Hydrides — Ionic, covalent, metallic
Hydrogen
4
JEE Qs
8%
Hard
75
min
Master the classification, properties, and characteristic reactions of each hydride type, paying special attention to exceptions and trends across the periodic table.
🧮 Key Formulas
✅ Key Points for JEE
- 1Ionic (Saline) Hydrides are formed by s-block elements (Group 1 and heavier Group 2 metals). They are non-volatile crystalline solids, strong reducing agents, and produce H2 gas at the anode when molten or in solution due to H- ions.
- 2Covalent (Molecular) Hydrides are formed by p-block elements. They are volatile compounds with distinct molecular properties and are classified as electron-deficient (Group 13, e.g., B2H6), electron-precise (Group 14, e.g., CH4), and electron-rich (Group 15-17, e.g., NH3, H2O, HF – due to lone pairs, capable of hydrogen bonding).
- 3Metallic (Interstitial) Hydrides are formed by most d-block and f-block elements, typically non-stoichiometric (except CrH). They retain metallic properties like conductivity and luster, and their ability to absorb large volumes of hydrogen makes them useful for hydrogen storage.
- 4BeH2 and MgH2 exhibit significant covalent character, departing from the typical ionic nature of other Group 2 hydrides. The 'hydride gap' refers to the absence of hydrides for Group 7, 8, and 9 elements.
- 5The reducing strength of ionic hydrides increases down the group. The acidic strength of covalent hydrides increases across a period and down a group, while basic strength typically decreases across a period.
⚠️ Common Mistakes
- ✕Confusing the properties of different types of hydrides, especially ionic vs. covalent (e.g., conductivity, state at room temperature, reaction with water).
- ✕Forgetting the 'hydride gap' (Group 7, 8, 9 elements do not form hydrides) or specific exceptions like the covalent nature of BeH2 and MgH2.
- ✕Incorrectly predicting the products or behavior of hydrides in reactions, particularly the production of H2 gas at the anode for ionic hydrides during electrolysis, or their violent reaction with water.
📝 Practice Questions
See allQ34.Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Loss of electron from hydrogen atom results in nucleus of ~1 . 5 × 10 – 3 pm size. Reason R: Proton H+ always exists in combined form. In the light of the above statements, choose the most appropriate answer from the options given below: (1) Both A and R are correct and R is the correct (2) A is correct but R is not correct explanation of A (3) A is not correct but R is correct (4) Both A and R are correct but R is NOT the correct explanation of A
Q41.Which of the following can reduce decomposition of H2O2 on exposure to light (1) Urea (2) Alkali (3) Glass containers (4) Dust
Q31.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: Hydrogen is an environment friendly fuel. Reason R: Atomic number of hydrogen is 1 and it is a very light element. In the light of the above statements, choose the correct answer from the options given below (1) A is true but R is false (2) Both A and R are true but R is NOT the correct explanation of A (3) A is false but R is true (4) Both A and R are true and R is the correct explanation of A
Q39.Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Gypsum is used for making fireproof wall boards. Reason (R): Gypsum is unstable at high temperatures. In the light of the above statements, choose the correct answer from the options given below: (1) Both (A) and (R) are correct but (R) is not the (2) (A) is correct but (R) is not correct. correct explanation of (A). (3) (A) is not correct but (R) is correct. (4) Both (A) and (R) are correct and (R) is the correct explanation of (A).
Q47.The water gas on reacting with cobalt as a catalyst forms (1) Methanal (2) Methanoic acid (3) Ethanol (4) Methanol
Q36.Given below are two reactions, involved in the commercial production of dihydrogen H2. The two reactions are carried out at temperature “T1” and “T2”, respectively T1 Cs + H2Og ⟶COg + H2g T2 COg + H2Og CatalystCO2g + H2g The temperatures T1 and T2 are correctly related as (1) T1 = T2 (2) T1 < T2 (3) T1 = 100 K, T2 = 1270 K (4) T1 > T2
NCERT Chapters
- Class 11 Chemistry Ch 9: Hydrogen