Questions tagged [periodic-trends]
Trends which are observed in the properties of elements as you move along the periodic table in a given direction.
266
questions
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Stability of halogen oxides [closed]
I was studying periodic properties, p-block and came to the following line:-
The higher oxides of halogens tend to be more stable than lower ones
It means high oxidation state halogens (example Cl ...
0
votes
1answer
97 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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votes
0answers
47 views
Relation between reactivity series and electrochemical series [closed]
I have already read answers to the following questions:
Reactivity series of metals
What is the difference between reactivity series and electrochemical series?
But I didn't get what I wanted.
When ...
0
votes
0answers
19 views
How ion size/electronegativity influences strength of an acid
My prof was explaining how we can use the structure of acids and bases to rationalize relative strengths (ie: acid X is stronger than acid Y because ...). He then went on to explain how when ...
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votes
3answers
28 views
Is acidic character related to reducing power?
My book says that the acidic character of halogen acids increases on going down the group because the bond strength decreases, making it easier to release the $\ce{H+}$.
But I also know that $\ce{HI}$...
2
votes
1answer
71 views
Electronegativity of heavier elements of Group 15
While reading about p-block I got to know that in Group 15 elements
electronegativity value decrease down the group but amongst the heavier elements difference is not that much pronounced.
I ...
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votes
1answer
55 views
Atomic radii and why does it decrease in a period [closed]
Why do atomic radii decreases as you move from left to right across a period
0
votes
1answer
86 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 ...
4
votes
1answer
87 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 ...
0
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1answer
43 views
Standard Reduction Potentials and Electropositivity
I was looking through a table of standard reduction potentials and the trend seemed like it correlated with electropositivity. Is it reasonable to qualitatively compare two metals to see which has a ...
3
votes
1answer
68 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
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1answer
34 views
Why does the emission wavelength of sodium appear to be an exception despite the trend for ionisation enthalpies among alkali metals?
The wavelengths for emissions in the visible region for Group 1 elements is as follows:
$$
\begin{array}{lc}
\hline
\text{Element} & λ/\pu{nm} \\
\hline
\ce{Li} & 670.8 \\
\ce{Na} & 589.2 ...
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2answers
89 views
Ionization energy of neon vs its cationic counterpart
Which requires more ionization energy: $\ce{Ne}$ or $\ce{Ne+}?$
It seems to me like it should be neon because of noble gas configuration, but the answer given is $\ce{Ne+}.$ Does this anything to do ...
1
vote
0answers
103 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
19 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
62 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?
...
0
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1answer
2k views
Ionization enthalpy for group 13 elements
The ionization enthalpy for elements along a group generally reduces.
But there is an exception for group 13 elements and the order is not
uniform.
The order is:
B>Tl>Ga>Al>In
According to ...
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votes
1answer
251 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
95 views
Relationship between electronegativity and atomic radius [closed]
Would someone please explain in detail the relationship between the two? I understand that atomic radius is related to ionisation energy but I can't see how atomic radius may be related to ...
-1
votes
1answer
281 views
Which is more metallic: boron or silicon?
I read somewhere that boron is more metallic. Is it correct? If so, can you please elaborate?
The reason why I'm confused is because 2 factors come into play here:
When you move towards right, ...
0
votes
0answers
99 views
Why don't ionization energies vary linearly going down Group 2?
I understand why the 1st ionization energies (1st IEs) of Group 2 elements decrease down the group.
However, why is the difference between 1st IEs of successive elements greater for Be to Ca and ...
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2answers
747 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, ...
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0answers
45 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 ...
0
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1answer
194 views
Why do metals form cations?
metals that have a low number of occupied shells such as lithium and potassium should have a stronger electrostatic attraction to their nuclei, so what causes them to always lose their electrons ...
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0answers
576 views
Ionisation energies of Carbon and Boron
The first ionisation energy of Carbon atom is greater than that of Boron atom whereas, the reverse is true for the second ionisation energy.
In order to explain the above statement I considered the ...
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1answer
941 views
Thermal stability order of NaF, MgF2 and AlF3
I came up with a question to arrange thermal stability order of $\ce{NaF}$, $\ce{MgF2}$ and $\ce{AlF3}$ and I think the answer is $\ce{NaF>MgF2>AlF3}$ because $\ce{Na+}$ has largest ionic radius ...
1
vote
0answers
258 views
Why is fluorine a oxidising agent?
An Oxidizing agent pulls the electron cloud of the substance being oxidized towards itself, for example:
$$\ce{F2 + 2 X- → 2F^- + X2}\qquad (\ce{X} = \ce{Cl}, \ce{Br}, \ce{I})$$
We also know that ...
0
votes
1answer
74 views
Lanthanoid Contraction
Why is the radius of Europium so unusually high and out of the general trend ? Moreover, at different sources I am getting different values of radii. In some (e.g., Wikipedia) the radii are following ...
2
votes
1answer
236 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 ...
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votes
1answer
207 views
Relationship between effective nuclear load and periodic properties
The effective nuclear charge is defined as the net positive charge experienced by an electron in a polyelectronic atom. It can be calculated using the well-known Stars Rule.
Once I have calculated ...
3
votes
0answers
83 views
Why are the Covalent Radii of Ruthenium and Osmium So Similar?
Osmium and Ruthenium have covalent radii 144 and 146 respectively (according to Wikipedia).
How are these values so similar when Osmium has 32 more electrons, with another filled p, s, and f orbital ...
2
votes
2answers
1k views
Density of d-block elements
Something that confuses me slightly is the trends in density when comparing periods 4, 5, and 6 in the d-block. Looking at periods 5 and 6, the density peaks at group 8, with ruthenium and osmium, ...
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votes
3answers
3k views
If Mg(OH)2 is insoluble, why does the reaction of MgO and water produce a slightly alkali solution? [closed]
The equation of the reaction is:
Mg(OH)2 + H2O -> Mg(OH)2.
Why is it that this reaction produces a solution of around pH 9? There are no OH- ions produced.
3
votes
0answers
178 views
H-N-H bond angle in ammonia boron trifluoride adduct
In the reaction:
$\ce{NH3 + BF3 -> NH3-BF3}$ does the HNH bond angle increase or decrease?
Surely, the FBF bond angle decreases because boron changes from $\ce{sp^2 -> sp^3}$. But how can we ...
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votes
1answer
680 views
Why it the electron affinity of beryllium is greater than nitrogen? [closed]
As we know that fully filled electronic configuration is more stable than half filled electronic configuration, so in my opinion beryllium's electron affinity should be less than nitrogen's.
Is my ...
2
votes
0answers
677 views
Second ionization energies of copper(Cu) and silver(Ag)
The ionization energies of copper and silver are
First ionization energy: Cu-745.5 kJ/mol Ag-731.0 kJ/mol
Second ionization energy: Cu-1958 kJ/mol Ag-2073 kJ/mol
Now, looking at the ...
1
vote
0answers
153 views
Comaparing melting points of group 14 elements [duplicate]
I found that melting point of $\ce{Sn(232°C)}$ is less than $\ce {Pb (327.5°C)} $ but i also saw that the bond enthalpy of $\ce {Sn-Sn(187.1 ±0.3 kJ mol^{-1})}$ is more than $\ce{Pb-Pb 86.6 ±0.8 kJ ...
0
votes
1answer
327 views
Octet rule violation in Period 2 elements [duplicate]
My textbook states,
Period 2 elements typically obey the octet rule. Period 3 and later elements can expand their valence shells. Elements in Periods 5 and 6 of the p-block show variable valence (...
0
votes
1answer
609 views
Why is the melting point of hydrogen fluoride lower than that of ammonia?
The melting point of hydrogen fluoride is -83.6°C, as compared to that of ammonia, which is -77.73°C. How does this make any sense?
Both hydrogen fluoride and ammonia show hydrogen bonding, which "...
0
votes
1answer
1k views
Is there any difference between negative electron gain enthalpy and electron affinity?
Electron affinity is the amount of energy "released" during the addition of an electron in the valence shell of an isolated gaseous atom. The sign convention is opposite to that of thermodynamics ...
4
votes
2answers
1k views
Why is the electronegativity of indium greater than that of thallium?
Why is the electronegativity of indium greater than that of thallium?
One possibility which I had assumed was the poor shielding effect by the d and f orbitals which leads to an increase in the ...
1
vote
0answers
197 views
Mismatch in the trends of atomic size and atomic radius
In the periodic table, the atomic radius decreases as we move from left to right in a period. However, the atomic volume should also decrease as a result of the decrease in atomic radius, as volume is ...
4
votes
2answers
556 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
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1answer
6k 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
2k 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 ...
2
votes
1answer
902 views
Why does the stability of hydrides decrease down the group in nitrogen family?
Why does the stability of hydrides decrease down the group in nitrogen family? Does this have to do with the fact that $\ce{NH3}$'s $\ce{N}$ is hybridised ($\ce{sp^3}$) while the rest of the group ...
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 ...
2
votes
1answer
2k views
Difference between basicity and reducing character
My understanding of basicity and reducing character:
Reducing character is the ability of a substance to reduce something else. So it itself must get oxidized. Since $\ce{BiH3}$ has a large radius, ...
