為什麼金的純金度不能達100%?

because~純金 - 即24K或999.9，純度愈高的金飾愈軟則越容易變形。
根據中央標準局民國79年公佈的
飾金金屬標示及成份的國家標準
所謂「純金」係金含量為99.5%以上
成份符號則以24K標示
所以黃金中「K」是代表金含量的比例

黃金(Au)：
是一種黃色貴金屬。製造首飾珠寶，可用純金(即24K或999.9黃金)或不同純金度的合金( 又稱「K金」)。最普遍的是18K金 ( 含75%純金 )及14K金 ( 含58.5%純金 )。
質地柔軟富延展性，可以煉成各種形狀；但也因為它不易成形，所以鑲嵌鑽石或寶石的珠寶多半一定用合金 ( 又稱「K金」) 。合金較黃金堅硬，能做多種造形設計；並且，Ｋ金的顏色比較富變化性：黃Ｋ金、粉紅金、綠色金、白色金、藍色金……等，色彩真是多采多姿！只是，這幾年比較流行白Ｋ金；黃Ｋ金，只得尋找慧眼獨具之士了。

kopo1128 answer is right!!!
因為問題是金,而不飾金!!

當然,如果kncym4想問“為什麼‘飾金’的純金度不能達100%?”
cherrychang151的答案是可以接受的

純度愈高的金飾愈軟則越容易變形？請問為什麼？

it is because the gold is too soft so we need to add so thing the fixed the shape

如果純金度達100%金身就會很軟,若果不加一些化學物質,金不可以變成堅硬,至於1%便就是其他化學物,加上99%純金,便生成我們平時所見的硬金。

The pure gold cannot be expressed as 100% because no one can garantee whether the pure gold is 100% pure. In principle, no matter how tiny the contamination is, it can still not be described as 100% pure. This is also the reason why nobody will claim they can produce something 100% pure. But they can only garantee whether the purity can up to certain level. The same principle is applied in many other chemicals and elements.

By the normal refining method, the purity of gold of 99.99% can easily be achieved. So, many of the gold from jewelry shop claimed to be 99.99%. However, practically, it is seldom the case since most of the 24K gold may contain solder which contains less gold content. It ends up a lower gold content in the jewelry item.

In fact, the purity of gold can sometimes be up to 99.999% or even higher. It just depends on the method you use for refining and how good the care you give during the refining process. However, no matter what, nobody will claim they can produce 100% pure gold since it does not make sense at all.

I hope the information can help.

因為黃金太軟...因此 金屬like銀, 鉑, 銅 , 鎳,鈀

因為 黃金 100% 係軟

為左做成硬身 所以會加入 少少 雜質 咁就會變硬

係咩雜質 我唔記得左

所以芾面上既金 係 999.9 0.1 係 雜質

黃金純度100%的話，黃金會太軟，令金飾不能達至理想型態。

但現在的科學，已經能把黃金的純度提升至99.99%

因為黃金太軟...硬度不足....因此 如果不加入 化學物質 或 金屬 是不能夠做出各種想達到的型態...for example 戒指.. 而99% 是指 黃金的純金度 .... 而 1 % 大概係化學物質...