English Medium Class 9 - CBSE Question Bank Solutions for Science

Define soil erosion. Give its causes, effects and preventive measures.

Mention briefly the role of decomposers of cycling of materials.

What is the maximum number of electrons which can be accommodated in the K shell of an atom?

What is the maximum number of electrons which can be accommodated in the L shell of an atom?

What is the maximum number of electrons an M shell of the atom can accommodate?

What is the maximum number of electrons that can go into the N shell of an atom?

What is the maximum number of electrons which can be accommodated in the :
(a) innermost shell of an atom?
(b) outermost shell of an atom?

What is the Electronic Configuration of a Hydrogen Atom?

State the number of electrons present in the outermost shell of the atoms of the following elements :(i) Neon 
(ii) Chlorine

Which shell of an atom can accommodate a maximum of :
(a) 8 electrons ?
(b) 32 electrons ?

Name the shell of an atom which can accommodate a maximum of :
(a) 2 electrons ?
(b) 18 electrons ?

What do you understand by the term "electronic configuration" of an element? Write down the electronic configuration of oxygen (At. No. = 8).

An element has atomic number 13 and an atomic mass of 27.
(a) How many electrons are there in each atom of the element ?
(b) How are these electrons distributed in the various energy levels ?

Write the distribution of electrons in an atom of element whose atomic number is 18. What is special about the outermost electron shell (or valence shell) of the atom of this element?

Which of the following is the correct electronic configuration of sodium?

Which of the following represents the correct electron distribution in magnesium ion?

The correct electronic configuration of a chloride ion is :

From the Symbol `""_15^31"P"`, State : Electron Configuration of Phosphorus.

The atom of an element X has 7 electrons in its M shell.
(a) Write the electronic configuration of element X.
(b) What is the atomic number of element X?
(c) Is it a metal or a non-metal?
(d) What type of ion will be formed by an atom of element X? Write the symbol of the ion formed.
(e) What could element X be?

Magnesium and oxygen combine in the ratio of 3 : 2 by mass to form magnesium oxide. What mass of oxygen gas would be required to react completely with 24 g of magnesium ?