Kossel-Lewis approach, ionic and covalent bonds
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See all →- Amongst the following, the total number of species NOT having eight electrons around central atom in its outer most shell, isNH_3, AlCl_3, BeCl_2, CCl_4, PCl_5 : Answer: 2. 3 Key idea: Count the electrons in the valence shell of the central atom. NH₃ : 8 (3 bond pairs + 1 lone pair). AlCl₃ : 6 (incomp... 1
- Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is 1s^2 2s^2 2p^3, the simplest formula for this compound is Answer: 4. Mg ₃ X ₂ X has configuration 1s²2s²2p³ , so it is nitrogen and forms mathrmX³⁻ . Magnesium forms mathrmMg²⁺ . Balancing charges:... 1
- Iron exhibits bcc structure at room temperature. Above 900°C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900°C (assuming molar mass and atomic radii of iron remains constant with temperature) is Answer: 2. 3√(3)/4√(2) Density =Z M/a³ N_A . Since M and atomic radius r are the same, compare Z/a³ . bcc: Z=2 , a=4r/sqrt3 . fcc: Z=4 , a=2... 1