GSEB Solutions for Class 8 Science and Technology – Molecular Structure

GSEB Solutions for Class 8 Science and Technology – Molecular Structure (English Medium)

GSEB SolutionsMathsScience
Exercise 15:

Solution 1(a):

In the solar system, the Sun is present at the centre, likewise, in the atomic structure, the nucleus is present at the centre. All planets are revolving around the sun in a definite path; in the same way, electrons are revolving around the nucleus in various orbits.

Solution 1(b):

Sun is the centre of the solar system while the nucleus is the centre of an atom.

Solution 1(c):

Planets are rotating around the sun in the solar system while electrons are rotating around the nucleus in an atom.

Exercise 16:

Solution 1(a):

Element	Symbol	Atomic Number	No. of Protons	Electrons
Beryllium	Be	4	4	4
Boron	B	5	5	5
Carbon	C	6	6	6
Nitrogen	N	7	7	7
Oxygen	O	8	8	8
Fluorine	F	9	9	9
Neon	Ne	10	10	10
Sodium	Na	11	11	11
Magnesium	Mg	12	12	12
Aluminium	Al	13	13	13
Silicon	Si	14	14	14
Phosphorus	P	15	15	15
Sulphur	S	16	16	16
Chlorine	Cl	17	17	17
Argon	Ar	18	18	18
Potassium	K	19	19	19

Exercise 20:

Solution 1.1:

• Electron.

Electrons revolve around the nucleus in orbits.

Solution 1.2:

• Electron.

Electrons revolve around the nucleus in orbits.

Exercise 21:

Solution 1.3:

• Neutron.

Neutrons are electrically neutral; so, they do not carry any charge.

Solution 1.4:

• 18.

Third energy level can accommodate maximum 18 electrons.

Solution 2:

• Molecule – Atom:

Atom	Molecule
Atom is the smallest particle in an element.	Molecules are formed by the combination of two or more atoms.
It is not possible to breakdown the atom further.	Molecules can be subdivided to individual atoms.

• Atom – Ion:

Atom	Ion
An atom is neutral.	An ion has positive or negative charge.
An atom has same number of protons as electrons.	An ion has different number of protons and electrons.

Solution 3.1:

In an atom, the number of protons and electrons are equal. Since the positive and negative charges are equal, an atom is neutral with respect to the electrical charge.

Solution 3.2:

Elements consist of individual atoms. Each element always consists of the same type of atom which imparts its own unique properties to that element; so, basic unit for an element is atom. Compound consists of the smallest unit which contains at least two different types of atoms joint together by chemical bonds; so, the basic unit for compound is molecule.