ans-Plum Pudding model
(13.) What are Bhor’s orbits called?
(14.) What is modern periodic law?
Ans- physical and chemical properties of elements are periodic function of their atomic number.=
(15.) Write Mendeleef’s periodic law?
Ans- properties of elements are periodic functions of atomic weight.it is the Mendeleef’s periodic law.
(16.) On the basis of which property Mendeleef kept elements in periodic order?
Ans-he arranged elements in increasing order of their atomic weight ans saw that after a fixed interval same properties of elements repeats.
(17.) What name was given to members of 18th group?
(18.) What are the other names of d-block and f- block elements?
Ans-d- block called transition elements
f-block called inner transition elements.
Short type questions.
(19.) Give the position of metals, non metals, and metalloids in the periodic table?
Ans-the metals are to the left of the periodic table, the non metals are to the right side of the periodic table and the elements immediately adjacent to the periodic table before the line is called metalloids. The zig zag ladder line between metals and non metals in the periodic table called metalloids.
(20.) Explain periodicity in electron gain enthalpy in a group?
Ans-it is also called electron affinity in gaseous state. When a neutral atom of nay element accepts an electron. Then negative ion is formed and the energy releases is called electron gain enthalpy or electron affinity.
(21.) What do you understand by Vanderwaal radius and Covalent radius?
Ans-the atomic size of the atoms is determined by radius
a) Vanderwaal radius in solid state half of the distance between atoms of two close non bonded molecules of same substance is called vanderwaal radius.
b) Covalent radius – when two same atoms of an elements are covalently bonded then half of the distance between nuclei of both atoms is called covalent radius.
The value of vanderwaal radius is always greater than covalent radius.
(23.) What is effective nuclear charges? How it change in a group and a period?
Ans- the charge on atom is known effective nuclear charge. In periods on going from left to right in a period as atomic size decreases and value of effective nuclear charge increases so it becomes difficult to isolate electron from the atom. This change is happened in periods.
Now on moving down a group number of shells increases so atomic size increases and due to decreases in effective nuclear charge, attraction of outer most electrons is less. So it is easy to separate electron form neutral atom. This change is happened in groups.
(24.) Valency shows which type of periodic property while going from left to right in a period?
Ans-the number of electrons present in the outer most shell of an elements determine valency of that element. the element of the same group shows the same valaency because electronic configuration of their outermost shell are same. On moving from left to right in a period the atomic size decreases and due to increases in effective nuclear charge, electron gain enthalpy increases.
(25.) Write Dalton’s theory of atomic structure?
Ans-atomic theory of Dalton :-
a) Each substance is made up of small particles which are called atoms
b) Atoms are indivisible particles.
c) All the atoms of an elements have different mass, size, and chemical properties.
d) Atoms of different elements always combine in simple proportion of small whole numbers to form compound.
e) In chemical reactions, atoms only rearrange they can neither be created nor be destroyed by chemical reactions.
Atomic theory of Dalton could not explain many facts but if it laid to strong fundamental of advanced research about the atoms on basis of scientific and experimental facts.
Essay type questions.
(26.) List merits and demerits of Mendeleef periodic table?
Ans-merits of Mendeleef’s periodic table:
a) He arranged periodic table in vertical columns and horizontal rows. He called the vertical colums as group and horizontal rows as periods.
b) His table had 8 groups which were divided in two sub groups. A and B till that time noble gas were not known and later to show them a new group called zero group was made.
c) Mendeleef arranged the elements in the table in the increasing order of atomic weight. He confirm that elements with same type of physical and chemical properties should come in the same group so that periodicity of elements is maintained.
d) He left gaps for EKa boron,Eka aluminium and predict their properties which were proved correct later. Later they were called scandium, gallium
e) This are the merits of mendeleef periodic table
- Demerits of mendeleef periodic table:
a) At some places increasing order of atomic weight was not followed.
b) Some elements with similar properties were kept in different groups and some elements with dissimilar properties in same group.
c) Hydrogen was not given fixed position.
d) Isotopes were not given any position
These are the demerits of mendeleef periodic table.
(27.) How the following properties of elements show periodicity in periodic table?
a) Atomic radius
b) Ionization enthalpy
Ans- a) atomic radius – the distance between nucleus and electron present in outermost shell of atom is called atomic radius. It is very small unit . in a period on moving from left to right atomic number increase thus number of protons increase so the atomic radius decreases. In group atomic no increases number of shells also increases so atomic radius is also increase.
b ) ionization enthalpy- the energy given to isolate an electron form a neutral atom of an element in gaseous state is called ionization enthalpy. due to this and nuclear effective charge in period moving from left to right atomic size decrease. And in group moving down the atomic size increases.
C ) electronegativity- the property of attracting of chemical bond formed between two different atoms by an atom is called electronegative. On moving from left to right ina period due to decreases on atomic size electronegative of elements increases. On moving down a group atomic size increases so value of electronegative decreases.
This property shows periodicity in periodic table.
(28.) Explain classification of elements by modern periodic table.
Ans- the elements are classified in four blocks. Group 1and 2 are called s- block elements, group 13 and 18 are p-block elements, group 3to 12 are d- block elements and at the bottom both horizontal rows are called f- block elements.
Elements of s- block are called alkali or alkaline Earth metal, p-block are called principle elements, d- block are called transition elements and elements of f- block are called inner transition elements .
In this way in periodic table electropositive metallic elements are placed at left and electronegative non –metallic elements on the right. The metals are between metal and non metals are called metalloids.