Question
Three properties of element X are listed.
● It contains atoms with a full outer shell of electrons.
● It is monoatomic.
● It is unreactive.
In which part of the Periodic Table is the element placed?
A. Group I
B. Group VII
C. Group VIII
D. transition elements
▶️Answer/Explanation
Ans:
C
All these properties correspond to noble gases in group VIII.
Question
A flammable gas needs to be removed from a tank at an industrial plant. For safety reasons, an inert gas is used.
Which gas is suitable?
A argon
B hydrogen
C methane
D oxygen
▶️Answer/Explanation
Ans:A
Argon is a noble gas which is inert.
Question
A balloon is filled with helium. Helium is a noble gas and makes the balloon rise up in the air.
The density of air is $1.23 \mathrm{~g} / \mathrm{dm}^3$.
Which gas is helium?
▶️Answer/Explanation
Ans:B
It is lighter than air. Its density is $0.179 \mathrm{~g} / \mathrm{dm}^3$. It is an inert gas and hence does not react with oxygen.
Question
Why is helium used to fill balloons?
A Helium is monoatomic.
B Helium is in Group VIII of the Periodic Table.
C Helium has a full outer electron shell.
D Helium is less dense than air.
▶️Answer/Explanation
Ans: D
Helium is less dense than air. Hence, Helium is used to fill balloons.
Question
The noble gases are in Group VIII of the Periodic Table.
Which statement explains why noble gases are unreactive?
A They all have eight electrons in their outer shells.
B They all have full outer shells.
C They are all gases.
D They are all monoatomic.
▶️Answer/Explanation
Ans: B
Noble gases are unreactive because they all have fully filled outer shells.