History of periodic table Questions in English

(D) The Modern Periodic Law states that the physical and chemical properties of elements are a periodic function of their atomic numbers. This law was proposed by $H.G.J. \, Moseley$ in $1913$ based on his experiments with $X$-ray spectra of elements. Before this,$Mendeleev$ had proposed the periodic law based on atomic mass.

(A) The telluric helix,also known as the $vis \text{ } tellurique$,was a three-dimensional arrangement of elements proposed by the French geologist $A.E. \text{ } B. \text{ } de \text{ } Chancourtois$ in $1862$.
He arranged the elements in order of increasing atomic weights along a helix on the surface of a cylinder.

(A) Mendeleev's periodic law states that the physical and chemical properties of elements are a periodic function of their atomic weights.

(C) According to Dobereiner's law of triads,the atomic mass of the central element is approximately the arithmetic mean of the atomic masses of the other two elements in the triad.
For the triad $Cl, Br, I$:
Atomic mass of $Cl = 35.5$
Atomic mass of $I = 127$
Arithmetic mean = $\frac{35.5 + 127}{2} = 81.25$
This value is close to the actual atomic mass of $Br$ $(80)$.
Thus,$Cl, Br, I$ forms a Dobereiner triad.

(A) The most important active step in the development of the periodic table was taken by $Mendeleev$.
Although other scientists made significant contributions toward the classification of elements,$Mendeleev$ organized the elements based on their atomic weights and periodic properties,which significantly advanced the field more than anyone else.

(D) Hydrogen shows anomalous behavior because it exhibits similarities with both alkali metals (Group $1$) and halogens (Group $17$). Due to this dual nature,its position in the periodic table is considered unique or anomalous.

(D) The development of the Periodic Table involved several scientists such as $Lothar \text{ } Meyer$ (Atomic volume curve),$Newlands$ (Law of Octaves),and $Prout$ (Prout's Hypothesis). $Rutherford$ is primarily known for his contributions to atomic structure,specifically the discovery of the atomic nucleus,and is not associated with the development of the Periodic Table.

(C) $H$. $G$. $J$. Moseley proposed the Modern Periodic Law,which states that the physical and chemical properties of elements are a periodic function of their atomic numbers $(Z)$.

(B) Moseley's work on $X$-ray spectra established that the frequency of $X$-rays emitted by an element is related to its atomic number $(Z)$ by the equation $\sqrt{\nu} = a(Z - b)$,which proved the significance of the atomic number over atomic mass.

(D) The modern periodic law states that the physical and chemical properties of elements are a periodic function of their atomic numbers.
This law was proposed by $H.G.J. Moseley$ in $1913$ based on his experiments with $X$-ray spectra of elements.
Therefore,the correct option is $D$.

(B) Lothar Meyer plotted atomic volume against atomic mass.
In this curve,the peaks are occupied by alkali metals (like $Li, Na, K, Rb, Cs$).
The descending part of the curve is occupied by alkaline earth metals (like $Be, Mg, Ca, Sr, Ba$).
The ascending part of the curve is occupied by halogens.
Therefore,the descending position next to the peak is held by alkaline earth metals.

(C) According to the Lothar Meyer curve,elements located on the descending part of the curve are Alkaline Earth Metals $(AEM)$.
Since $M$ is an Alkaline Earth Metal,its valency is $+2$.
Therefore,the nitrate of $M$ will be formed by the combination of $M^{2+}$ and $NO_3^-$.
The chemical formula is $M(NO_3)_2$.

(D) Dobereiner's law of triads states that the atomic mass of the middle element is approximately the arithmetic mean of the atomic masses of the other two elements in the triad.
For the set $(Li, Na, K)$,the atomic masses are $7, 23, 39$. The mean of $Li$ and $K$ is $(7+39)/2 = 23$,which is the atomic mass of $Na$.
For the set $(Cl, Br, I)$,the atomic masses are $35.5, 80, 127$. The mean of $Cl$ and $I$ is $(35.5+127)/2 = 81.25$,which is approximately $80$.
In the given options,none of the sets represent a valid Dobereiner's triad. Therefore,the correct option is $D$.

(C) According to Dobereiner's law of triads,the atomic mass of the middle element is approximately the arithmetic mean of the atomic masses of the other two elements in the triad.
For the triad $(Cl, Br, I)$:
Atomic mass of $Br = \frac{\text{Atomic mass of } Cl + \text{Atomic mass of } I}{2}$
Atomic mass of $Br = \frac{35.5 + 127}{2}$
Atomic mass of $Br = \frac{162.5}{2} = 81.25$

(C) Lothar Meyer plotted a graph between atomic volume and atomic mass of elements. He observed that elements with similar properties occupied similar positions on the curve. Thus,he used atomic volume as the basis for the periodic classification of elements.

(D) Lothar Meyer plotted the atomic volume against the atomic mass of elements.
He observed that elements with similar properties occupied similar positions on the curve.
Specifically,the alkali metals $(Li, Na, K, Rb, Cs)$ occupied the peaks of the curve.
These elements are highly electropositive and possess the largest atomic volumes in their respective periods.

(B) Henry Moseley,through his experiments on $X$-ray spectra of various elements,demonstrated that the frequency of $X$-rays emitted by an element is related to its atomic number $(Z)$ rather than its atomic mass.
This discovery led to the formulation of the Modern Periodic Law,which states that the physical and chemical properties of elements are a periodic function of their atomic numbers.

(A) According to the law of triads,the atomic weight of the middle element is approximately the arithmetic mean of the atomic weights of the first and third elements in the triad.
For the triad $Cl, Br, I$:
Atomic weight of $Br = \frac{\text{Atomic weight of } Cl + \text{Atomic weight of } I}{2} = \frac{35.5 + 127}{2} = 81.25 \approx 80$.

(N/A) Mendeleev arranged the elements in his periodic table ordered by atomic weight or mass. He arranged the elements in periods and groups in order of their increasing atomic weight. He placed the elements with similar properties in the same group.
However,he did not stick to this arrangement for long. He found out that if the elements were arranged strictly in order of their increasing atomic weights,then some elements did not fit within this scheme of classification.
Therefore,he ignored the order of atomic weights in some cases. For example,the atomic weight of iodine $(I)$ is lower than that of tellurium $(Te)$. Still,Mendeleev placed tellurium (in Group $VI$) before iodine (in Group $VII$) simply because iodine's properties are so similar to fluorine $(F)$,chlorine $(Cl)$,and bromine $(Br)$.

(N/A) Mendeleev's Periodic Law states that the physical and chemical properties of elements are periodic functions of their atomic weights. On the other hand,the Modern Periodic Law states that the physical and chemical properties of elements are periodic functions of their atomic numbers.

(N/A) The periodic table is arguably the most important concept in chemistry,both in principle and in practice. It serves as an everyday support for students,suggests new avenues of research to professionals,and provides a succinct organization of the whole of chemistry.
It is a remarkable demonstration of the fact that the chemical elements are not a random cluster of entities but instead display trends and lie together in families.
An awareness of the periodic table is essential to anyone who wishes to understand the world and see how it is built up from the fundamental building blocks of chemistry,the chemical elements.

(N/A) According to Glenn $T$. Seaborg,the periodic table is arguably the most important concept in chemistry,both in principle and in practice.
It serves as an everyday support for students,suggests new avenues of research to professionals,and provides a succinct organization of the whole of chemistry.
It is a remarkable demonstration of the fact that the chemical elements are not a random cluster of entities but instead display trends and lie together in families.
An awareness of the periodic table is essential to anyone who wishes to understand the world and see how it is built up from the fundamental building blocks of chemistry,the chemical elements.

(N/A) We know by now that the elements are the basic units of all types of matter. In $1800$,only $31$ elements were known. By $1865$,the number of identified elements had more than doubled to $63$. At present,$114$ elements are known. Of them,the recently discovered elements are man-made. Efforts to synthesize new elements are continuing. With such a large number of elements,it is very difficult to study the chemistry of all these elements and their innumerable compounds individually. To ease this problem,scientists searched for a systematic way to organize their knowledge by classifying the elements. This not only rationalizes known chemical facts about elements but also helps in predicting new ones for further study.

(N/A)

Scientist and Country	Year and Contribution
$1$. Johann Dobereiner (Chemist),German	$1829$. Law of Triads: He noted a similarity among the physical and chemical properties of groups of three elements (triads). The atomic weight of the middle element was approximately the average of the other two.
$2$. $A.E.B.$ de Chancourtois (Geologist),French	$1862$. Telluric Helix: He arranged known elements in order of increasing atomic weights on a cylindrical table to display the periodic recurrence of properties.
$3$. John Alexander Newlands (Chemist),English	$1865$. Law of Octaves: He arranged elements in increasing order of atomic weights and noted that every eighth element had properties similar to the first.
$4$. Dmitri Mendeleev (Chemist),Russian	$1869$. Periodic Law: "The properties of the elements are a periodic function of their atomic weights." He created the first comprehensive periodic table.
$5$. Lothar Meyer (Chemist),German	$1868$. Atomic Volume Curve: He plotted physical properties like atomic volume against atomic weight,showing a periodically repeated pattern.
$6$. Henry Moseley (Physicist),English	$1913$. Modern Periodic Law: He observed that the square root of $X$-ray frequency $(\sqrt{\nu})$ plotted against atomic number $(Z)$ gives a straight line. He stated: "The physical and chemical properties of elements are periodic functions of their atomic number."

(N/A)

Scientist	Contribution
$1$. Johann Dobereiner	Proposed the $Law \ of \ Triads$ $(1829)$,stating that the atomic weight of the middle element is approximately the average of the other two.
$2$. $A.E.B.$ de Chancourtois	Proposed the $Telluric \ Helix$ $(1862)$,a cylindrical arrangement of elements based on increasing atomic weights.
$3$. John Newlands	Proposed the $Law \ of \ Octaves$ $(1865)$,observing that every eighth element has properties similar to the first.
$4$. Dmitri Mendeleev	Formulated the $Periodic \ Law$ $(1869)$,stating that properties of elements are a periodic function of their atomic weights.
$5$. Lothar Meyer	Plotted physical properties like atomic volume against atomic weight,showing a periodic pattern $(1868)$.
$6$. Henry Moseley	Established the $Modern \ Periodic \ Law$ $(1913)$ by showing that properties are a periodic function of atomic number $(Z)$.

(N/A) The German chemist,Johann Dobereiner,was the first to consider the idea of trends among the properties of elements.
He noted a similarity among the physical and chemical properties of groups of three elements,which he called "Triads".
"Law of Triads":
- "The atomic weight of the middle element of each of the Triads was approximately the arithmetic mean of the atomic weights of the other two elements."

Triad Number	Elements and Atomic Weights	Average of $1^{st}$ and $3^{rd}$ element
$(1)$	$Li(7), Na(23), K(39)$	$(7+39) / 2 = 23$
$(2)$	$Ca(40), Sr(88), Ba(137)$	$(40+137) / 2 = 88.5$
$(3)$	$Cl(35.5), Br(80), I(127)$	$(35.5+127) / 2 = 81.25$

Conclusion: The atomic weight of the middle element is approximately equal to the average of the atomic weights of the first and third elements.

(N/A) John Alexander Newlands in $1865$ proposed the Law of Octaves.
- Law: "Every eighth element has properties similar to the first element."
- The relationship is analogous to the musical scale,where every eighth note resembles the first. For his work,he was later awarded the Davy Medal in $1887$ by the Royal Society,London.

Element	$Li, Be, B, C, N, O, F$
At. wt.	$7, 9, 11, 12, 14, 16, 19$
Element	$Na, Mg, Al, Si, P, S, Cl$
At. wt.	$23, 24, 27, 29, 31, 32, 35.5$
Element	$K, Ca$
At. wt.	$39, 40$

(N/A) John Alexander Newland in $1865$ proposed the Law of Octaves.
- Law: "Every eighth element has properties similar to the first element."
- The relationship is analogous to the musical scale where every eighth note resembles the first. For his work,he was later awarded the Davy Medal in $1887$ by the Royal Society,London.

Element	$Li$	$Be$	$B$	$C$	$N$	$O$	$F$
At. wt.	$7$	$9$	$11$	$12$	$14$	$16$	$19$
Element	$Na$	$Mg$	$Al$	$Si$	$P$	$S$	$Cl$
At. wt.	$23$	$24$	$27$	$29$	$31$	$32$	$35.5$
Element	$K$	$Ca$	-	-	-	-	-
At. wt.	$39$	$40$	-	-	-	-	-

(N/A) Mendeleev's periodic table was one of the greatest achievements in the development of chemistry. Some of the important contributions are:
$(A)$ Systematic study of the elements:
- It simplified the study of the chemistry of elements.
- Knowing the properties of one element in a group,the properties of other elements in the same group could be easily predicted.
- This made it very useful for studying and remembering the properties of a large number of elements.
$(B)$ Correction of atomic mass:
- It helped in correcting the atomic masses of some elements based on their positions in the table.
- For example,the atomic mass of beryllium was corrected from $13.5$ to $9$.
- Similarly,the atomic masses of indium,gold,platinum,etc.,were corrected.
$(C)$ Prediction of new elements:
- At the time of Mendeleev,only $56$ elements were known.
- While arranging these elements,he left gaps for undiscovered elements.
- He predicted the properties of these elements based on their positions.
- The observed properties of these elements,when discovered later,were found to be similar to those predicted by Mendeleev.

$Group/Element$	$Atomic$ $weight/Note$
$VI$. Tellurium	$127.6$. Higher atomic weight
$VII$. Iodine	$126.4$. Lower atomic weight

(N/A) Mendeleev's periodic law states that the physical and chemical properties of elements are a periodic function of their atomic weights.
Key features of Mendeleev's periodic table include:
$1$. Elements were arranged in order of increasing atomic weights.
$2$. It consisted of $8$ vertical columns called groups and $7$ horizontal rows called periods.
$3$. Mendeleev left gaps for elements that were yet to be discovered (e.g.,Eka-boron,Eka-aluminium,and Eka-silicon).
$4$. It allowed for the systematic study of elements and predicted the properties of unknown elements.

(N/A) The drawbacks of Mendeleev's periodic table are as follows:
$(i)$ Elements with similar properties were placed in different groups,while some elements with different properties were placed in the same group. For example,alkali metals $(Li, Na, K)$ were grouped with coinage metals $(Cu, Ag, Au)$,despite their distinct chemical properties. Conversely,chemically similar elements like $Cu$ and $Hg$ were placed in different groups.
$(ii)$ In some cases,elements with higher atomic weights were placed before elements with lower atomic weights to maintain the grouping of elements with similar chemical properties. Examples include the pairs $(Ar, K)$ and $(Co, Ni)$.
$(iii)$ Isotopes were not assigned separate positions in the periodic table,which contradicts the principle of classification based on atomic weight.
$(iv)$ The position of hydrogen remained controversial,as it shows properties similar to both alkali metals and halogens.
$(v)$ The arrangement of elements in group $VIII$ into three triads lacked a clear justification.
$(vi)$ The existence of even and odd series in the $IV, V,$ and $VI$ long periods could not be explained.
$(vii)$ The periodic table did not provide a proper position for the lanthanides and actinides.

(N/A) Mendeleev classified the elements in his periodic table based on their $Atomic \ Mass$. He could not stick to it firmly because he had to prioritize the similarity in physical and chemical properties of elements over the strict adherence to increasing atomic mass,leading to some anomalies.

(A) Mendeleev's periodic law states that the properties of elements are a periodic function of their $atomic \ mass$.
In contrast,the modern periodic law states that the physical and chemical properties of elements are a periodic function of their $atomic \ number$.

(N/A) Newlands: Awarded the Davy Medal by the Royal Society,London in $1887$.
Glenn $T$. Seaborg: Awarded the Nobel Prize in Chemistry in $1951$. To honor him,the element with atomic number $106$ was named Seaborgium $(Sg)$.

(A) According to Dobereiner's Law of Triads,the atomic mass of the middle element is approximately the arithmetic mean of the atomic masses of the other two elements.
Atomic mass of $Li = 7$
Atomic mass of $K = 39$
Atomic mass of $Na = \frac{Atomic \ mass \ of \ Li + Atomic \ mass \ of \ K}{2}$
Atomic mass of $Na = \frac{7 + 39}{2} = \frac{46}{2} = 23$

(N/A) $1$. Johann Wolfgang $D$öbereiner: Law of Triads
$2$. $A$.$E$.$B$. de Chancourtois: Cylindrical arrangement of elements
$3$. John Alexander Newlands: Law of Octaves
$4$. Dmitri Mendeleev: Periodic Law
$5$. Henry Moseley: Modern Periodic Law

(A) Mendeleev's periodic table consists of $7$ horizontal rows called periods and $8$ vertical columns called groups. Each group is further divided into two subgroups,$A$ and $B$.

(B) Mendeleev arranged the elements primarily on the basis of their $Atomic \ mass$.
He observed that the properties of elements are a periodic function of their $Atomic \ mass$.
For example,he placed $I$ (atomic mass $126.9$) after $Te$ (atomic mass $127.6$) in group-$VII$ based on chemical properties,despite the atomic mass of $I$ being lower than $Te$.

(N/A) Mendeleev predicted the existence of several elements that were not discovered at that time. He left gaps in his periodic table for these elements and named them by prefixing the word '$eka-$' (Sanskrit for 'one') to the name of the element immediately preceding them in the same group.

$Element$	$Mendeleev's$ $Name$
$Gallium$	$Eka-aluminium$
$Germanium$	$Eka-silicon$

(B) Mendeleev's periodic table was primarily based on the following factors:
$(i)$ Atomic mass (Periodic Law): Elements were arranged in increasing order of their atomic masses.
$(ii)$ Similarity in physical and chemical properties: Elements with similar properties were grouped together.
$(iii)$ Formula of compounds: He considered the formulas of hydrides and oxides formed by the elements.

(B) At the time of the construction of Mendeleev's periodic table,the following information was not known:
$(i)$ Internal structure of atoms
$(ii)$ Subatomic particles (like protons,neutrons,and electrons)
$(iii)$ Electronic configuration of elements
Therefore,the concept of atomic number was not known,as it is based on the number of protons.

(N/A) $(i)$ Johann Wolfgang $D$öbereiner
$(ii)$ Law of Triads
$(iii)$ John Alexander Newlands
$(iv)$ Dmitri Mendeleev and Lothar Meyer

(N/A) $(i)$ False: The first periodic table was proposed by Mendeleev,while Dobereiner proposed the law of triads.
$(ii)$ True: John Newlands proposed the law of octaves in $1865$.
$(iii)$ True: Dmitri Mendeleev is credited with formulating the periodic law based on atomic mass.
$(iv)$ False: Mendeleev named Eka-aluminium as Gallium and Eka-silicon as Germanium.

(A) $(i)$ True: $Courtois$ studied the properties of elements and their oxides.
$(ii)$ False: $Li, Na, K$ form $Döbereiner's$ triad,not $Li, Na, Rb$.
$(iii)$ False: $Newlands$ arranged $56$ elements into $7$ groups (octaves),not $18$.
$(iv)$ False: $Mendeleev's$ periodic table was based on atomic mass,not atomic number.

(A) $(1-B), (2-E), (3-A), (4-C)$

(A) At the time $D.I.$ Mendeleev proposed the periodic table,the structure of the atom was unknown. Therefore,statement $A$ is incorrect.

(C) The correct answer is $C$.
According to Mendeleev's periodic law,the physical and chemical properties of the elements are a periodic function of their atomic mass.

(D) Statement $(I)$ is false because the Law of Octaves,proposed by Newlands,arranged elements in the increasing order of their atomic weights,not atomic numbers.
Statement $(II)$ is false because Lothar Meyer plotted physical properties (like atomic volume) against atomic weights,not atomic numbers.

(C) According to $Dobereiner's$ law of triads,the atomic mass of the middle element is approximately the arithmetic mean of the atomic masses of the other two elements.
$1$. For $Li, Na, K$: $\frac{7 + 39}{2} = 23$ (Forms a triad).
$2$. For $Ca, Sr, Ba$: $\frac{40 + 137}{2} = 88.5 \approx 88$ (Forms a triad).
$3$. For $Cl, Br, I$: $\frac{35.5 + 127}{2} = 81.25 \approx 80$ (Forms a triad).
$4$. For $Cl, K, Ca$: The atomic masses are $35.5, 39,$ and $40$. The average of $35.5$ and $40$ is $37.75$,which is not equal to $39$. Thus,it does not form a triad.

(C) "The properties of elements are periodic functions of their atomic weights." This statement is known as $Mendeleev's$ periodic law.