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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Predict the valence configuration of this element using the first five ionization energies

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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Seperation of Elements in Modern Periodic Table

Why are the elements in Modern Periodic Table (Modern Periodic Table/Henery Mooseley Law) categorised into A and B. Also VIII is in none of the division, why?
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1answer
35 views

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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1answer
51 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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1answer
612 views

The number of transition elements

I searched in the internet but most of them said that there are 38 transition metals. But our text book says that group 12 or the group of zinc CAN'T BE COUNTED as transition metals. Which already ...
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1answer
10k views

Why does the second electron affinity has an opposite sign of the first one?

Many first electron affinities are positive, indicating a favourable process, but the corresponding second electron affinities are negative. For example, the first and second electron affinities of ...
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2answers
45 views

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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1answer
440 views

Why does Calcium have a higher ionization energy than Aluminium?

Given their places on the periodic table I'd assume Aluminium has a higher ionization energy, because it has fewer energy levels, and is on a "righter" row on the periodic table, but in reality it is ...
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4answers
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Calling Diamond an element?

Is it scientifically correct to call Diamond an element? Carbon has a wide range of allotropes, so would it be correct to actually just call graphite, diamond etc an element. For that matter, could we ...
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205 views

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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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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Why are there 3 columns in Group VIII of the Periodic Table?

I'm currently reading in-depth about the layout of the Periodic Table, and I wondered why the table has 3 columns in its Group VIII: As I understand, this is an old notation of the table, now ...
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Are the elements lanthanum and actinium considered to be in the d block or the f block of the periodic table?

Many periodic tables place lanthanum and actinium in the f-block of elements, for example, this periodic table from Los Alamos National Laboratory. However, this table from the Royal Society of ...
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1answer
305 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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1answer
54 views

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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Why the melting point increase up to arsenic and then decrease down the group 16? [duplicate]

I am already google this but can't find the answer that staisfy me. I know down the group, mass and atomic size increase which result in increase in van-der-waal forces. But in group 16 the trend is ...
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1answer
30 views

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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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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Why can mercury(I) exist, but not zinc(I)?

Mercury shows variable valency while zinc does not. Its electronic configuration is $\ce{[Xe]\:4f^14 5d^10 6s^2}$. So it can donate the $\ce{6s^2}$ electrons and should only be able to form $\ce{Hg^2+}...
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3answers
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Why are group 1 elements called alkali metals and group 2 elements are called alkaline earth metals?

I was studying the periodic table. My teacher said that Group 1 elements are called alkali metals because their oxides are soluble in water and group 2 elements are called alkaline earth metals as ...
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67 views

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 find density of element metals

I was wondering, how do I determine what metal (element) has the highest density by using the periodic table? Is it possible?
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1answer
801 views

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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1answer
79 views

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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475 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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1answer
2k views

Why is Thorium (At. no. 90) an f-block element at all?

Being an exception of the Aufbau principle, Thorium has an electronic configuration of $\ce{[Rn]}\mathrm{7s^25f^06d^2}$ instead of the expected $\ce{[Rn]}\mathrm{7s^2 5f^2 6d^0}$. Two other elements, ...
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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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1answer
237 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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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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126 views

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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2answers
7k views

Comparing ionic character of group 1 elements

According to Fajan's rule ionic character should increase down the group as the size of cation increase. So it must be $$\ce{LiH < NaH < KH < RbH < CsH}$$ However, the following two ...
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1answer
4k views

Why do some periodic tables have 18 groups while others have 8?

In school I have been taught about the periodic table with 8 groups, representing the number of electrons in the outer shell (with exceptions). But online almost all I can find is periodic tables with ...
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2answers
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Why do heavier elements have smaller specific heat values.

In the periodic table the trend is that as the mass of each element increase's the specific heat tends to go down. This seems to be counter-intuitive because if I am not mistaken as mass increase's ...
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Which orbital participates in bonding of d and f block elements as these are never the outermost orbital?

For example: Yttrium: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d1 5s2 The outermost orbital is the s-orbital but d-orbital is unfilled. How does overlap of orbital take place in YCl3 as d-orbital is beneath ...
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1answer
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How can scientists be certain that there are no undiscovered elements missing from the periodic table from hydrogen to lawrencium?

Scientists are certain that there are no undiscovered elements missing from the periodic table from hydrogen to lawrencium. How? and why?
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1answer
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Why is Promethium the only radioactive Lanthanide?

Why is it that only Promethium (Pm) is the only radioactive lanthanide? I was trying to figure out what percentage of all radioactive elements in the Periodic Table the f-block accounts for, when it ...
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1answer
264 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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2answers
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How can an electron shield another electron of the same subshell?

While I was preparing for my upcoming exams, I stumbled upon this sentence which is bothering me quite a bit: The contraction of the lanthanoids is due to the imperfect shielding of one electron by ...
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315 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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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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Two different electronic configurations for cerium

Depending on the textbook there are two different electronic configurations stated for cerium. On the one hand $$[\ce{Xe}]\mathrm{4f^15d^16s^2}\quad$$ and on the other hand $$[\ce{Xe}]\mathrm{4f^...
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47 views

Is “family” synonymous with “group”? [closed]

Is using the term "family" strictly correct when we mean a group of the periodic table or is it just in general use (and should perhaps be discouraged in favour of using "group" exclusively)? At my ...
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How to determine the chemical state of a reactant or product in a chemical equation?

I am asked this question: Write a balanced equation, including state symbols, for this reaction: $\ce{calcium + hydrochloric acid -> calcium chloride + hydrogen}$ I answered this: $\ce{Ca(s) + ...
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1k views

What do you mean by “periodic” in the periodic table? [closed]

Modern periodic law states: “The physical and chemical properties of the elements are periodic functions of their atomic numbers”. But I don't think this is so! (Forgive me for my stupidity. But ...
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Where can I find a downloadable spreadsheet of element properties?

Sorry for the FAQ, but I really don't know where to find a full spreadsheet for element properties. I mean a table that has one row for each element, and the columns are its properties, such as name, ...
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Why ionisation enthalpy of early lanthanides are expected to be greater than early actinides?

In my book Chemistry Part I (NCERT XII), a statement on p. 232 goes like this: It is evident from the behaviour of the actinoids that the ionisation enthalpies of the early actinoids, though not ...
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2answers
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What is a “period” of the periodic table?

I'm familiar with the periodic table / periodic system, but I wonder why it's called "periodic" since there seems not much periodic about (there seems to be little or no predictability of which ...
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739 views

Why does period 3 of the periodic table contain 8 elements instead of 18?

Period 1 of the periodic table contains 2 elements ($1s^1$ and $1s^2$). Period 2 contains 8 elements ($2s^1$, $2s^2$, $2p^1$, $2p^3$, ..., $2p^6$). By the same argument, period 3 might contain 18 ...

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