NCTB Class 8 Science Chapter 6 The Structure of Atoms Solution
Bangladesh Board Class 8 Science Solution Chapter 6 “The Structure of Atoms” Exercises Question and Answer by Experienced Teacher.
NCTB Solution Class 8 Chapter 6 “The Structure of Atoms”
|NCTB Bangladesh Board|
The Structure of Atoms
Fill in the blanks
(1) According to the opinion of —— atoms are indivisible.
(2) Most of the mass of the atom is in the ——–.
(3) Most of the space of the atom is ——-.
(4) The number of —— in a atom is called atomic number.
(5) The number of protons in the isotopes of an element is ——.
Short answer questions:-
Atoms are formed by electrons, protons and the neutrons. At the centre of the Atom there exists the nucleus, in it there are protons with positive charge and neutrons without charge. At the orbit of the Atom there is electrons with negative charge.
The atomic number of Nitrogen is 7, it means the number of proton is Nitrogen atom is 7. As the number of protons is equal to the number of electrons then the number of electrons in Nitrogen atom is 7. The distribution of electrons is in order 2,5.
(3) Isotopes are used in the diagnosis and treatment of diseases. The affected cell of a cancer patient can be determined by sending radioactive isotopes, again radioactive isotope can be used to destroy the cancer affected cells.
In agriculture, the radiation from isotopes are used to control insects, it can be used to find out what type of fertilizer and what amount of fertilizer is needed for a specific crop.
(4) Let us consider sodium atom and fluorine atom. We know sodium atom has 11 electrons (2, 8, 1). For stability it needs 2 electrons in the outermost orbit. It can either lose 1 electron from 3rd orbit or can grabs 1 extra electron to complete the 3rd orbit. By losing 1 electron it becomes positively charged and it forms cation.
Flourin atom has 9 electrons (2,7). For stability it needs & electrons in the outermost orbit. After receiving one electron from outside it becomes negatively charged and it forms anion.
Multiple choice questions:
(1) (b) 8 – Electrons can stay in the second orbit of an atmos.
(2) It can be concluded from the experiment of Rutherford that – (b) (iii)
(3) The mass number of the atom is – (c) 18
(4) This element is – (d) Neon.
(1) (a) There are three isotopes of carbon.
(b) The atom which lose electrons and becomes positively charged called cation.
(c) The mass number of atom Y is (17+18) = 35 (17= atomic number = number of proton and 18 = number of neutron)
(d) The atomic number of X = 1, it means this atom has 11 protons, 11 electrons. The distribution of the electrons is in order (2, 8, 1).
The atomic number of Y = 17, it means this atom has 17 protons, 17 electrons. The distribution of the electrons is order (2, 8, 7)
According to the distribution of electrons of atom X, it can either lose 1 electron to from 3rd orbit or can grabs. 1 extra electron to complete 3rd orbit. And other hand atom Y can either lose 7 electrons or can grabs 1 extra electron to complete for 3rd orbit. So if atom X lose 1 electron and atom Y grabs this electron from atom X then they can bond between them.
(2) (a) The word atom means a tiny particle of a matter.
(b) When it is said that the atomic number of oxygen is 8, this means the number of protons in oxygen atom is 8.
(c) Fig-1 of stimulus has 11 electrons in order (2, 8, 1) that means its 3rd orbit is not complete. So it always has a tendency to lose 1 electron to fulfil the last orbit for stability. That’s why it is active.
(d) Number 1: According to the atomic structure of no. 1 atom, there are 11 electrons in the order and as we know in an atom, electron’s number = proton’s number so, there are 11 protons. The atomic number of this atom is 11.
Number 2: According to the atomic structure of no. 2 atom, there are 1 electron and 1 proton. The atomic number of this atom is 1.