Chemistry Multiple Choice Questions on “Periodic Trends in Properties of Elements”.
1. Atomic radii ____________ along the periods.
a) Increases
b) Decreases
c) Remains constant
d) Irregular
Answer: b
Clarification: Atomic radii decreases along the periods because as the number of electrons increases in the same shell of the atom, the effective nuclear attraction increases, thereby reducing the distance between the outer shell and the nucleus i.e. decreasing atomic radii.
2. O2-, F–, Na+ and Mg2+ are called as __________
a) Isoelectronic species
b) Isoneutral species
c) Isotopes
d) Isobars
Answer: a
Clarification: O2-, F–, Na+ and Mg2+ are known as isoelectronic species as they all have the same no. of electrons(10). Isotopes contain the same no. of protons but a different number of neutrons. Isobars have the same mass number but a different atomic number.
3. X(g) → X+(g) + e–. What does this chemical reaction need to occur?
a) Catalyst
b) Electron affinity
c) Electropositivity
d) Ionization energy
Answer: d
Clarification: The minimum amount of energy that is required to remove an electron from an atom is called Ionization enthalpy. It is expressed in the units KJ/mol. Electron affinity is the change in the energy when we add an electron to a neutral atom. Electropositivity is a metallic characteristic. A catalyst speeds up the reaction.
4. What is the correct order of electronegativity among the following options?
a) Li
d) Li>Na>K=Rb>Cs
Answer: d
Clarification: Electronegativity is the measure of the ability to attract shared electrons to itself of an atom in a chemical compound. The values of electronegativities of Li, Na, K, Rb and Cs are 1, 0.9, 0.8, 0.8 and 0.7 respectively.
5. Ionization energies are always positive.
a) True
b) False
Answer: a
Clarification: As the ionization energy is the minimum amount of energy that is required to remove an electron from an atom. As the energy is always needed for the removal of an electron from an atom, the values of ionization energies are always positive.
6. What is the oxidation state of Mn in KMnO4?
a) 5
b) 6
c) 7
d) 4
Answer: c
Clarification: The total charge of the compound KMnO4 is zero as it is a neutral and stable compound. As we know the oxidation states of K and O are +1 and -2 respectively. So +1 + Mn charge + 4(-2) = 0; Mn charge = 7.
7. The relationship between Li, Mg and Be, Al is called the __________ relationship.
a) Diagonal
b) Periodic
c) Group
d) Triangle
Answer: a
Clarification: The Elements Li and Mg, Be and Al are similar to each other in the case of formation of different compounds in a similar composition. They have a sort of similar behaviour with each other, so they are said to be in a diagonal relationship as per their place in the periodic table.
8. N2O is a _________
a) Tear gas
b) Laughing gas
c) Acid
d) Base
Answer: c
Clarification: N2O is called laughing gas as it has euphoric effects after being inhaled. It is one of the World Health Organization’s Essential Medicines. it is used for recreational and anaesthetic purposes mostly.
9. Which of the following is superoxide?
a) K2O
b) Na2O
c) MgO
d) KO2
Answer: d
Clarification: In the superoxide of the element, the oxygen’s oxidation state is given by -1/2. In peroxides, the oxidation state of oxygen is -1 as in case of hydrogen peroxide. The oxygen’s oxidation state in KO2 is -1/2.
10. What can be tested using a litmus paper?
a) Acidic nature only
b) Basic nature only
c) Both acidic nature and basic nature
d) Nothing
Answer: c
Clarification: A litmus paper is a dye that is extracted from lichens. It used to test acidic nature and basic nature of a substance. Red colour indicates acidic nature and blue colour indicated basic nature. Neutral litmus paper is purple in colour.