Questions tagged [periodic-trends]
Trends which are observed in the properties of elements as you move along the periodic table in a given direction.
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trends of periodic table
Which would be the correct option: In a periodic table from left to right in a period,
A) the atomic radius decreases
B)first decreases then increases (because of group 18 elements)?
I was solving ...
4
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2answers
801 views
Why is fluorine a oxidising agent? [closed]
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 ...
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1answer
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The quantum mechanics behind periodicity of elements
Especially in high school/first-year undergraduate chemistry courses, we learn with great dedication the periodicities along groups and periods. There are various useful and interesting trends.
I ...
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What is the periodic trend of Zeff across the periodic table? [duplicate]
So I was watching a vedio of this topic on youtube.
They didn't explained it in detail that what what happens when we go from left to right or top to bottom. And why the Z eff of Na=K=Rb=Cs
And I'm ...
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0answers
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What is the periodic trend of effective nuclear charge across the periodic table? [closed]
So I was watching a vedio of this topic on youtube.
They didn't explained it in detail that what what happens when we go from left to right or top to bottom. And why the Z eff of Na=K=Rb=Cs
And I'm ...
0
votes
1answer
38 views
Why is boiling point of Ammonia greater than Arsine?
I have previously read that the boiling point of Stibane(SbH3) is greater than Ammonia(NH3) as ammonia is gas at room temperature and no hydrogen bonding exists in the gaseous form of NH3.
Hence, as ...
7
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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 ...
13
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1answer
700 views
Why doesn't ionization energy decrease from O to F or F to Ne?
I know that in general, the first ionization energy increases across a period due to increasing nuclear charge, reasonably constant shielding & decreasing atomic radius.
From N to O, however, the ...
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8k 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 ...
1
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1answer
94 views
Question on d block contraction
For size trend down a group, it is known that:$$Al\gt Ga$$
Due, to d block contraction of gallium.
Why isn't this the case when it comes to silicon and germanium?
Won't the poor shielding effect from ...
1
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1answer
41 views
Tendency of formation of complexes in Group-1 elements
My book states the following:
Down the group(Group-1), tendency to form complexes decreases due to decrease in charge density$\bigg(\frac{\text{charge}}{\text{radius}}\bigg).$ This results in ...
5
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1answer
403 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 ...
5
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3answers
6k views
Halogen Oxyacid Trend (acid strength)
Why is $\ce{HClO4}$ more acidic than $\ce{HBrO4}$? But $\ce{HCl}$ is less acidic than $\ce{HBr}$? What determines the acidity? Is it the concentration of $\ce{H+}$? If so, how do these trends develop ...
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2answers
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Why is the melting point of magnesium oxide higher than aluminium oxide?
There's a graph of the melting points of period three oxides. The melting point of magnesium oxide is several hundred Kelvin higher than aluminiumoxide. I can't find any explanations for this on the ...
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1answer
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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 ...
0
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1answer
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Why does this formula work?
My teacher gave us a formula for determining if a M-O-H like compound will act like a base or not.without explaining much.
Base if:$$|\chi_o-\chi_M|\gt|\chi_o-\chi_H|$$
Flipped inequality if acid.
I ...
0
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1answer
253 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 ...
2
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2answers
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Why is Aluminium oxide amphoteric?
I was reading my book, in which it mentioned that aluminium and gallium oxides are amphoteric and and indium and thalium oxide are basic in their properties.
But no explanation was given.
My main ...
2
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2answers
3k 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, ...
2
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1answer
29 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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1answer
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Reactivity Dilemma of elements [closed]
While learning Periodic Properties, I stumbled upon a doubt regarding reactivity of elements of period 2 and period 3.
(I am denoting reactivity, of any $X$ element as $R_{X}$.)
For reactivity of $s-...
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1answer
2k views
Why do atomic radii decrease across a period? [closed]
It's said that atomic size/radius decreases across a period, in spite of addition of electrons. But how does this actually work?
6
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1answer
381 views
Why is the electronegativity of potassium and rubidium same?
The electronegativity of potassium and rubidium is reckoned at 0.82 for both. Why is it same for both of them? Shouldn't it be less for rubidium as compared to potassium owing to the addition of one ...
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1answer
984 views
Is the magnitude of ionisation enthalpy and ionisation energy is same?
In my textbook it is written that ionisation energy and ionisation enthalpy are two different quantities. ionisation energy is the amount of energy provided to extract an electron from the outermost ...
2
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3answers
1k views
How do atomic radius and nuclear charge influence ionisation energies?
This is actually a multiple choice question.
Why is the first ionisation energy of neon higher than that of fluorine?
A: Fluorine is more electronegative than neon
B: Neon has a complete octet, but ...
10
votes
3answers
6k views
Why is the boiling point of heavy water more than that of normal water?
In class we learnt that the London forces become stronger as the relative molecular mass increases. Not just as in organic chemistry but in things like the halogens.
However, as I understand, the ...
5
votes
1answer
343 views
Covalent atomic radii: oxygen vs nitrogen
Many books state that $R_\ce{N} > R_\ce{O}$ which is in accordance with the general trend. However, some books say that $R_\ce{O} > R_\ce{N}$ because of repulsion caused by pairing of electrons.
...
4
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3answers
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Why do the melting points of Group 15 elements increase upto Arsenic but then decrease upto Bismuth?
The boiling points of group 15 elements increase on going down the group (or, as size increases) but the same is not true for the melting points. The melting points increase from $\ce{N}$ to $\ce{As}$ ...
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3answers
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Why is lithium the most reducing alkali metal, and not caesium?
Caesium has a larger size, and the effective nuclear charge that the valence electron experiences will be far less compared to that of lithium's, right? But lithium is still considered the strongest ...
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1answer
2k views
Trend in reducing property of dioxides
I am not sure of the explanation for the following statement:
The reducing property of dioxides of group 16 elements decreases from $\ce{SO2}$ to $\ce{TeO2}$.
Is the statement valid? If yes, how ...
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2answers
499 views
Why does hydrogen have a lower ionization energy than fluorine?
I found here that the ionization energy of hydrogen is $\pu{1312kJ/mol}$ and for fluorine, it is $\pu{1681kJ/mol}$. Now clearly, from the data, we can see that hydrogen has a lower ionization energy ...
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1answer
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Electron affinities of the chalcogens and halogens
Here are the electron affinities of the 16th and 17th groups.
The general trend for electron affinity down the group is that it decreases because of the increase in atomic radius.The exception of $\...
2
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1answer
13k views
Regular decrease in the atomic radius of 3d series
While comparing atomic radius, two factors are important:
A. Decrease in size due to increase in effective nuclear charge
B. Increase in size due to increase in shielding effect
I was surprised to ...
3
votes
1answer
117 views
Is there an opposite to shielding effect? [closed]
I recently read about shielding effect and lowering of effective nuclear charge due to penetration of other electrons. I wonder while doing calculations involving Slater's rules the electrons from ...
4
votes
1answer
199 views
Why is platinum denser than gold?
The atomic masses of gold and platinum are 196.96657 u and 195.084 u respectively, meaning that (on average) an individual gold atom is heavier than an individual platinum atom.
At the same time, the ...
2
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0answers
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why lawrencium is placed in f-block elements although its last electron enters in 6d-subshell?
The electronic configuration of lawrencium ($\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,...
2
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1answer
333 views
Trend in atomic volume across a period [closed]
"Atomic volume decreases along a period, reaches a minimum at the middle, and then increases for the rest of the period"
Why does the atomic volume, along a period, initially decrease, ...
3
votes
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 ...
1
vote
1answer
569 views
What is the structure of CF3 radical? [duplicate]
In the class, I was told that $\ce{H3C^.}$ has a trigonal planar structure with the unpaired electron in $\mathrm{2p_z}$ orbital. But $\ce{H3C -}$ has a trigonal pyramidal structure.
But why does ...
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0answers
63 views
Why does solubility of Carbonate salts of Alkali metals in water increase down the group?
Carbonate salts have a very large anion so hydration energy should dominate over lattice energy. Since hydration energy is inversely proportional to radius of ion, I would expect Lithium to release ...
3
votes
1answer
7k views
What is the lattice structure of manganese?
A transition element is defined as the one which has incompletely filled d orbital in its ground state or in any one of its oxidation state. Zinc , cadmium and mercury are not typical transition ...
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0answers
63 views
Why doesn't core charge increase down a group? [closed]
Atomic radius increases down a group because the electrons feel a lesser attraction to the positive nucleus (due to shielding from inner shells). Why then, doesn't core charge decrease seeing as core ...
1
vote
1answer
12k views
What is the reason for the different solubility of silver halides in ammonia?
According to my knowledge, I know that $\ce{AgCl}$ dissolves in dilute ammonia, $\ce{AgBr}$ dissolves in concentrated ammonia and $\ce{AgI}$ does not dissolve even with concentrated ammonia.
What is ...
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0answers
260 views
Why is the strontium ion smaller than the potassium ion? [closed]
The ionic radius of the $\ce{Sr^2+}$ ion is $\mathrm{132\,pm}$, while the ionic radius of the $\ce{K^+}$ ion is $\mathrm{152\,pm}$. Why is this the case? I would have thought that since $\ce{K^+}$ has ...
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2answers
2k views
How to tell which species has the highest ionization energy?
I am preparing for my final exam, and I am very confused about ionization energy. An example question would be:
Between the species $\ce{Ne, Na+, Mg^2+, Ar, K+, $\&$~Ca^2+}$, which one has the ...
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1answer
174 views
Why is phosphorus trifluoride the strongest Lewis acid among the phosphorus trihalides?
I had read that for the trihalides of boron, boron trifluoride is the weakest Lewis acid due to backbonding. The order I had seen was -
$\ce{BI3 > BBr3 > BCl3 > BF3}\$
$$\ce{}$
$- order of ...
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1answer
48 views
Scale to be considered for comparing electronegativities of nitrogen and chlorine
The Pauling scale gives the $\chi$ values of $\ce{N}$ and $\ce{Cl}$ to be $3.04$ and $3.16,$ respectively, but the Allen scale gives the $\chi$ values of $\ce{N}$ and $\ce{Cl}$ to be $3.066$ and $2....
0
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1answer
244 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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1answer
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why is lithium oxide so different from water [closed]
Take water and replace hydrogens with the next element down in the periodic table, and you get a white solid, nothing like water.
https://en.wikipedia.org/wiki/Lithium_oxide
Lithium itself is very ...
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903 views
Why does the electron affinity increase become more exothermic down group 2 and group 5?
It is generally true that the electron affinity becomes less exothermic down a group, because of the increase in atomic radius.
There is a well-known exception that the electron affinity of Cl is ...
