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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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Why isn't the slope in atomic number vs calculated atomic radius graph same for different block elements?

This is a graph of atomic number vs calculated atomic radius for different block elements: Two questions: Why isn't the slope line same? why does the transition metals slope taper off to zero, ...
Coo's user avatar
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How atomic radii are decreasing across a period [duplicate]

I have been taught that atomic radius decreases across a period since the number of energy levels of an atom remains the same but the number of protons in the nucleus is increased and therefore the ...
Yara Try's user avatar
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Are Fajans rules relevant to melting and boiling points of alkali metal hydrides?

Among LiH, NaH, KH, RbH, CsH the one with the highest melting point is LiH, and it keeps on decreasing till CsH. The reason for this in my textbook is that the size of cations keeps on increasing down ...
Unlogical Chymist's user avatar
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1 answer
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Electron Affinity Trends in Period 2 [closed]

I'm new to this forum, but I had a question about electron affinity. In the second period, why do electron affinity trends feel so random? In this series, the first three terms made sense to me. ...
Schrödinger's Cat's user avatar
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2 answers
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I was told that Lithium and group 2 bicarbonates does not decompose on heating.Group 1 bicarbonates does decompose except lithium

But in some sources it was explained that stability of group 1 bicarbonates increases down the group.If it is true then how does lithium bicarbonate does not decompose ?.Can anyone please tell me ...
B. RITHISH's user avatar
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Upon what does the half life of a nuclide depend on? [duplicate]

Nuclide half-lives seem to be apparently random, except for the fact that heavier elements are typically radioactive and lighter ones stable. Is there any factor that can predict the half life of a ...
stickynotememo's user avatar
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Why aren't other elements with valence 6s electrons liquid like mercury?

I found out that mercury's 6s electrons undergo relativistic effects that make their pull to the nucleus greater, which makes it so that they can't bond with other atoms of mercury to form a solid. ...
ilikemath12783's user avatar
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Why is there anomalous trend in third ionization energy for Pr-Pm and Dy-Er?

It is not hard to observe the anomalously flat regions at Pr-Pm and Dy-Er in the trend of IE3 of lanthanides:, each described as the "first quarter" and "third quarter". Why is ...
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Can the relative reactivity of metals be explained by ionization energy and/or electronegativity?

I'm a 9th grade physical science teacher, and we're currently learning periodic trends. This is the first chemistry my students have learned. One of our labs for this unit has to do with the relative ...
Golden Eagle 1's user avatar
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1 answer
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How would you explain the general trend in melting point between Group 1 and Group 2 chlorides?

This question is based off of the attached chart. I notice how there's a general increase in melting point down group 2 chlorides and a general decrease (except for Lithium) down the group 1 chlorides....
Joe Dahl's user avatar
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Ionic radii of cations and anions

My textbook mentions that across a period from left to right, the ionic radius of atoms decreases. I'm a bit puzzled because negative ions in the same period have an extra shell. I get the part about ...
Andrés de Fonollosa's user avatar
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Does Cu+ have a greater ionic radius than Sr2+?

Although Strontium is in group 2, reducing the number of electrons as it becomes ionized makes it group 18, period 4 in terms of electrons. Therefore, ionized Strontium (Sr2+) is in the same period as ...
Woo Luke's user avatar
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2 answers
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Why aren't lanthanum, praseodymium, osmium, and mercury not on the same energy level?

The following question is from "The Official Guide to the HiSET Exam, Second Edition 2nd Edition", published by McGraw Hill, 2nd edition (March 25, 2016).2016 text, p. 75 (ISBN10: 1259640795)...
Sail2DeepBlue's user avatar
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Queries regarding Lanthanoid Contraction

Consider these two statements regarding lanthanoid contraction and their explanation as understood by me. Lanthanoid contraction is the greater than expected decrease in the atomic radii of the ...
TheCuriousOne's user avatar
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Are periods the horizontal numbers on the periodic table and groups the vertical numbers?

I am writing this post so that I can ensure for my upcoming SUC3U0 (Chemistry, Grade 11) course test of nomenclature is correct. It's a Review of my Grade 10 General Science Course. My teacher stated ...
Abdullah's user avatar
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Do the paired electrons of subshells' degenerate orbitals contribute to the total exchange energy?

For instance, in d7, there are 5 electrons with the same spin, and 2 electron with the opposite spin, meaning that there are only 3 unpaired electrons. So, which of these would be correct? (i) Total ...
Ayushi Kaushal's user avatar
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Some advice on inorganic textbook [duplicate]

I'd like to have some advice on Inorganic textbooks. I've already consulted some books (Kettle, Drago, Keiter, Cotton) and they are all very useful, but now I'm searching for a textbook which focuses ...
Chemistry.'s user avatar
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1 answer
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Why does Cr have higher melting point in the 4 period among the transition metal? [duplicate]

There is a lot of answer stating that the low enthalpy of atomisation in Cr is due to the reason of partially filled d orbital, thus having extra stability. This makes the orbital more attracted ...
Satyadarshi's user avatar
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3 answers
160 views

Why is there a non-uniformity in even the reasons that explain exceptions in the trends in chemistry? [closed]

I have been studying the periodic table and several properties of atoms like the Ionization Energy, Atomic Radii, Electron gain enthalpy, Electronegativity etc. Now, each property has somewhat of a &...
Bhavya Jain's user avatar
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Please explain the order of Lewis acidic strength in trichlorides of boron group

The order of decreasing Lewis acid character as per online sources is as follows: BCl3 > AlCl3 > GaCl3 > InCl3 Reason cited is: As we move down the group, the size of atom increases, and as a ...
Henri IV's user avatar
3 votes
4 answers
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Comparison of atomic radii of boron and beryllium

Let me write down a couple of facts and this will be easier for you to know the essence of the question. Radius of boron is smaller than beryllium. Ionization energy of boron is smaller than ...
Matt's user avatar
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Order of Second Ionisation Potential of C, N, O and F

Here's what I believe: The electronic configurations of the elements after losing 1 electron are: N+ -> 1s2 2s2 2p2 O+ -> 1s2 2s2 2p3 F+ -> 1s2 2s2 2p4 So, on losing 1 e- more, the value of ...
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Trend in formation enthalpy of metal fluorides

Please see below for the data I am referring to. I don't really understand why the trend in Cr ceases and reverses. I think I understand what the logic for WFn is - while the cost of forming Mn+ ...
Bartholomew696969's user avatar
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Why do the successive ionisation energies of Ni and Pt diverge?

The data I am referring to is below on the graph. The explanation I have found is that the 5d orbital of Pt is more diffuse than the 3d orbital of Ni, so is less sensitive to the increases in Zeff as ...
Bartholomew696969's user avatar
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Why is CrO3 an oxidising agent, but WO3 is not?

So apparently CrO3 can be used as an oxidising agent, but WO3 can not. I saw this on an assignment question which I will include below: I think the reason why W6+ is 6-coordinate and Cr6+ is 4-...
Bartholomew696969's user avatar
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2 answers
216 views

Why ionic radius increases with negative charge?

Here's my understanding: An ion with a negative charge has gained electrons. Hence the negative charge. With a greater negative charge, there should be more attraction towards the positive charge. As ...
Quin Gardiner Bax's user avatar
2 votes
2 answers
285 views

How did Mendeleev improve on the Newland's table?

I understand that John Newland’s law of octaves was ridiculed by the scientific community as his table failed to work past calcium. I'm trying to understand how Mendeleev’s table improved on this. On ...
Quin Gardiner Bax's user avatar
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2 answers
116 views

Is the periodic table ordered by bonded atoms and does that change the electron configurations and ordering? [closed]

In my book (Mortimer, The Basic Knowledge of Chemistry) the electron structure of the elements is introduced, there the relative energies of the atomic orbitals are shown: 1s < 2s < 2p < 3s &...
iwab's user avatar
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Lower melting points of zinc, cadmium and mercury

I am aware of the fact that d-block elements like zinc, cadmium and mercury have lower melting points than other d-block elements. Also I am aware that these three metals have a fully filled d shell. ...
Shashaank's user avatar
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Why middle elements of transition series show more number of oxidation states [duplicate]

Why do the elements in the middle of the transition series show more number of common oxidation states than others?
Shub's user avatar
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2 answers
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Why does the rate of change of atomic radius in the second period change so drastically?

I was reading in my textbook Chemistry Part I, Textbook for Class XI by NCERT, ed. January 2021 that: The atomic size generally decreases a period across as illustrated in Fig. 3.4 (a) for the ...
archthegreat's user avatar
3 votes
2 answers
2k views

Reason for exceptions in I.E. trend in group 13

In general, we would expect IE to decrease down a group. This is because atomic radius increases $\implies$ valence electrons are further from nucleus $\implies$ less effective nuclear attraction on ...
AVS's user avatar
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Trends in atomic radii across a period

I am a 12th grader. Recently, while revising the Periodic Table, I came across the statement: As the effective nuclear charge increases across a period, the atomic radius of the elements decreases on ...
ChaturLomdi's user avatar
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2 answers
773 views

Why ionization energy of Thallium is higher than that of Indium?

I just normally calculated the effective nuclear charge (Zeff) for thallium and Indium from Slater's law, and I found it same for both! That is 5.(If you want calculation for answering or correcting ...
Shinchan Nohara's user avatar
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2 answers
6k views

Why is effective nuclear charge said to be decreased down the group, but the Zeff calculated is increased down the groups instead?

Some textbook write that effective nuclear charge is constant when gping down the group,while some write that the effective nuclear charge decrease down the group So which statement is true? I try to ...
Pck Tsp's user avatar
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1 answer
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Confusion regarding 1st and 2nd electron gain enthalpy

$\ce{O}$ has the 1st electron gain enthalpy $\pu{-141 kJ mol-1}$. $-ve$ value implies that energy is released when electron is added to an isolated atom. This also means that if $\pu{141 kJ}$ energy ...
Eisenstein's user avatar
1 vote
1 answer
99 views

Reason of being 2nd ionization energy

Why is the second ionization energy always greater than the first? By shielding effect, it shouldn't have been true. Let's take $\ce{Mg}$ and $\ce{Mg^+}$ for example. Effective nuclear charge(ENC) for ...
madness's user avatar
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Extent of Melting of Bonds or Intermolecular Forces

I'm currently having a revisit on the subject of periodicity of the periodic table, and I came across an issue that is kind of bugging me. If we take a look at the melting and boiling point trends of ...
JY _Decipherer_'s user avatar
-5 votes
1 answer
86 views

Can halogens show -3 or -5 or -7 oxidation state. Why? [closed]

I mean can we think it like if the electrons get excited into the d orbitals and because there are now more than one unpaired electron, why does it only loose them and why don't they accept more than ...
Ryn's user avatar
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-4 votes
1 answer
79 views

Doubt regarding trends in modern periodic table [closed]

We know that atomic radius decreases along a period and increases along a group. (Same goes for metallic character) But if we take 2 elements A & B(A is at somewhere in the top and left in ...
Nipun Kulshreshtha's user avatar
-3 votes
1 answer
802 views

Why are certain gases with higher molar masses less dense than the ones that have a lower one?

Neon, despite having a larger molar mass than nitrogen, oxygen and fluorine, is less dense than all of them. This also goes that fluorine (again) and chlorine are both denser than argon, even though ...
Bruh Moments's user avatar
1 vote
1 answer
404 views

Why is reaction of Li less vigorous than that of Na although the former has a more negative SRP value?

My textbooks says: It may be noted that although lithium has most negative E0 value (Table 10.1), its reaction with water is less vigorous than that of sodium which has the least negative E0 value ...
star's user avatar
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2 votes
3 answers
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Why an atom is more stable when only sublevels s and p are full?

Supposedly when explaining electronegativity and stability of an element, they tell you that it is more stable if the last level is full. That works up to the third period, but after transition ...
Curious student's user avatar
1 vote
1 answer
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Why are hydrated lithium ions' radii larger than hydrated sodium ions' radii?

Why are hydrated lithium ions' radii larger than hydrated sodium ions' radii i.e. $r_\ce{Li+(aq)}>r_\ce{Na+(aq)}$? If ionic radii increase down the group i.e. $r_\ce{Li+}<r_\ce{Na+}<r_\ce{K+}$...
user avatar
6 votes
1 answer
272 views

Is there a canonical variable for period and group?

For example, "Z" is the standard symbol for atomic number. I'm writing a manuscript that uses the group and period of elements within some equations, and so far I'm just denoting them as $G_{...
AmphotericLewisAcid's user avatar
1 vote
2 answers
231 views

The oxidation number of N and Cl in NOClO4 ​

My doubt is not about the solution itself, actually I was able to find the solution myself. We could split NOClO4 as (NO+) + (ClO4-) and then proceed, but here I "knew" this split. Is there ...
Fr0zen's user avatar
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2 votes
1 answer
365 views

Does fluorine have 5 or 7 active valence electrons?

In a paper on chemical periodicities of elements, Cao et al. show the number of valence electrons in a periodic table (https://doi.org/10.1515/pac-2019-0901). Apart from Boron and Aluminum shown as ...
Karsten's user avatar
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1 answer
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How to know the group number from the ionization energy?

The successive ionization energy of the first four electrons of a representative element are $\pu{738.1 kJ/mol}$, $\pu{1450 kJ/mol}$, $\pu{7730 kJ/mol}$ and $\pu{10500 kJ/mol}$. Characterize the ...
An Alien's user avatar
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0 votes
3 answers
258 views

Do Ions with less stability have less energy of ionization than those who are stable?

Problem. I've come up with the strange example of the third energy of ionization of both $\pu{Mg}$ and $\pu{Al}$, the standard logic that is to be applied on any problem of "which element has ...
Acyex's user avatar
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3 votes
3 answers
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Which atom is the smallest atom?

Is hydrogen or helium the smallest atom? My teacher said that the smallest atom is the helium atom, but I think that the smallest atom is the hydrogen atom. It has a single electron and a single ...
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