Questions tagged [periodic-table]

This tag should be applied to questions about the layout, history and interpretation of the periodic table, not to questions relating to specific elements or trends within the table. For these, the tags 'elements' or 'periodic-trends' should be used where appropriate.

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Why is scandium not in Group 13 despite being once called "eka-boron"?

When drawing up the Periodic Table, Mendeleyev famously predicted the existence of then-unknown elements such as "eka-boron", which we now know as scandium. However, in the modern Periodic ...
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In school, I learnt that Potassium is the most reactive element in the reactivity series. I thought it was Francium?

In school, I learnt that Potassium is the most reactive element in the reactivity series. In the periodic table, the further you go down the more reactive the elemnt is. If this is true, then shouldn'...
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3 votes
1 answer
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Melting and boiling point of transition-metals, primarily for the groups of Cr and Mn [duplicate]

The NCERT Chemistry book for Grade 12 writes The high melting points of these metals are attributed to the involvement of greater number of electrons from $(n-1)d$ in addition to the ns electrons in ...
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Just how accurate is this XKCD comic about building a real-life periodic table with cubes made up of each element?

I was reading the book “What If?” by Randall Munroe and this part was very intriguing to me. He answered the question in the title and I was curious if his answer was realistic, and if not, which ...
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-3 votes
1 answer
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Doubt regarding trends in modern periodic table [closed]

We know that atomic radius decreases along a period and increases along a group. (Same goes for metallic character) But if we take 2 elements A & B(A is at somewhere in the top and left in ...
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Lead vs Carbon Properties

Lead and carbon are part of the same group on the periodic table, so they have the same number of valence electrons. However, their chemical and physical properties are dramatically different. But why ...
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2 votes
3 answers
830 views

Why an atom is more stable when only sublevels s and p are full?

Supposedly when explaining electronegativity and stability of an element, they tell you that it is more stable if the last level is full. That works up to the third period, but after transition ...
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4 votes
1 answer
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How do the odd proton-number elements originate?

I have a question about the origin of the odd proton-number elements in the periodic table, please. As it is generally thought that the big bang produces hydrogen first, and then hydrogen combined to ...
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6 votes
1 answer
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Is there a canonical variable for period and group?

For example, "Z" is the standard symbol for atomic number. I'm writing a manuscript that uses the group and period of elements within some equations, and so far I'm just denoting them as $G_{...
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-2 votes
1 answer
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Why does $\mathrm{NO_3}$ have charge $1-$? [closed]

I'm given the following problem: Write the molecular equation for the reaction $\mathrm{Iron\;(III)\; Nitrate\; and\; Sodium \;Phosphate}$ I begin by attempting to determine the empirical formula of ...
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calculation of relative atomic masses in the periodic system [closed]

If I now want to calculate the relative mass of c-13 based on the definition m(c-12) = 12amu, I need the q/m values of c-12 & c-13, where do I find these (I've looked everywhere on the internet)? ...
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Does fluorine have 5 or 7 active valence electrons?

In a paper on chemical periodicities of elements, Cao et al. show the number of valence electrons in a periodic table (https://doi.org/10.1515/pac-2019-0901). Apart from Boron and Aluminum shown as ...
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How to know the number of valence electrons of f-block elements? [closed]

I kinda know how to get the valence electrons for s/p/d- blocks but i don't know about the f-block. Wikipedia says that valence electrons for f-block is ns + (n-1)d + (n-2)f, so is it true? If so can ...
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1 vote
1 answer
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How to know the group number from the ionization energy?

The successive ionization energy of the first four electrons of a representative element are $\pu{738.1 kJ/mol}$, $\pu{1450 kJ/mol}$, $\pu{7730 kJ/mol}$ and $\pu{10500 kJ/mol}$. Characterize the ...
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atomic structure - why only hydrogen be separately written in periodic table [duplicate]

The other exception is hydrogen. It has only one s-electron and hence can be placed in group 1 (alkali metals). It can also gain an electron to achieve a noble gas arrangement and hence it can behave ...
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Naming of the chemical elements and original sentences by the discoverers

Does anyone recall a printed or an online compilation where the names of all the chemical elements are listed along with the original sentence, from a research paper, containing the name of the ...
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Do Ions with less stability have less energy of ionization than those who are stable?

Problem. I've come up with the strange example of the third energy of ionization of both $\pu{Mg}$ and $\pu{Al}$, the standard logic that is to be applied on any problem of "which element has ...
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What would happen if electrons were spin-1?

We were speaking about this in class, but I can't understand it quite well. What would happen if (hypothetically of course) the allowed $m_s$ values were $-1$, $0$ and $1$? What impact does this have ...
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Doubts regarding Mole concept and Avogadros number [closed]

So I am really confused about simple topics like mole and Avogadro Here is my oversimplified view So mass of 1 atom of elements in grams was not in whole numbers and it was difficult using em for ...
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Why is effective nuclear charge used to explain the periodicity of size of atoms and ions?

Why is effective nuclear charge used for explaining the periodicity of size of atoms and ions, even though radius depends upon many other factors? The size of $\ce{Na+}$ is smaller than that of $\ce{...
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Does the Atomic Mass listed for each element on the periodic table reflect the relative abundances of their isotopes on Earth? Or in the Universe? [duplicate]

Somehow, I cannot find a site or book or paper explaining exactly how the average atomic masses for the elements on the periodic table are weighted.... I posted a question either here or on Physics S....
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Relation between Ionization energy and reactivity

So I was learning about the periodic table where I came across the topic of ionization energy. As a general trend the Ionization energy decreases as we move down a group with a few exceptions such as ...
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1 vote
1 answer
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What is the name for the relationship between two elements in the same group?

I'm looking for a specific term which can be used to describe two elements in the same group of the Periodic Table. This would be useful since elements in the same group tend to have similar chemical/...
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7 votes
1 answer
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Spontaneity and nature of attack of fluorine gas on aluminum

What is the nature of the reaction of attack of fluorine gas on aluminium metal? Is it spontaneous in nature? I have studied reactions of halogens on aluminium, but it had no information about ...
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Color of Flame Test for Alkali Metals

Lithium is known to have the highest ionization energy among Group 1 elements. Also, characteristic colours in the flame test arise due to the excitation and de-excitation of electrons. Then why ...
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7 votes
4 answers
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Why are there only 7 periods in the periodic table? [duplicate]

Is seven a hard theoretical limit (there can’t be an eighth period) or is it there just because we haven’t discovered/synthesized anything beyond that?
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2 votes
2 answers
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How do we know the natural abundance of isotopes on Earth?

Without knowing the Average Atomic Mass or the percent abundance, how do we know that Protium is the most prevalent hydrogen isotope? What methods did scientists use to come to this conclusion? How ...
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Predict the valence configuration of this element using the first five ionization energies [closed]

If the first five ionization energies of an element are, respectively: $\pu{1.09 kJ/mol}$, $\pu{2.35 kJ/mol}$, $\pu{4.62 kJ/mol}$, $\pu{6.22 kJ/mol}$ and $\pu{37.83 kJ/mol}$, to which group of the ...
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Why is Cu(II) more stable than Cu(I)? [duplicate]

Seeing Copper has an exceptional electron filling in its valence shell(4s1 3d10), the way I see it is that on +1, a d10 configuration should be more stable and hence easier to attain than a d9 which ...
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2 votes
1 answer
421 views

Why does the ionization enthalpy of elements across a period not follow a regular pattern while the atomic size always decreases?

First of all, I would like to mention that I am only talking about elements that aren't from the d or f blocks. In order to further elaborate on my question, I would like to take the third period as ...
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2 answers
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Transition metals with closed shells

From wiki page about valence electrons: An atom with a closed shell of valence electrons (corresponding to an electron configuration $s^2p^6$ for main group elements or $d^{10}s^2p^6$ for transition ...
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6 votes
1 answer
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Why can’t lanthanum through lutetium and actinium through lawrencium all be in group 3?

In 2015, IUPAC established a task force to “deliver a recommendation in favor of the composition of group 3 of the periodic table.” Not much about their decision-making process has been made known to ...
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1 vote
1 answer
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How would someone in 1917 describe elements 43, 61, 72, 75, 84, 85, 87, 89, and 91? [closed]

https://books.google.com/books?id=aaELAAAAYAAJ&printsec=frontcover#v=onepage&q&f=false Notice the list of elements on pages 62–63. It includes a short description of each element's "...
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2 votes
1 answer
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Find the Ionisation Potential and Electron affinity of X

$N_0/2$ atoms of $X_{(g)}$ are converted into $\ce{X^+_{(g)}}$ by energy $E_1$. $N_0/2$ atoms of $X_{(g)}$ are converted into $\ce{X^-_{(g)}}$ by energy $E_2$. Hence ionisation potential and electron ...
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1 vote
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Why is the ionization energy of radium higher than barium? [duplicate]

The ionization energy of radium is higher than barium. The reason provided is that occurs fue to lanthanide contraction. But, Radium isnt a member of lanthanide series. How come we say that lanthanide ...
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0 votes
1 answer
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Contradiction of general rules of bond character [closed]

The rules the ionic character of metal halides of halogens is given in order $\ce{MF > MCl > MBr > MI}$. While judging polarisability we say that a compound that has large cation and small ...
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How can an element have two outermost shells incomplete? [closed]

As I read my book, I saw its written that the Transition metals have two outermost shells incomplete. But , as I had read earlier, that shells are filled in stepwise manner. So how is this possible? ...
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How to determine the number of electron in a shell [duplicate]

My textbook has been mentioned that the maximum number of electron in a shell is 2n² and the octet rule. It has also said that period number signifies the number of electron shells of an element and ...
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1 answer
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Determining electronic configuration [closed]

One writes the electronic configuration in terms of shells, spdf subshells, orbitals, and spin of electrons. There are exceptions to principles we know. How does one confirm that the way of writing is ...
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14 votes
1 answer
549 views

How did Mendeleev know elements from compounds or mixtures?

I read that Mendeleev initially thought didymium was an element, but it was actually a mixture. How did he know the rest of the chemicals in the periodic table were elements and not compounds, ...
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Lewis structures and chemical-compound formulas [closed]

In the Lewis structures listed below, M and X represent various elements in the third period of the periodic table. Write the formula of each compound using the chemical symbols of each element: a. b. ...
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4 votes
0 answers
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What is the correct electronic configuration of darmstadtium?

Some of the places, the electronic configuration of darmstadtium ($\ce{Ds}$) is given as $\mathrm{6d^9 7s^1}$ while at some other places, it is $\mathrm{6d^8 7s^2}$. Which among the two is correct?
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3 votes
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why lawrencium is placed in f-block elements although its last electron enters in 6d-subshell?

The electronic configuration of lawrencium ($\ce{Lr}$) is $\mathrm{[Rn] 7s^2 5f^{14} 6d^1}$. As its last electron enters the $\mathrm{6d}$ sub shell, it should be a part of $\mathrm{d}$-block elements,...
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0 votes
1 answer
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Why there is no position of H and He in Lothar Meyer's curve?

I see Alkali metals occupy the peak points. $\ce{H}$ is not an Alkali metal. There's no $\ce{H}$ in the graph. So no point before $\ce{Li}$. Inert gases occupy place on the ascending portion of graph. ...
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1 vote
1 answer
911 views

Why is ionization energy of indium less than gallium?

In group 13 we observe an irregular trend in ionization energy: B > Tl > Ga > Al > In. Gallium has a filled 3d subshell, but indium has a filled 4d and 3d subshell. Thus it should have more poor ...
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5 votes
1 answer
883 views

Why is platinum denser than gold?

The atomic masses of gold and platinum are 196.96657 u and 195.084 u respectively, meaning that (on average) an individual gold atom is heavier than an individual platinum atom. At the same time, the ...
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1 vote
0 answers
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Difference in a array of probability density plots for the electron in its lowest-energy states of Hydrogen atom [closed]

Dynamic Periodic Table If you visit Dynamic Peridic Table, You will notice that for n=4 l=3,2 m=0,0, and n=2,l=1, m=0 there is a difference in the probability density plots for electron in its ...
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0 votes
1 answer
662 views

Comparing Electron affinity and electron gain enthalpy at 0 K

In my book it is given that first electron gain enthalpy is greater than second for elements. Should we compare the magnitudes in such cases or the actual numbers with signs? Does the same comparision ...
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5 votes
1 answer
659 views

Why aren't Boron and Aluminium assigned to group 3 of periodic table? What determines the group? [closed]

I've been curious about this 3D representation of the periodic table "Mendeleev's Flower" and was trying to study it, wondering if it reveals any regularities that are not obvious from classic ...
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2 votes
0 answers
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Is strontium more metallic than sodium? If yes then why?

I got an MCQ in my examination, "Which one of the following is more metallic?" and the options were Sr, Na, Be or Aluminium. I know that sodium is more metallic than Be or Al but my mind stuck on ...
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