CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
In calcium oxide, CaO, what is the valency of calcium?
A. 3
B. 1
C. 4
D. 2
Correct Answer: D
Calcium forms Ca2+ and oxygen forms O2−, producing a 1:1 formula.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
Which term is more precise than fixed valency for transition metals that can form ions with different charges?
A. Boiling point
B. Atomic radius only
C. Isotope number
D. Oxidation state
Correct Answer: D
Transition metals often exhibit multiple oxidation states.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is the valency of magnesium in magnesium chloride, MgCl2?
A. 2
B. 3
C. 1
D. 4
Correct Answer: A
Magnesium forms Mg2+ and has valency 2 in this compound.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is the valency of sodium in sodium chloride?
A. 1
B. 2
C. 0
D. 3
Correct Answer: A
Sodium loses one valence electron to form Na+.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
Why do noble gases generally have valency zero in elementary descriptions?
A. Their outer electron shells are already stable and complete
B. They are all metals
C. They have no nuclei
D. They contain no electrons
Correct Answer: A
Closed-shell electron configurations make noble gases relatively unreactive.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is the usual valency of carbon in methane, CH4?
A. 2
B. 3
C. 1
D. 4
Correct Answer: D
Carbon forms four covalent bonds in methane.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is the usual valency of nitrogen in ammonia, NH3?
A. 1
B. 3
C. 2
D. 4
Correct Answer: B
Nitrogen forms three N−H bonds in ammonia.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is the usual valency of oxygen in many compounds?
A. 2
B. 1
C. 4
D. 3
Correct Answer: A
Oxygen commonly forms two bonds or gains two electrons in ionic compounds.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is the usual valency of hydrogen in many compounds?
A. 1
B. 2
C. 3
D. 4
Correct Answer: A
Hydrogen commonly forms one bond.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Valency
What is valency in elementary chemistry?
A. The atomic mass only
B. The number of neutrons only
C. The melting point
D. The combining capacity of an atom
Correct Answer: D
Valency describes how many electrons an atom tends to lose, gain or share in bonding.