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.

Filter by
Sorted by
Tagged with
0
votes
1answer
54 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
59 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
83 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: −14 eV, −28 eV, −94 eV, −218 ...
1
vote
0answers
25 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) ...
2
votes
1answer
51 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 ...
0
votes
1answer
82 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 ...
-2
votes
1answer
115 views

What is so special about Beryllium (Be) and Magnesium (Mg)? [closed]

I am asking this because after studying periodic properties and trends of elements I have come to an understanding that these two elements ($\ce{Be \& Mg}$) are many of the time exception to the ...
0
votes
0answers
16 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
84 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
84 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 $\ce{Bi + O2 → Bi2O3}$. However, it is to my understanding ...
-1
votes
1answer
51 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 ...
0
votes
0answers
261 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
134 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
46 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. ...
1
vote
0answers
79 views

Why is the Ionization Energy of Germanium less than that of Silicon?

I've read that in the 13th period, Ga has higher I.E. than Al because of the filling of the d-orbitals in Ga. The text said they have low penetration,hence they don't shield well and the effective ...
0
votes
0answers
18 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
58 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 ...
0
votes
0answers
28 views

Comparing the EA [duplicate]

What is the electron affinity trend for the oxygen family? I am interested in the question above. I am aware that EA of O $>$ EA of S, but what about the others? Which is having more EA: O or Se? ...
3
votes
1answer
104 views

What is the electronic configuration of La⁺? [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
1k 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
174 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
435 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
130 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
26 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
639 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
43 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 ...
3
votes
1answer
1k 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
75 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
1answer
214 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 ...
1
vote
0answers
421 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
2k 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
26 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
79 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
53 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
1k 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 ...
4
votes
0answers
1k views

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

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 ...
4
votes
2answers
492 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 ...
0
votes
1answer
4k 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 ...
0
votes
1answer
5k 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 ...
0
votes
1answer
1k 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 ...
0
votes
1answer
374 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 ...
6
votes
2answers
1k 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 ...
0
votes
3answers
557 views

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

Why stop at 118 , Why aren't any more stable elements possible ?
1
vote
2answers
3k 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 ...
3
votes
0answers
1k 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 ...
-4
votes
1answer
1k 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 ...
-3
votes
1answer
283 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?
0
votes
0answers
2k 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 ...
2
votes
0answers
76 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?