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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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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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
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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 ...
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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+ ...
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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 ...
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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-...
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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
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2 answers
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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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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 &...
Scindus's user avatar
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1 answer
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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. ...
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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?
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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
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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 ...
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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 ...
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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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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 ...
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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
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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 ...
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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
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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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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
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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
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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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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
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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. $r_\ce{Li+}<r_\ce{Na+}<r_\ce{K+}$...
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6 votes
1 answer
267 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
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2 answers
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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 ...
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1 answer
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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 ...
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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 ...
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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 ...
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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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1 answer
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Why is copper a better conductor of electricity than calcium?

How would we compare the electrical conductivity between copper and calcium? I understand that electrical conductivity of a metal is dependent on the number of delocalized electrons for that metal. ...
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The melting and boiling point decreases down the group up to group 14 (not including transition metals), but the trend reverses from group 15. Why?

In groups 1, 2, 13 and 14, the melting and boiling point decreases down the group with a few exceptions. In group 15 the melting/boiling point increases up to Arsenic and then started decreasing. In ...
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What determines the kind of Bravais lattice structure (body-centred cubic, hexagonal, etc) a transition metal shows?

With the exception of Zn, Hg, Cd and Mn transition metals most transition metals have only one kind of lattice structure at room temperature. Another trend I noticed was that Groups 3 and 4 have ...
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1 answer
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Why does magnesium have a greater ionization energy than lithium?

I'm a high school student and I'm learning about ionization energy and atomic radius of elements. I want to compare the ionization energy of lithium and magnesium. Here is the information provided in ...
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Is Copernicium a transition metal? [duplicate]

Zinc, cadmium, mercury and copernicium belong to the group 12 of the periodic table. In my textbook , it is mentioned that zinc, cadmium and mercury are d-block elements, but not transition metals. ...
Pal's user avatar
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9 votes
2 answers
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Exchange energy of d6 configuration

In NCERT Chemistry book, it is given as: Exchange energy is responsible for the stabilization of energy state. Exchange energy is approximately proportional to the total number of possible pairs of ...
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2 votes
1 answer
655 views

Effect of d-orbital electron shielding on atomic radius

In a standard book it is given: "Atomic radius of Gallium is less than that of Aluminium. This can be understood from the variation in the inner core of the electronic configuration. The ...
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Relation between Ionization energy and reactivity

So I was learning about the periodic table where I came across the topic of ionization energy. As a general trend the Ionization energy decreases as we move down a group with a few exceptions such as ...
Nahul Alaguraj's user avatar
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Which oxidation states were used when Pauling developed his electronegativity scale?

Paulings electronegativity is a relative scale, based on the difference in electronegativity between X and Y, $\Delta EN = 0.102 \sqrt {\Delta}$, where $\Delta = (X-Y)_{measured}-(X-Y)_{theoretical}$ ...
Quantonium's user avatar
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1 answer
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Why do selenium , tellurium and polonium have more negative electron gain enthalpy than oxygen?

In my book(NCERT Chemistry Part I, Textbook for Class XI[1]) a list of values of electron gain enthalpies of various elements is given. According to that list, oxygen has less negative electron gain ...
ecneics's user avatar
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1 answer
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Do organopolonium compounds exist?

Analogues of alcohols exist for all the heavier Group 16 elements, namely sulfur, selenium, and tellurium. Would polonium also be able to form a "polonol" like $\ce{CH3PoH}$?
Bruh Moments's user avatar
3 votes
1 answer
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Why is strontium(II) ion bigger than krypton atom?

$\ce{Sr^2+}$ is exactly the same as $\ce{Kr}$, in terms of electrons and orbitals. The only difference between the two, is that $\ce{Sr^2+}$ has a couple of extra protons in the nucleus (and probably ...
peppa's user avatar
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1 answer
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Acidic character and anion stability across periods and groups of the periodic table [duplicate]

I understand that to compare relative acidity one must consider the stability of the conjugate bases. Across a period the electronegativity of an element increases. And that is for example why $\ce{HF}...
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Electron Affinity of Lead as compared to Bismuth

For "nitrogen family" and "carbon family" the trend goes that in a period, the electron affinity in case of group 15 is less than that of group 14. This is attributed to the half-...
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