[AL Chem] Atomic radius
each additional electron goes to same shell and is at approxomately the same distance from the nucleur, the replusion between electrons is relatively ineffective to cause an increases in atomic radius.我唔明ar [] 唔需要明, 背左佢啦[] 本帖最後由 Hinton 於 26-8-2009 11:49 編輯
其實呢兩句說話表達既野
應該係關screening(shield) effect既事
點解題目有講relatively?
咁當然有對比啦
其實佢呢個repulsion between electrons
係同個attraction between nucleus and electrons作比較
如果個screening effect compares with effective nucleus charge
個screening係相對黎講 影響比較少
總結黎講
上面個兩句
提出atomic radius受兩個factors所影響
(1) screening effect(repulsion between electrons)
(2) effective nucleus charge
而(1)--->atomic radius增加
因為個排斥足以令 個d outermost shell electrons同個nucleus既distance increases
但(2)--->atomic radius減少
因為個吸引力 會令個d outermost shell electrons同個nucleus 既distance decreases
由於一個增加 一個減少
所以有必要比較兩者既影響
screening effect<<effective nucleus charge
所以當兩種因素並存既時候 我地會強調個atomic radius會減少左
3#
For the same period, the two factors should be shielding effect and nuclear charge.
The combined factor is effective nuclear charge.
提出atomic radius受兩個factors所影響
(1) screening effect(repulsion between electrons)
(2) effective nucleus charge
Hinton 發表於 26/8/2009 03:34 AM http://nakuz.com/bbs/images/common/back.gif
唔係wow
我聽人講
effective nuclear charge=nuclear charge減screening effect 本帖最後由 【YU】 於 30-11-2009 18:35 編輯
LK 身痕到摷返晒d陳年舊物出黎串咀.
For the same period, no. of inner electrons are the same, shielding effect is constant.
ENC = NC - sheiding
Magnitude of ENC and NC moves in the same direction by the same amount, both are OK for consideration. But to be more accurate, better use ENC to repesent the net attraction.
Atomic size = ENC(attraction by nucleus) vs screening(repulsion between electrons in the same shell) ENC = the charges of the nucleus - the total charges of inner shells electrons
e.g.
enc of fluorine=+7(+9 - 2)
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