Gadolinium has a low value of third ionisation enthalpy because of
Gadolinium has a low value of third ionisation enthalpy because of
- small size
- high exchange enthalpy
- high electronegativity
- high basic character
The Correct Option is B
Solution and Explanation
The third ionization enthalpy refers to the energy required to remove an electron from a doubly positively charged ion. In the case of gadolinium (Gd), this process is influenced by several factors. The correct reason for gadolinium having a low third ionization enthalpy is its high exchange enthalpy. This is because:
1. Electron Configuration: Gadolinium's electron configuration is [Xe] 4f7 5d1 6s2. Removing electrons involves disrupting a stable half-filled f-orbital.
2. Exchange Enthalpy: The 4f orbitals in gadolinium are half-filled, which offers stability due to the exchange energy. Exchange energy results from the half-filled or fully filled subshell, leading to stability due to parallel spins allowing for maximum exchange interactions among electrons.
3. Energetic Favorability: To maintain this stable state upon ionization requires less energy compared to disrupting a configuration that does not support exchange stabilization.
Based on the factors above, the low third ionization enthalpy in gadolinium can be attributed to the high exchange enthalpy provided by the half-filled 4f orbital.
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Concepts Used:
Modern Periodic Table
Modern Periodic Table is the tabular arrangement of the elements in increasing order of their atomic numbers. It is commonly referred to as the Long Form of the Periodic Table and is based on the modern periodic law and is the tabular arrangement of elements in increasing order of their atomic numbers (Z).
*Numbering system adopted by the International Union of Pure and Applied Chemistry (IUPAC).
- The elements in the same group of the Modern Periodic Table have the same valence electron configuration and thus have similar chemical properties.
- The elements in the same period of the Modern Periodic Table will have an increasing order of valence electrons. Hence, the number of energy sub-levels per energy level increases as the energy level of the atom increases.
The periodic table of elements is as follows:
| Atomic number (Z) | Symbol | Name |
| 1 | H | Hydrogen |
| 2 | He | Helium |
| 3 | Li | Lithium |
| 4 | Be | Beryllium |
| 5 | B | Boron |
| 6 | C | Carbon |
| 7 | N | Nitrogen |
| 8 | O | Oxygen |
| 9 | F | Fluorine |
| 10 | Ne | Neon |
| 11 | Na | Sodium |
| 12 | Mg | Magnesium |
| 13 | Al | Aluminium |
| 14 | Si | Silicon |
| 15 | P | Phosphorus |
| 16 | S | Sulfur |
| 17 | Cl | Chlorine |
| 18 | Ar | Argon |
| 19 | K | Potassium |
| 20 | Ca | Calcium |
| 21 | Sc | Scandium |
| 22 | Ti | Titanium |
| 23 | V | Vanadium |
| 24 | Cr | Chromium |
| 25 | Mn | Manganese |
| 26 | Fe | Iron |
| 27 | Co | Cobalt |
| 28 | Ni | Nickel |
| 29 | Cu | Copper |
| 30 | Zn | Zinc |
| 31 | Ga | Gallium |
| 32 | Ge | Germanium |
| 33 | As | Arsenic |
| 34 | Se | Selenium |
| 35 | Br | Bromine |
| 36 | Kr | Krypton |
| 37 | Rb | Rubidium |
| 38 | Sr | Strontium |
| 39 | Y | Yttrium |
| 40 | Zr | Zirconium |
| 41 | Nb | Niobium |
| 42 | Mo | Molybdenum |
| 43 | Tc | Technetium |
| 44 | Ru | Ruthenium |
| 45 | Rh | Rhodium |
| 46 | Pd | Palladium |
| 47 | Ag | Silver |
| 48 | Cd | Cadmium |
| 49 | In | Indium |
| 50 | Sn | Tin |
| 51 | Sb | Antimony |
| 52 | Te | Tellurium |
| 53 | I | Iodine |
| 54 | Xe | Xenon |
| 55 | Cs | Caesium |
| 56 | Ba | Barium |
| 57 | La | Lanthanum |
| 58 | Ce | Cerium |
| 59 | Pr | Praseodymium |
| 60 | Nd | Neodymium |
| 61 | Pm | Promethium |
| 62 | Sm | Samarium |
| 63 | Eu | Europium |
| 64 | Gd | Gadolinium |
| 65 | Tb | Terbium |
| 66 | Dy | Dysprosium |
| 67 | Ho | Holmium |
| 68 | Er | Erbium |
| 69 | Tm | Thulium |
| 70 | Yb | Ytterbium |
| 71 | Lu | Lutetium |
| 72 | Hf | Hafnium |
| 73 | Ta | Tantalum |
| 74 | W | Tungsten |
| 75 | Re | Rhenium |
| 76 | Os | Osmium |
| 77 | Ir | Iridium |
| 78 | Pt | Platinum |
| 79 | Au | Gold |
| 80 | Hg | Mercury |
| 81 | Tl | Thallium |
| 82 | Pb | Lead |
| 83 | Bi | Bismuth |
| 84 | Po | Polonium |
| 85 | At | Astatine |
| 86 | Rn | Radon |
| 87 | Fr | Francium |
| 88 | Ra | Radium |
| 89 | Ac | Actinium |
| 90 | Th | Thorium |
| 91 | Pa | Protactinium |
| 92 | U | Uranium |
| 93 | Np | Neptunium |
| 94 | Pu | Plutonium |
| 95 | Am | Americium |
| 96 | Cm | Curium |
| 97 | Bk | Berkelium |
| 98 | Cf | Californium |
| 99 | Es | Einsteinium |
| 100 | Fm | Fermium |
| 101 | Md | Mendelevium |
| 102 | No | Nobelium |
| 103 | Lr | Lawrencium |
| 104 | Rf | Rutherfordium |
| 105 | Db | Dubnium |
| 106 | Sg | Seaborgium |
| 107 | Bh | Bohrium |
| 108 | Hs | Hassium |
| 109 | Mt | Meitnerium |
| 110 | Ds | Darmstadtium |
| 111 | Rg | Roentgenium |
| 112 | Cn | Copernicium |
| 113 | Nh | Nihonium |
| 114 | Fl | Flerovium |
| 115 | Mc | Moscovium |
| 116 | Lv | Livermorium |
| 117 | Ts | Tennessine |
| 118 | Og | Oganesson |
Read More: Periodic Classification of Elements