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.
203
questions
14
votes
1answer
442 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, ...
-3
votes
1answer
64 views
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.
...
0
votes
0answers
48 views
What is the correct electronic configuration of darmstadtium (Ds; Z = 110)?
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?
2
votes
0answers
33 views
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,...
-1
votes
1answer
35 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.
...
0
votes
1answer
55 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 ...
0
votes
0answers
18 views
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 ...
4
votes
1answer
138 views
Why is platinum denser than gold?
The atomic masses of gold and platinum are 196.96657Ā u and 195.084Ā u respectively, meaning that (on average) an individual gold atom is heavier than an individual platinum atom.
At the same time, the ...
1
vote
0answers
30 views
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 ...
0
votes
1answer
109 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 ...
4
votes
1answer
108 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 ...
2
votes
0answers
59 views
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 ...
0
votes
1answer
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 ...
0
votes
1answer
319 views
What do you mean by “periodic” in the periodic table? [closed]
Modern periodic law states:
āThe physical and chemical properties of the elements are periodic
functions of their atomic numbersā.
But I don't think this is so! (Forgive me for my stupidity. But ...
0
votes
2answers
326 views
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) + ...
1
vote
1answer
166 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 ...
3
votes
1answer
130 views
Structure of the periodic table
The periodic table I understand is arranged by order of increasing atomic number after Henry Moseley's X-ray experiment.
But I also learned that the periodic table also has its shape due to the ...
0
votes
1answer
282 views
Effective nuclear charge and Ionization energy
A common reason given on why 3rd ionization energy > 2nd > 1st is because of increasing effective nuclear charge.
As per my book $Z_\mathrm{eff}$ = Atomic number $-$ Number of inner electrons.
Now ...
3
votes
1answer
280 views
The boiling points of Alkali metal group
As I know, the melting points of Alkali metals decrease down to the group due to decreasing of the energy of the metallic bond.
But according to my understanding, after it has become to liquid the ...
4
votes
1answer
111 views
How would one determine an element simply by looking at its binding energy?
I am self studying MIT OCW chemistry 5.111 2014, one of the lecture questions states the following:
Consider a neutral atom with 8 distinct electron binding energies: ā14 eV, ā28 eV, ā94 eV, ā218 ...
1
vote
0answers
33 views
Electrons and Atomic Mass
Is the mass of electrons covered when talking about atomic mass. For example, the mass of Carbon is $12.011\space\text{amu}$. If this is including the mass of electrons (assuming the atom is neutral) ...
4
votes
1answer
153 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 ...
1
vote
1answer
866 views
Comparison between van der Waals radius and metallic radius
I was reading about different types of atomic radius. It was written that if any atom can possess all the three types of radius, then van der Waals radius will be greater than metallic radius. However ...
0
votes
0answers
20 views
What trend exists in the enthalpy change of reaction of group 2 carbonates with HCl
I am currently investigating the trends in enthalpy change of the reaction of group 2 carbonates with HCl. As per ion polarization theory there should be an upward trend in stability and thus a ...
-6
votes
2answers
252 views
Why is atomic number unique? [closed]
We all know that atomic number of an atom is "unique" just like fingerprint. And no two elements can have same atomic number. But how can we be So sure that no two elements can have same atomic number?...
0
votes
2answers
259 views
Why is the product of the reaction “Bi + O2” Bi2O3 instead of Bi2O5?
I am stuck on a homework question that states:
A piece of solid bismuth is heated strongly in oxygen.
The answer key states the answer as $\ce{Bi + O2 ā Bi2O3}$. However, it is to my understanding ...
-1
votes
1answer
60 views
The reaction of Group 14 to get its full shell
I was learning about group 14 of the periodic table and in the course, on Alison (link at the bottom), it said a reaction of the elements in group 14, they use group 4, would consist of sharing ...
1
vote
1answer
934 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, ...
0
votes
1answer
416 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 ...
0
votes
1answer
254 views
Why is the valency of the Calcium (Ca) Bohr model, set to 2 electrons, instead of 1 electron for stability? [duplicate]
This is an Ascii table for the elements on the 4th period (row) of the periodic table, and distribution of electrons in each orbit.
...
0
votes
0answers
25 views
n+l rule for first member of lanthanide and actinide series
as we all know that if the value of $n+l$ is same then the orbital with lower value of $n$ will get filled first so in case of first member of lanthanide series the configuration is $(\ce{Xe})\mathrm{...
1
vote
0answers
106 views
Predicting atomic weight and density of calcium [closed]
I have a question from school:
Assuming that the element Ca had not been discovered, predict using the properties of the known element surrounding Ca its own properties such as its atomic weight ...
3
votes
1answer
192 views
What is the electronic configuration of Laāŗ? [closed]
Second IP of La is most likely to second IP of which element:
(1) Be
(2) Ba
(3) Ca
(4) Zn
The given answer is calcium. I don't understand if the 6s electron or the 5d electron leaves on ...
0
votes
1answer
3k views
Effective nuclear charge of oxygen atom (O) vs oxygen anion (O2-)
The size of an anion is greater compared to its parent atom because former's effective nuclear charge is lesser than that of latter.
I found on wikipedia that the effective nuclear charge can be ...
-1
votes
1answer
572 views
why lithium is less reactive than sodium? [duplicate]
Lithium lies above sodium in a group and is also smaller in size. According to periodic trend reactivity decreases from left to right in period and down the group.
1
vote
0answers
666 views
Definition of early vs. late transition metal
Is there an accepted definition of an early or late transition metal? I think the late transition metals start at Group 8 (including Fe), but others have said Fe is not a late transition metal. I'm ...
2
votes
2answers
144 views
How will the periodic table change due to redefinition of the kilogram (May 2019)?
The definition of a kilogram has recently been changed. What effect, if any, will this change have on data on the periodic table?
1
vote
0answers
33 views
Difference in Periodic Tables in Block Formation (split in d-block) [duplicate]
I had a question. When I was learning Chemistry and blocks in the periodic table, my professors always broke the table down like the image below
Recently, when I looked up the periodic table (in ...
7
votes
3answers
5k views
Confused by notation of atomic number Z and mass number A on periodic table of elements
I'm totally confused by the different conventions and when to use what. In the Periodic Table I see
$$\ce{^{6}_{12}C}$$
However, in books when talking about isotopes I see
$$\ce{^{12}_{6}C}$$
I ...
-2
votes
2answers
1k views
Change in electronegativity order down a group from groups 13-16 to group 17
In general, going down a group Zeff initially increases but then becomes approximately constant, while electrons are in higher n orbitals, hence valence electrons on average further from nucleus, ...
1
vote
0answers
49 views
Exception in trend of increasing ionisation energy across a period
One exception to the trend of increasing ionisation energy across a period in e.g. period 2 is going from N to O. There is no loss of exchange energy in I1 of O, but there is 2K lost in I1 of N, hence ...
4
votes
1answer
4k views
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^...
2
votes
0answers
105 views
Mendeleev periodic table [closed]
Mendeleev accurately predicted the properties of gallium(eka aluminium). In his justification of properties he says(according to image given) the melting point of the element would be low. What could ...
2
votes
2answers
384 views
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 ...
5
votes
2answers
2k views
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 ...
1
vote
1answer
3k views
Which has a higher lattice energy CaO or NaCl? [closed]
I know that as charge increase the lattice energy increases as well. However when the size increases, the lattice energy decreases. Can you please explain this to me? I think it is CaO but i'm not ...
0
votes
0answers
28 views
What are Technetium's physical stress characteristics?
I've looked at periodic and data tables from several sources, but none give mechanical / engineering property data on Technetium. Why is this?
1
vote
0answers
90 views
Is there a definitive model of the Elements as a Periodic Tetrahedral [closed]
i.e. Is there a specific reason why these diagrams exist? Is the "neatness" of the design simply a graphical representation of the mathematical constants, or is there some underlying reason why a ...
0
votes
1answer
60 views
What does it mean that an electron quantum numbers are n1= 4 - l1?
I'm trying to solve some exercises from the 2017 IChO, and the problem 6-A1 states that
in first ionization, an electron with the quantum numbers $n_1 = 4 - l_1$ is removed.
Now, I've never seen ...
1
vote
3answers
3k views
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 ...
