Page 90 - ICSE Chemistry 8

A covalent bond is formed by the sharing of electrons between non-metals.

Oxygen molecule: Oxygen atom (2,6) combines with another oxygen atom by sharing two electrons
to form oxygen molecule.

O O O O

Oxygen atom (2,6) + Oxygen atom (2,6) Oxygen molecule

Take a Break!

Write/Choose the correct answer.

1. Name the subatomic par cles of an atom.
2. The extra-nuclear region of an atom consists of electrons. (True/False)
3. Atomic number is the number of neutrons present inside the nucleus of an atom. (True/False)

4. The sum total of ___________ and ___________ is known as mass number of an element.
5. If the atomic number of nitrogen is 7, then the number of protons present in it will also be 7.
(True/False)
6. If the mass number of aluminium is 27 and its atomic number is 13, then the number of neutrons
present in it would be _____________.
7. The _____________ of an element have same atomic number.
8. The outermost shell of an atom can accommodate _____________ electrons.

9. Oxygen donates two electrons and becomes an oxygen ion. (True/False)
10. Ammonium is an example of a radical. (True/False)
11. A _____________ is formed when two atoms combine.

12. A _____________ bond is formed by the sharing of electrons.

Terms to Know

Discharge tube: A cylindrical glass tube with sealed electrodes at each end

Cathode: A metal plate connected to the nega ve terminal of the voltage source
Anode: A metal plate connected to the posi ve terminal of the voltage source

Cathode rays: A stream of rays originated from the cathode

Electrons: Nega vely charged par cles that revolve around the nucleus in fi xed energy
shells

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