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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Is Copernicium a transition metal?

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. ...
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Why indium and thallium doesn't react with alkali solution? [closed]

It is given in my book that ' In Boron family, only Aluminum and Gallium reacts with alkali solution and not Indium and Thallium' What makes indium and thallium unreactive to alkali solution?
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Palladium and Nickel [closed]

The general trend of Ionization Energy is that it decreases down a Group in the Periodic Table. Why don't the Group 10 elements(Nickel, Palladium and Platinum respectively) follow the same trend? (I.E ...
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356 views

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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1answer
95 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 ...
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59 views

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 $\Delta = (X-Y)_{measured}-(X-Y)_{theoretical}$ ...
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223 views

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 ...
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100 views

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 $\ce{CH3PoH}$?
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91 views

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 ...
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43 views

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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S(p)-C(p) vs. O(p)-C(p) overlap

In Grossman, The Art of Writing Reasonable Organic Reaction Mechanisms, he provides the following explanation. The question asks to explain why the difference in pKa values between PhSH and EtSH is ...
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Is there an enolate equivalent for enamines?

I'm learning that enolates are stronger than enamines are stronger than enols in terms of general nucleophilicity. Makes sense. But what I can't find any explanation for online is why the trend ...
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Why is the increase in covalent radius from As to Bi not as big as from N to P?

The following is the radius of Group $15$ elements: $$\begin{array}{c|c} \hline \text{Element} & \text{Covalent Radius }(\pu{pm}) \\ \hline \ce{N} &75 \\ \ce{P} &110 \\ \ce{As} &...
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Color of Flame Test for Alkali Metals

Lithium is known to have the highest ionization energy among Group 1 elements. Also, characteristic colours in the flame test arise due to the excitation and de-excitation of electrons. Then why ...
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Why is magnesium sulfate more soluble in water than that of strontium and calcium sulfates?

Magnesium sulfate is soluble in water. Its solubility is $\pu{26.9 g}/\pu{100 mL}$ at $\pu{0 ^\circ C}$ $(\pu{35.1 g}/\pu{100 mL}$ at $\pu{20 ^\circ C})$.[1] However, both calcium sulfate $(\pu{0.21 g}...
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Out of KCl, CaCl2, MgCl2, NaCl, which causes the greatest corrosion rate of iron and why?

I know that salts act as an electrolyte in a redox process and rusting of iron, where iron loses electrons and oxidizes, and oxygen gains electrons and reduces. I did an experiment with KCl, NaCl, ...
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Predict the valence configuration of this element using the first five ionization energies [closed]

If the first five ionization energies of an element are, respectively: $\pu{1.09 kJ/mol}$, $\pu{2.35 kJ/mol}$, $\pu{4.62 kJ/mol}$, $\pu{6.22 kJ/mol}$ and $\pu{37.83 kJ/mol}$, to which group of the ...
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68 views

Why does the ionization enthalpy of elements across a period not follow a regular pattern while the atomic size always decreases?

First of all, I would like to mention that I am only talking about elements that aren't from the d or f blocks. In order to further elaborate on my question, I would like to take the third period as ...
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62 views

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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167 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 ...
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888 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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61 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 ...
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48 views

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 ...
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152 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 ...
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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 ...
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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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56 views

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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738 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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490 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. ...
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136 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 ...
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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,...
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789 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, ...
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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 ...
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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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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 ...
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473 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 ...
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432 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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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 ...
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416 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 ...
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144 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....
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329 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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529 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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99 views

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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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 ...
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460 views

Why aren't Boron and Aluminium assigned to group 3 of periodic table? What determines the group? [closed]

I've been curious about this 3D representation of the periodic table "Mendeleev's Flower" and was trying to study it, wondering if it reveals any regularities that are not obvious from classic ...
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1answer
333 views

Why is the first energy of ionization of oxygen lesser than that of nitrogen? [duplicate]

The following question arises from a question I found in my book. Experimentally it has been determined that the value of the first energy of ionization of oxygen is lesser than the first energy ...
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121 views

Is strontium more metallic than sodium? If yes then why?

I got an MCQ in my examination, "Which one of the following is more metallic?" and the options were Sr, Na, Be or Aluminium. I know that sodium is more metallic than Be or Al but my mind stuck on ...
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Why Zn has highest ionisation enthalpy in 3d series?

Zn which has the highest ionisation enthalpy in 3d series.The reason given in my textbook is: The value of zinc is higher because it represent ionisation from 4s level. This is not correct because ...

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