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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.