Classification of Elements and Periodicity in Properties
- Which of the following statements are true?A. Unlike Ga that has a very high melting point, Cs has a very low melting point.B. On Pauling scale, the electronegativity values of N and Cl are not the same.C. Ar, K^+, Cl^-, Ca^2+, and S^2- are all isoel… Answer: 2. C and E only Key idea: check each statement separately. A false: gallium melts at only about 30 °C, so it does not have a very hi... 1
- Which among the following electronic configurations belong to main group elements?A. [Ne]3s^1 B. [Ar]3d^3 4s^2 C. [Kr]4d^105s^2 5p^5 D. [Ar]3d^104s^1 E. [Rn]5f^0 6d^2 7s^2Choose the correct answer from the option given below : Answer: 2. A and C only Key idea: main group elements are s- and p-block elements; d-block elements have d electrons being filled. A: [Ne]3s... 1
- Arrange the following elements in increasing order of first ionization enthalpy:Li, Be, B, C, NChoose the correct answer from the options given below: Answer: 3. Li < B < Be < C < N Key idea: ionization enthalpy increases across a period, with exceptions at Be (filled 2s) and N (half-filled... 1
- Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :Assertion A : Metallic sodium dissolves in liquid ammonia giving a deep blue solution, which is paramagnetic.Reasons R : The deep blue solution is… Answer: 4. A is true but R is false. Key idea: Sodium in liquid ammonia gives ammoniated electrons. Na + (x+y)NH₃ → [Na(NH₃)_x]^+ + [e(NH₃)_... 1
- The element expected to form largest ion to achieve the nearest noble gas configuration is : Answer: 4. N Key idea: For isoelectronic ions (all 10 electrons), the one with the lowest nuclear charge is the largest. The ions are Na^+ (... 1
- Which one of the following statements is correct? Answer: 2. The daily requirement of Mg and Ca in the human body is estimated to be 0.2 - 0.3 g. Key idea: Recall the biological roles of Mg... 1
- Which of the following statements are NOT correct?A. Hydrogen is used to reduce heavy metal oxides to metals.B. Heavy water is used to study reaction mechanism.C. Hydrogen is used to make saturated fats from oils.D. The H-H bond dissociation enthalpy… Answer: 4. D, E only Key idea: Check each statement. A. True: H₂ reduces oxides of less active (heavy) metals. B. True: D₂O is used as a tra... 1
- Identify the incorrect statement from the following Answer: 3. The oxidation number of K in KO₂ is +4 . Key idea: in superoxide KO₂ , oxygen is O₂^- , so K is +1. Alkali metals always show +1.... 1
- Match List - I with List - II.List - I: (a) Li (b) Na (c) KOH (d) CsList - II: (i) absorbent for carbon dioxide (ii) electrochemical cells (iii) coolant in fast breeder reactors (iv) photoelectric cellChoose the correct answer from the options given… Answer: 1. (a) - (ii), (b) - (iii), (c) - (i), (d) - (iv) Key idea: recall the uses of alkali metals and their compounds. Li: electrochemica... 1
- The IUPAC name of an element with atomic number 119 is Answer: 2. ununennium Key idea: IUPAC temporary names use numerical roots: 0 = nil, 1 = un, 9 = enn, ending in -ium. Z = 119 means digits 1,... 1
- From the following pairs of ions which one is not an iso-electronic pair ? Answer: 4. Fe²⁺, Mn²⁺ Key idea: iso-electronic species have the same number of electrons. mathrmO²⁻ (10) and F^- (10): yes Na^+ (10) and mat... 1
- In which one of the following arrangements the given sequence is not strictly according to the properties indicated against it ? Answer: 2. H₂O < H₂S < H₂Se < H₂Te : Increasing pK_a values Key idea: check each trend. 1: acidic strength HF < HCl < HBr < HI is correct (w... 1
- Statement I : Acid strength increases in the order given as HF << HCl << HBr << HI.Statement II : As the size of the elements F, Cl, Br, I increases down the group, the bond strength of HF, HCl, HBr and HI decreases and so the acid strength increases… Answer: 1. Both Statement I and Statement II are true. Key idea: acid strength of hydrogen halides depends on the H-X bond strength. Down th... 1
- Match the following :Oxide | Nature(a) CO (i) Basic(b) BaO (ii) Neutral(c) Al_2O_3 (iii) Acidic(d) Cl_2O_7 (iv) AmphotericWhich of the following is correct option ? Answer: 2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii) CO: neutral oxide (a)-(ii). BaO: basic oxide of an s-block metal (b)-(i). Al₂O₃ : amphoter... 1
- The following metal ion activates many enzymes, participates in the oxidation of glucose to produce ATP and with Na, is responsible for the transmission of nerve signals. Answer: 4. Potassium Potassium ions activate many enzymes, take part in oxidation of glucose to give ATP, and together with sodium ions carr... 1
- Identify the incorrect match.Name | IUPAC Official Name(a) Unnilunium | (i) Mendelevium(b) Unniltrium | (ii) Lawrencium(c) Unnilhexium | (iii) Seaborgium(d) Unununnium | (iv) Darmstadtium Answer: 4. (d), (iv) IUPAC temporary names come from the atomic number: un=1, nil=0, tri=3, hex=6. Unnilunium = 101 = Mendelevium. Match (a)... 1
- Which of the following is an amphoteric hydroxide ? Answer: 4. Be(OH) ₂ Going down group 2, hydroxides become more basic. Sr(OH)₂ , Ca(OH)₂ and Mg(OH)₂ are basic. Be(OH)₂ dissolves in both aci... 1
- The method used to remove temporary hardness of water is : Answer: 2. Clark's method Key idea: temporary hardness is due to bicarbonates of Ca and Mg, and the method meant specifically for it is Clar... 1
- For the second period elements the correct increasing order of first ionisation enthalpy is : Answer: 2. Li < B < Be < C < O < N < F < Ne First ionisation enthalpy generally increases across a period, with two exceptions in period 2.... 1
- Enzymes that utilize ATP in phosphate transfer require an alkaline earth metal (M) as the cofactor. M is : Answer: 2. Mg ATP-utilising enzymes (phosphate transfer) need mathrmMg²⁺ as cofactor; Mg binds the phosphate groups of ATP. Ca is mainly inv... 1
- The correct order of atomic radii in group 13 elements is Answer: 4. B < Ga < Al < In < Tl Atomic radius generally increases down a group, but Ga is smaller than Al. Gallium follows the d-block (3d)... 1
- Which of the following oxides is most acidic in nature ? Answer: 3. BeO Acidic character of oxides falls as the metallic character of the element rises. In group 2, MgO, CaO and BaO are basic (basi... 1
- The element Z = 114 has been discovered recently. It will belong to which of the following family/group and electronic configuration ? Answer: 1. Carbon family, [Rn] 5f¹⁴6d¹⁰7s²7p² Key idea: element 114 lies in the same group as Pb (Z = 82), one period lower, so its outer sh... 1
- The suspension of slaked lime in water is known as Answer: 2. milk of lime Key idea: Ca(OH)₂ is only sparingly soluble in water. A suspension of slaked lime in water looks milky, so it is cal... 1