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07th Mar 2020 @ 3 min read
The Newlands law of octaves states that when elements are arranged in the increasing order of atomic weights, every eighth element has similar properties to the first. In other words, the properties of elements are repeated after every seventh interval.
Newlands arranged 56 elements (hydrogen to thorium) known at that time in the increasing order of atomic weights. He observed the periodicity in the arrangement.
The table below is from Newlands' publication of 1865. He ordered the elements from the top to bottom in the increasing order of atomic weights. The numbers in the table are not atomic weights but ordering numbers.
|Order No.||Element||Order No.||Element||Order No.||Element||Order No.||Element||Order No.||Element||Order No.||Element||Order No.||Element||Order No.||Element|
|1||H||8||F||15||Cl||22||Co & Ni||29||Br||36||Pd||42||I||50||Pt & Ir|
|3||Be||10||Mg||17||Ca||24||Zn||31||Sr||38||Cd||45||Ba & V||52||Hg|
|4||B||11||Al||19||Cr||25||Y||33||Ce & La||40||U||46||Ta||53||Tl|
|6||N||13||P||20||Mn||27||As||34||Nd & Mo||41||Sb||48||Nb||55||Bi|
|7||O||14||S||21||Fe||28||Se||35||Ro & Ru||43||Te||49||Au||56||Th|
According to the law of octaves, every eighth element in the above table must share similar physical and chemical properties. Thus, each element in the same row must have similar physical and chemical properties. But this is not true. The periodicity is only valid till calcium. An example of this is lithium, sodium, and potassium; they share physical and chemical properties. The remaining elements after potassium, (Cu, Rb, Ag…) are different and do not show similarities to the former elements. This is because the law of octaves fails to incorporate transition metals.
In the previous table, several elements are missing, particularly the noble gases—He, Ne, Ar, Kr, Xe, and Rn. The reason is they were not discovered. Also, the ordering becomes inconsistent after calcium, for example, the position of Ti and Cr is interchanged. Some elements were placed in the same position (Co & Ni, Ce & La, Nd & Mo…). The other thing to notice is that elements are ordered from top to bottom which is the transpose of the modern periodic table where the ordering is from the left to right.
John Alexander Reina Newlands was an English chemist, born in London, England. He completed his education at the Royal College of Chemistry and worked as an analytical chemist.
In 1865, he published his periodic system and named as the law of octaves since it is analogous to octaves in music.
Although he was the first after de Chancourtois to discover the periodicity, his work was not initially recognized by scientific communities. Later on, it was acknowledged, and he received the Davy Medal in 1887 for it.
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