Advance Concepts Chemistry

Q: How many valence electrons does an oxygen atom have?

(a) :  2
(b) :  6
(c) :  8
(d) :  16
(e) :  None of the Above
Answer:  6
Explanation:  The number of outer orbital electrons is represented by the group number in this case VI A.

Q: Which of the following is least inert?

(a) :  Helium
(b) :  Neon
(c) :  Argon
(d) :  Xenon
(e) :  None of the Above
Answer:  Xenon
Explanation:  Xenon has been shown to form several compounds including XeF6,XeF4 and XeF2.Ionization energies increase with decreasing atomic number.Although KrF2 is known ,stable compounds of the other noble gases are unknown and unexpected.

Q: Which of the following electronic configurations represent the electron configuration for a magnesium cation … Mg2+?

(a) :  1s2 2s2 2p6 3s3
(b) :  1s2 2s2 2p6 3s3 3p2
(c) :  1s2 2s2 2p6
(d) :  1s2 2s2 2p4
(e) :  None of the Above
Answer:  1s2 2s2 2p6 3s3
Explanation:  The magnesium cation is isoelectronic with neon ,an inert gas and is more stable because of this electron configuration.

Q: A liquid boils at a temperature of 100⁰C, which property of the liquid proves that it is pure water?

(a) :  It does not leave a residue when boiled.
(b) :  It freezes at 0⁰C.
(c) :  Its pH is nearly neutral.
(d) :  It turns white anhydrous copper(II) sulphate blue.
(e) :  None of the Above
Answer:  Its pH is nearly neutral.
Explanation:  A pure substance has a fixed melting and boiling point at the same atmospheric pressure.

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