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 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 ...
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2answers
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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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3answers
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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.
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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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1answer
1k 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 ...
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880 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 ionization ...
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246 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 ...
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1answer
430 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 (...
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1answer
874 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 "...
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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 ...
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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 ...
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229 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 ...
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770 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 ...
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1answer
6k 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 ...
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1answer
7k 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 ...
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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 ...
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1answer
1k 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 ...
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2answers
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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 ...
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1answer
3k 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, ...
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1answer
1k views

Trends in ionization energy in the second period [closed]

Question Which element among the following has the highest ionisation energy: fluorine, oxygen, neon. I know that all these elements belong to period 2 and ionisation energy increases from left ...
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1answer
7k views

Boiling point trend in group 13

My Theory: Since atomic mass increases down the group, the van der Waal's forces should also operate to a greater extent, thereby making it difficult to change the phase of the substance. Hence, ...
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1answer
633 views

Why does cobalt have no negative charge?

I would like to know why cobalt cannot have a negative charge (or at least why a negative charge for cobalt isn't typical). I am not sure where I have gone wrong in my reasoning. The electronic ...
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2k views

Why does hydration of ions depend on their charge to area ratio?

The following is written in my book Concise Inorganic Chemistry by J. D. Lee. Hydration energy, hydrated radius and hydration number of a particular ion depends upon charge per unit area. Hence their ...
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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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Abnormal ionisation energy trend: Group 13 and 14

I was going through some ionisation energy data, where I came across the following: Ionisation energy order for Group 13 and 14: B > Al ≈ Ga > In < Tl C > Si > Ge > Sn < Pb What could be the ...
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1answer
3k views

Order of second ionization energy for cations

Why is the correct order of second ionisation potential of $\ce{Li , Be , B , C }$ such as: $\ce{Be} <\ce C <\ce B <\ce{Li} $? I understand that $\ce{Li+}$ has a stable inert gas electronic ...
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817 views

Why doesn't D block contraction affect the other P block groups 14 15 16 etc

Usually we come across anomalies in the trends of periodic properties for example the size [Atomic radius value from Raymond Chang Chemistry 9th Edition] of Gallium (135 pm) is smaller than Aluminium (...
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Comparision of the Ionisation Energy Change of the alkali metals and noble gases?

Currently I compare the ionisation energys of the alkali metals: Li: $\pu{0.52 eV}$ Na: $\pu{0.50 eV}$ K: $\pu{0.42 eV}$ Where only a slight drop (appr. remain constant) occurs. This ionisation ...
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1answer
2k views

Electronegativity trends: Is it more important to prioritize families or periods? [closed]

I know that an atom that an atom is more electronegative as it moves up a group or right on a period (in terms of the periodic table). So if you have two atom that is diagonally across from each ...
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541 views

Rationalising the trend of standard electrode potentials between the +II and +III oxidation state of first-row transition metals

Trends in standard electrode potentials of d block elements: An examination ofthe $E^0 (\ce{M^3+}/\ce{M^2+})$ values (Table 8.2) shows the varying trends. The low value for Sc reflects the ...
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109 views

Quickly deduce block (s, p, d …) from atomic number [closed]

A question from previous year papers of IIT JEE. There's not enough time to write the electronic configuration in the exam. Please suggest a quick, objective approach.
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1answer
809 views

Why are group 1 elements so low in density?

I was studying the s-block elements and found that they extremely low in density. Lithium is said to be the least dense solid in the entire periodic table and their Cohesive Energies are also very low....
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Confusion between electronegativity and electron affinity

Electronegativity is a chemical property that says how well an atom can attract electrons towards itself. The electron affinity of an atom or molecule is defined as the amount of energy released ...
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Non existence of B3+ in solution [closed]

I read that B3+ ions do not exist in aqueous solution, because hydration energy cannot compensate for the sum of first three ionisation energies. This leads me to the following questions: If boron (...
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2answers
3k views

Which element has larger atomic radius — beryllium or xenon?

I say that xenon radius is smaller comparing to beryllium, but my friend says otherwise. What I think is that xenon is down in periodic table comparing to beryllium (3 periods down) and it's far ...
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1answer
82 views

Do the spins of outer orbitals block measurement of spin of inner orbitals?

Do the outermost s1 and s2 electrons block an outside observer from measuring the larger inner group orbitals for elements heavier than Nitrogen (for instance, would Chromium's 4s1 electron or ...
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12k views

Thermal stability of alkali metal hydrides and carbonates

Why is it that thermal stability of alkali metal hydrides decreases down the group, but for carbonates, it increases? I used Fajan's rule to check for ionic character but somehow this is only ...
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1answer
5k views

Difference between Oxidation Potential and Ionization Potential [closed]

Ionization potential indicates a substance's tendency to loose electron and become a positive ion. So, a substance becomes ion more easily if it has a lower ionization potential (lower energy needed ...
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Acidity/basicity of oxides across the periodic table [duplicate]

Recently while self-studying my chemistry book, it dawned on me that metals form basic oxides and nonmetals forma acidic oxides. Why is this?
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1answer
11k 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 ...
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1answer
1k views

On the periodic table: Why are groups of elements organized by 'letter' [duplicate]

Why are the groups of elements on the periodic table organized into areas represented by the letters s,p,d,f,g, and h? What does this mean?
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108 views

Relative orbital energies of Mn and Ni

In this MO diagram, why are the atomic Mn $3d$ orbitals higher in energy than the Ni $3d$ orbitals?
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Deviation in bond angles (from standard $109°28'$ ) in hydrides of group 15 [duplicate]

Here are the approximate bond angles for first three members of group15. $\ce{NH3}$: $107°$ $\ce{PH3}$: $94°$ $\ce{AsH3}$: $92°$ As we move down the group the bond angles approach towards $90°$. ...
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What proof is there that the “Island of Stability” exists?

Often I see people talking about an "Island of Stability" existing for super-heavy elements on the periodic table, but I don't see any reason to thinks this exists? Surely the heavier you go the more ...
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Trends in Slater's constant

I am aware of the various Slater rules to calculate the effective nuclear charge, $Z_\mathrm{eff}$ However, how can I decide the order in which the orbitals 2s, 3s, 3d, 3p, 4d, and 4f stand when ...
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1answer
928 views

Last electron of a transition element

The electronic configuration of nickel is Ni: [Ar] $3d^84s^2$ Here, while writing the configuration, we fill the 3d after 4s.Hence the 28th electron enters the d orbital. But $\ce{Ni+}$: [Ar] $...
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1answer
190 views

Why don't elements having the same valency as Carbon bond so readily?

I haven't been in touch with Chemistry as a subject of study for several years now. Still- if I remember correctly, Si, Ge, Sn, Pb all have same number of electrons as Carbon in their outer orbits. ...
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1answer
311 views

Good collection of images showing periodicity of the Table?

Mendeleev's recognition of the periodicity of atomic trends was a milestone of human understanding, the detection of a pattern in what had appeared to be chaotic data. I think the significance and ...
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1answer
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Why the ionization energy of Au is more than that of Cu?

As we go down the group from 3d to 5 d, size increases. Vanderwaal radius of Cu and Au is 140pm and 166pm respectively. Since Cu is smaller in size, ionization energy of Cu must be greater. Then ...
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Comparing electronegativities of aluminium and gallium

If I were to compare the electronegativities of Al and Ga, shouldn't I be saying that the electronegativity of elements (in general) decreases down the group, I say this by thinking of the position of ...