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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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1answer
33 views

How can an electron sheild 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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0answers
79 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 ...
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1answer
95 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 ...
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0answers
22 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?
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0answers
70 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 ...
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1answer
35 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 ...
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1answer
88 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 ...
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0answers
440 views

How to quickly predict the group of elements with atomic numbers 117 and 120?

The elements Z (atomic number) = 117 and 120 have not yet been discovered. In which group would you place these elements? I tried to write their electronic configurations but it was too tedious and I ...
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1answer
129 views

What is the true depiction of the periodic table?

Normally with the periodic table the lanthanide series is separated out because it's long and would make the table wide. I looked for an expanded version and found this: I found it kind of strange ...
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1answer
921 views

Rule to determine the total number of elements in a period [closed]

If each orbital can take maximum of 3 electrons, then total number of elements in 2nd and 4th periods respectively are = ? I am not aware of the rule which helps to determine the total number of ...
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1answer
2k views

Why does oxygen have less negative electron gain enthalpy than sulphur? [duplicate]

Oxygen has less negative electron gain enthalpy than sulphur. This statement is given in my book with a short reason: due to compact size of oxygen I'm unable to understand why. I would ...
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0answers
25 views

Why doesn't the Atomic mass number(u) represent the exact mass of 1 mole of a given element? [duplicate]

From what i know, the Atomic mass number(u) of each element in the periodic table is supposed to show the grams per mole of that atom. but when i take the combined masses of every neutron, proton ...
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1answer
566 views

Why does hydride acidity increase across period and down group in periodic table?

Why exactly does hydride acidity increase across period and down group in periodic table? What is the explanation with respect to electrons? I can't figure this out because for 1st period etc H is an ...
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1answer
176 views

Why is the number of protons and neutrons equal to the atomic mass rounded?

The mass number is defined as the NUMBER of protons and neutrons. Electrons aside, why does the number of protons and neutrons equal the atomic mass rounded to the nearest whole number? That would ...
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2answers
634 views

Why do all atomic masses have decimals if there are some elements that don't have isotopes?

I understand that the way to calculate the atomic mass is to obtain a weighted average of the masses of all the isotopes of an element. I also understand that there are about 26 elements that are ...
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3answers
241 views

Why are there only less than 120 elements out there ? [duplicate]

Why stop at 118 , Why aren't any more stable elements possible ?
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2answers
410 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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0answers
542 views

Comparison between Boron Nitride and Graphite: Interlayer distance

Boron-nitrogen chemistry has attracted significant attention, partly because a B–N unit is isoelectronic with C–C. Furthermore, the radius of carbon and its electronegativity are roughly the average ...
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1answer
812 views

Trends in ionization energy in the second period [closed]

Question Which element among the following has the highest ionisation energy: fluorine, oxygen, neon. I know that all these elements belong to period 2 and ionisation energy increases from left ...
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1answer
85 views

How to calculate the position of an element from its atomic number? [closed]

How to calculate the place of of a element if know their atomic number in a periodic table?
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0answers
795 views

Abnormal ionisation energy trend: Group 13 and 14

I was going through some ionisation energy data, where I came across the following: Ionisation energy order for Group 13 and 14: B > Al ≈ Ga > In < Tl C > Si > Ge > Sn < Pb What could be the ...
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0answers
71 views

is there any evidence that there are ~75 extra elements on the periodic table? [duplicate]

there are 118 currently existing elements on the periodic table, and recently I've found like 77 elements that quote on quote "may exist" on our periodic table. Is this true?
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1answer
320 views

Elements in the lanthanide and Actinide series [duplicate]

How many elements are there in lanthanide and Actinide series? My big doubt is does the 57th element Lanthanum and 89th element Actinium include in it? In some periodic table the entire 57-71 is ...
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1answer
566 views

Why do the d suborbitals start at 3d instead of 4d?

Why do the suborbitals for d start at 3 instead of four? It is in the fourth row on the periodic table and all other suborbitals start according to the row on which they are located except for d. Why ...
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1answer
340 views

Why doesn't D block contraction affect the other P block groups 14 15 16 etc

Usually we come across anomalies in the trends of periodic properties for example the size [Atomic radius value from Raymond Chang Chemistry 9th Edition] of Gallium (135 pm) is smaller than Aluminium (...
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1answer
151 views

Should I provide a citation for atomic masses?

I am writing my first lab report ever, and the handbook I was given did not say anything in particular about this issue. I will use the atomic masses for my calculations and I am not sure if I should ...
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0answers
109 views

What do you chemists need from a periodic table? [closed]

I am developing a website and later on an app with the periodic table. The reason I started was that I thought almost all the other periodic tables was awfully ugly. I do not only want to make it a ...
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1answer
54 views

Quickly deduce block (s, p, d …) from atomic number [closed]

A question from previous year papers of IIT JEE. There's not enough time to write the electronic configuration in the exam. Please suggest a quick, objective approach.
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0answers
733 views

Non existence of B3+ in solution [closed]

I read that B3+ ions do not exist in aqueous solution, because hydration energy cannot compensate for the sum of first three ionisation energies. This leads me to the following questions: If boron (...
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2answers
7k views

Find atomic number given the group and period [closed]

I want to find the atomic number of an element in a short way, when I know the exact group and period of that element. For instance; there is a question in our textbook to find the atomic number of ...
1
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1answer
199 views

Are halogens a further classification of non-metals, or are they another group themselves? [closed]

I've searched many pages in the internet, and many just classify halogens (Grp 7A) as non-metals. However, my teacher classified them as another group in the periodic table, and when asked which ...
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1answer
81 views

Do the spins of outer orbitals block measurement of spin of inner orbitals?

Do the outermost s1 and s2 electrons block an outside observer from measuring the larger inner group orbitals for elements heavier than Nitrogen (for instance, would Chromium's 4s1 electron or ...
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0answers
95 views

Halides in s-block elements [closed]

What is the reason behind the following statement: The $Δ_fH^\circ$ for the fluorides become less negative as we go down the group while the reverse is true for chlorides, bromides and iodides.
3
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1answer
855 views

On the periodic table: Why are groups of elements organized by 'letter' [duplicate]

Why are the groups of elements on the periodic table organized into areas represented by the letters s,p,d,f,g, and h? What does this mean?
3
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1answer
749 views

Mendeleev's predictions

While studying about Mendeleev's periodic table in my textbook( class 11 NCERT chemistry), I have studied that Mendeleev has predicted some elements like Eka-boron(scandium), Eka-Aluminium(Gallium),...
8
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2answers
2k views

Why are metalloids found in a zig-zag line on the periodic table

I am confused about the zig-zag pattern of metalloids in the periodic table. Why are metalloids arranged in a zig-zag line? Can anyone answer my question?
3
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0answers
71 views

What proof is there that the “Island of Stability” exists?

Often I see people talking about an "Island of Stability" existing for super-heavy elements on the periodic table, but I don't see any reason to thinks this exists? Surely the heavier you go the more ...
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0answers
262 views

Why group 13 elements don't show +2 as their major oxidation state?

These are the things I understand: 1) Group-13 elements show +1 and +3 as their major oxidation states(OS). 2) The general configuration of G-13 elements is $ns^2$ $np^1$. 3) In the ...
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0answers
62 views

Trends in Slater's constant

I am aware of the various Slater rules to calculate the effective nuclear charge, $Z_\mathrm{eff}$ However, how can I decide the order in which the orbitals 2s, 3s, 3d, 3p, 4d, and 4f stand when ...
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1answer
582 views

Last electron of a transition element

The electronic configuration of nickel is Ni: [Ar] $3d^84s^2$ Here, while writing the configuration, we fill the 3d after 4s.Hence the 28th electron enters the d orbital. But $\ce{Ni+}$: [Ar] $...
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2answers
283 views

What organizational methods pre-date the Periodic Table?

Dmitri Mendeleev noticed patterns in elements which allowed him to design the periodic table which ultimately led to the modern periodic table. How were elements organized before this? Was there any ...
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1answer
102 views

Why don't elements having the same valency as Carbon bond so readily?

I haven't been in touch with Chemistry as a subject of study for several years now. Still- if I remember correctly, Si, Ge, Sn, Pb all have same number of electrons as Carbon in their outer orbits. ...
3
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1answer
230 views

Good collection of images showing periodicity of the Table?

Mendeleev's recognition of the periodicity of atomic trends was a milestone of human understanding, the detection of a pattern in what had appeared to be chaotic data. I think the significance and ...
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0answers
1k views

Comparing electronegativities of aluminium and gallium

If I were to compare the electronegativities of Al and Ga, shouldn't I be saying that the electronegativity of elements (in general) decreases down the group, I say this by thinking of the position of ...
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0answers
1k views

Bond Energy in P-O , S-O , Cl-O

My text says that Bond energy between P-O , S-O , Cl-O follows the trend P-O < S-O < Cl-O. But I think it should be a reverse of what's given because more the electronegativity difference ...
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1answer
2k views

What is the difference between metaphosphoric acid and phosphonic acid?

Are metaphosphoric acid and phosphonic acid the same? I have been told that they're same BUT the structures online are different. Metaphosphoric acid has formula: $\ce{(HPO3)_n}$ phosphonic acid ...
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1answer
6k views

Electronic configuration of uranium

I read that the electronic configuration of uranium is [Rn] 5f³ 6d¹ 7s² . Given that the subshells fill in the order 5f --> 6d, why is the 5f subshell only partially filled? Why do electrons fill ...
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1answer
212 views

Why is UuX used as a symbol for unnamed elements on the periodic table?

Until recently, the last few elements on the periodic table had the chemical symbols (now they have formal chemical symbols!): Uub, Uut, Uuq, Uup, Uuh, Uus, and Uuo Why did they have these temporary ...
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0answers
92 views

absorption spectrum of water at different wavelengths [closed]

I know I can get the visible absorption spectrum of water https://en.wikipedia.org/wiki/Water_absorption But how does one go about getting and testing what the absorption spectrum is for a glass of ...
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2answers
18k views

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 ...