تصویر جدول تناوبی و آرایش اربیتالی

To understand what this means in terms of an element's electron configuration, let's consider the Group 1A metals. If we write the electron configuration for the Group 1A metal from each row of the Periodic Table, we have:

row 2	Li:	$1 s 22 s 1$
row 3	Na:	$1 s 22 s 22 p 63 s 1$
row 4	K:	$1 s 22 s 22 p 63 s 23 p 64 s 1$
row 5	Rb:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 1$
row 6	Cs:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 1$
row 7	Fr:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 24 f 145 d 106 p 67 s 1$

Do you see any pattern? For Group 1A metals, it seems that element's row corresponds to the energy level of that element's valence electron. Lithium (Li), for instance, is found in row 2 of the Periodic Table, and its valence electron is found in the n = 2 energy level. Cesium (Cs) is found in row 6 of the Periodic Table, and its valence electron is found in the n = 6 energy level. Let's see if this same pattern holds for Group 2A metals:

row 2	Be:	$1 s 22 s 2$
row 3	Mg:	$1 s 22 s 22 p 63 s 2$
row 4	Ca:	$1 s 22 s 22 p 63 s 23 p 64 s 2$
row 5	Sr:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 2$
row 6	Ba:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 2$
row 7	Ra:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 24 f 145 d 106 p 67 s 2$

For Group 2A metals, the same rule applies! Magnesium (Mg) is found in row 3 of the Periodic Table, and its valence electrons are found in the n = 3 energy level. Similarly, Radium (Ra) is found in row 7 of the Periodic Table, and its valence electrons are found in the n = 7 energy level.

So far so good – but does the same pattern apply to the Group 3A–8A elements (also known as Groups 13–18). Let's find out by writing the electron configuration for the Group 3A element in each row.

row 2	B:	$1 s 22 s 22 p 1$
row 3	Al:	$1 s 22 s 22 p 63 s 23 p 1$
row 4	Ga:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 1$
row 5	In:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 1$
row 6	Tl:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 25 d 106 p 1$

Even though the valence electrons in Group 3A elements are found in both s and p orbitals, it turns out that an element's row still corresponds to the energy level of that element's valence electrons. For example, Gallium (Ga) is found in row 4 of the Periodic Table, and its valence electrons are found in the n = 4 energy level. Likewise, Thallium (Tl) is found in row 6 of the Periodic Table, and its valence electrons are found in the n = 6 energy level.

It really does seem as if we can predict the energy level of an element's valence electrons using the row number for that element in the Periodic Table. Let's try one last example, though, just to be sure by writing the electron configuration for the Group 7A element in each row.

row 2	F:	$1 s 22 s 22 p 5$
row 3	Cl:	$1 s 22 s 22 p 63 s 23 p 5$
row 4	Br:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 5$
row 5	I:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 5$
row 6	At:	$1 s 22 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 25 d 106 p 5$

+ نوشته شده در یکشنبه ۲۸ اسفند ۱۳۹۰ ساعت 8:41 توسط مجید انتشاری(مدیر پایگاه) |

پايگاه اطلاع ‏رساني شيمي

مطالبی ناب درباره دروس تخصصی شیمی کلیه گرایشها

تصویر جدول تناوبی و آرایش اربیتالی

نوشته‌های پیشین

آرشیو موضوعی

نویسندگان

پیوندها