Home
Class 12
CHEMISTRY
Why the melting points of NaF and MgO (9...

Why the melting points of `NaF` and `MgO` `(990^(@)C` and `2640^(@)C`) are so different although both have same number of electrons and nearly the same internuclear distance (236 pm and 216 pm)?

Text Solution

AI Generated Solution

To understand why the melting points of sodium fluoride (NaF) and magnesium oxide (MgO) are so different, we need to analyze the nature of the ionic bonds in these compounds. ### Step-by-Step Solution: 1. **Identify the Compounds**: - Sodium fluoride (NaF) is composed of sodium ions (Na⁺) and fluoride ions (F⁻). - Magnesium oxide (MgO) consists of magnesium ions (Mg²⁺) and oxide ions (O²⁻). ...
Promotional Banner

Topper's Solved these Questions

  • NCERT BASED EXERCISE

    CENGAGE CHEMISTRY ENGLISH|Exercise NCERT Exercise|104 Videos

  • NCERT BASED EXERCISE

    CENGAGE CHEMISTRY ENGLISH|Exercise Short Answer Type Questions(ElectroCHMmical Cell)|4 Videos

  • NCERT BASED EXERCISE

    CENGAGE CHEMISTRY ENGLISH|Exercise NCERT Exerise|25 Videos

  • GRIGNARD REAGENTS AND ORGANOMETALLIC REAGENTS

    CENGAGE CHEMISTRY ENGLISH|Exercise Exercises Archives (Linked Comprehension)|1 Videos

  • NUCLEAR CHEMISTRY

    CENGAGE CHEMISTRY ENGLISH|Exercise Archives Subjective|13 Videos

Similar Questions

Explore conceptually related problems

The ions of NaF and MgO have the same number of electrons and inter nuclear distances are about the same (235 pm and 215 pm). Why are then the melting points of NaF and MgO so different (992^(@)C and 2642^(@)C) ?

Observe the following statements regarding isotones : a. .^(39)K and .^(40)Ca are isotones. b. Nucleides having different atomic number (Z) and mass numbers (a) but same number of neutrons (n) are called isotones. c. .^(19)F and .^(23)Na are isotones. The correct answer is -

The half-life period of a radioactive element x is same as the mean life time of another radioactive element y. Initially, both of them have the same number of atoms. Then, (a) x and y have the same decay rate initially (b) x and y decay at the same rate always (c) y will decay at a faster rate than x (d) x will decay at a faster rate than y

Why does moon have very cold and very hot temperature variations e.g., from -190^(@)C to 110^(@)C even though it is at the same distance from the sun as the earth is?

It is not possible to measure the atomic radius prectsely since the electron cloub surrouding the atom does not have a sharp boundary. One practial approach to estimate the size of an atom of a non-metallic element is to measure the distance between two atoms when they are bound togther by a signle bond in a covalent molecule and then dividing by two. For metals we define the term "matellic radius" which is taken as half the internuclear distance separating the metal cores in the metallic crystal. Then van der waal's radius represents the over all size of the atoms which includes its valence shell in a non bonded situation. It is the half of the distance between two similar atoms in separate molecules in a solid. The atomis radius decreases across a period and increases down the group. Same trends are observed in case of ionic radius. Ionic radius of the species having same number of electrons depends on the number of protons in their nuclei. Sometimes, atomic and ionic radii give unexpected trends due to poor shielding of nuclear charge by d -and f- orbital electrons. Now answer the following three questions: Select the INCORRECT option regarding atomic//ionic sizes:

The sharp melting point of crystalline solids compared to amorphous solids is due to a) a regular arrangement of constituent particles observed over a short distance in the crystal lattice. b) a regular arrangement of constituent particles observed over a long distance in the crystal lattice. c) Same arrangement of constituent particles in different directions. d) Different arrangement of constituent particles in different directions.

The compound unstabel nucleus ._(92)^(236)U often decays in accordance with the following reaction ._(92)^(236)U rarr ._(54)^(140)Xe +._(38)^(94)Sr + other particles During the reaction, the uranium nucleus ''fissions'' (splits) into the two smaller nuceli have higher nuclear binding energy per nucleon (although the lighter nuclei have lower total nuclear binding energies, because they contain fewer nucleons). Inside a nucleus, the nucleons (protonsa and neutrons)attract each other with a ''strong nuclear'' force. All neutrons exert approxiamtely the same strong nuclear force on each other. This force holds the nuclear are very close together at intranuclear distances. A proton and a neutron are both shot at 100 m s^(-1) toward a ._6^(12)C nucleus. Which particle, if either, is more likely to be absorbed by the nucleus?

(a) How is the valency of an element determined if its electronic configuration is known? Determine the valency of an element of atomic no. 9 (b) Given below are some elements of the Modern Periodic Table. Atomic numbers of the elements are given in the parentheses: A(4), B(9), C(14), D(19), E(20) (i) With the help of the electronic configuration, find out which one of the above elements will have one electron in its outermost shell? (ii) Which rwo elements belong to the same group? Give reasons for your answer. (iii) Which one of the above elements belonging to the fourth period has bigger atomic radius and why?.

An electric field is defined in terms of q_(0) a small positive charge. If the definition was in terms of a small negative charge of the same magnitude, then compared to the original field the newly defined electric field. (a) would point in the same direction and have the same magnitude. (b) would point in the opposite direction and have the same magnitude. (c ) would point in the same direction and have the different magnitude. (d) would point in the opposite direction and have the different magnitude.

Answer the following: (i) If two similar large plates, each of area A having surface charge densities +sigma and -sigma are separated by a distance d in air,find the expression for (a) field at points between the two plates and on outer side of the plates. Specify the direction of the field in each case. (b) the potential difference between the plates. (c) the capacitance of the capacitor so formed. (ii) Two metallic spheres of radii R and 2R are charged so that both of these have same surface charge density sigma . If they are connected to each other with a conducting wire, in which direction will the charge flow and why ?

CENGAGE CHEMISTRY ENGLISH-NCERT BASED EXERCISE-Short Answer Type Questions
  1. Why do some substance exist as solids?

    Text Solution

    |

  2. Why do the window glass of old old building (a) look milky and (b) bec...

    Text Solution

    |

  3. Why the melting points of NaF and MgO (990^(@)C and 2640^(@)C) are so ...

    Text Solution

    |

  4. How many types of centred unit cells exist?

    Text Solution

    |

  5. How many types of two-dimensional lattice exist? Why pentagonal lattic...

    Text Solution

    |

  6. How many TVs and OV s occur per unit cell and per atom in a closest pa...

    Text Solution

    |

  7. Where the TVs and OV s are located in a closet packed structure?

    Text Solution

    |

  8. What is the distance between two TVs?

    Text Solution

    |

  9. In an hcp structure, calculate Z("eff)

    Text Solution

    |

  10. In a diamond cubic (dc) structure, calculate Z("eff")

    Text Solution

    |

  11. What is the ratio of (TV//OV)("occupied") in spinel an inverse spinel...

    Text Solution

    |

  12. What is the CN of cation and anion in a corundum structure?

    Text Solution

    |

  13. What is the occurrence of different forms of the same compound called?

    Text Solution

    |

  14. How many allotropic forms of Carbon exist?

    Text Solution

    |

  15. How can a substance be made amorphous?

    Text Solution

    |

  16. Why does ZnO show increased electrical conductivity and turns yellow o...

    Text Solution

    |

  17. Why NiO and FeO are nonstroichiometric with the formula Ni(0.98)O and ...

    Text Solution

    |

  18. Why the defectsof the crystalline solids are called thermodynamic defe...

    Text Solution

    |

  19. Why stoichiometric defects are also called intrinsic defects?

    Text Solution

    |

  20. Give the name of one solid which shows both Schottky and Frenkel defec...

    Text Solution

    |