Խայտառակ տականքություն․․

Խայտառակ տականքություն Նիկոլի դեմ. Այլանդակ քայլ Ռուսաստանից

Քոմենթում ՊԼՅՈՒՍ դրեք,եթե Նիկոլի կողքին եք մինչև վերջ❗️❗️

Խայտառակ տականքություն Նիկոլի դեմ. Այլանդակ քայլ Ռուսաստանից

Քոմենթում ՊԼՅՈՒՍ դրեք,եթե Նիկոլի կողքին եք մինչև վերջ❗️❗️

Խայտառակ տականքություն Նիկոլի դեմ. Այլանդակ քայլ Ռուսաստանից

Քոմենթում ՊԼՅՈՒՍ դրեք,եթե Նիկոլի կողքին եք մինչև վերջ❗️❗️

 

 

 

 

 

 

 

The electrons in the 4f-subshell, which is progressively filled across the lanthanide series, are not particularly effective at shielding the increasing nuclear charge from the sub-shells further out. The elements immediately following the lanthanides have atomic radii that are smaller than would be expected and that are almost identical to the atomic radii of the elements immediately above them.[38] Hence hafnium has virtually the same atomic radius (and chemistry) as zirconium, and tantalum has an atomic radius similar to niobium, and so forth. This is known as the lanthanide contraction. The effect of the lanthanide contraction is noticeable up to platinum (element 78), after which it is masked by a relativistic effect known as the inert pair effect.[39] The d-block contraction, which is a similar effect between the d-block and p-block, is less pronounced than the lanthanide contraction but arises from a similar cause.[38]

Ionization energy

Ionization energy: each period begins at a minimum for the alkali metals, and ends at a maximum for the noble gases
Main article: Ionization energy
The first ionization energy is the energy it takes to remove one electron from an atom, the second ionization energy is the energy it takes to remove a second electron from the atom, and so on. For a given atom, successive ionization energies increase with the degree of ionization. For magnesium as an example, the first ionization energy is 738 kJ/mol and the second is 1450 kJ/mol. Electrons in the closer orbitals experience greater forces of electrostatic attraction; thus, their removal requires increasingly more energy. Ionization energy becomes greater up and to the right of the periodic table.[39]

Large jumps in the successive molar ionization energies occur when removing an electron from a noble gas (complete electron shell) configuration. For magnesium again, the first two molar ionization energies of magnesium given above correspond to removing the two 3s electrons, and the third ionization energy is a much larger 7730 kJ/mol, for the removal of a 2p electron from the very stable neon-like configuration of Mg2+. Similar jumps occur in the ionization energies of other third-row atoms.[39]

Electronegativity
Main article: Electronegativity

Graph showing increasing electronegativity with growing number of selected groups
Electronegativity is the tendency of an atom to attract a shared pair of electrons.[40] An atom’s electronegativity is affected by both its atomic number and the distance between the valence electrons and the nucleus. The higher its electronegativity, the more an element attracts electrons. It was first proposed by Linus Pauling in 1932.[41] In general, electronegativity increases on passing from left to right along a period, and decreases on descending a group. Hence, fluorine is the most electronegative of the elements,[n 5] while caesium is the least, at least of those elements for which substantial data is available.[23]

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