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 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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Bond Energy in P-O , S-O , Cl-O

My text says that Bond energy between P-O , S-O , Cl-O follows the trend P-O < S-O < Cl-O. But I think it should be a reverse of what's given because more the electronegativity difference ...
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How well do d-block electrons actually shield?

I've been using 'Chemical Structure and Reactivity: An integrated approach' by James Keeler and Peter Wothers to study periodicity, among other sources. However, there seem to be some commonly ...
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Why color of alkali metal peroxides, superoxides and ozonides deepens down the group?

This is basically a continuation of the question-"Why is potassium monoxide (K2O) coloured?" I knew that color of alkali metal oxides deepens down the group: Lithium oxide ($\ce{Li2O}$) is the ...
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1answer
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Why several of isomers of octane such as 2,3-dimethylhexane and 2,4-dimethylhexane doesn't have a value for melting point from any databases?

This is a very rough data (as shown below) I have collected from CRC Handbook of Chemistry and Physics 93rd edition in black and ChemSpider in blue. As you can see, I am not quite done, but I was ...
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1answer
916 views

Is using melting/boiling point good to measure volatility?

I wanted to figure out a way to compare volatility in organic compounds, so I read on many forums on the differing ways to measure volatility, which included enthalpy of vaporization and melting/...
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What are the ideal pair of (everyday) elements to pair in a thermocouple

I want to create a thermocouple (to carry out experiments on thermoelectricity). I want to use the pair of everyday* elements (e.g $\ce{CuO}$ and $\ce{Al}$ wires) to create the thermocouple. The ...
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Why the radius of noble gases is more than the halogens or the previous groups?

Noble gases have a larger radius than the halogens. Sometimes it is greater than the radius of group I elements. Why it is like that? When we talk about radius of noble gases what type of radius ...
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Random order of melting points of group 2 elements

Compare the melting points of $\ce{BeF2, MgF2, CaF2, SrF2, BaF2}$. Actual order is $\ce{ BeF2 > CaF2 > SrF2 > BaF2 > MgF2}$. I have worked out the following things while comparing ...
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Periodic trends on half cell potentials

In a practice examination that I'm using to study for my upcoming midterm, one of the questions asks to choose three elements from a row of the periodic table and to give the order of the increasing ...
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Oxidation state of Halogens

So the question is which is the most common oxidation state of halogens and I have to justify my answer. Is my following thought correct? Do I have to add something? The most common oxidation state ...
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Boiling Point trend

Why does group 13 and 14 show reverse the trend of boiling point? In other groups, boiling point increases down the group but here it decreases.
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1answer
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Pattern to determine the maximum ionic charge for transition elements?

According to my textbook, main group elements follow a simple pattern when determining their maximum ionic charge. The maximum cationic charge is always equivalent to their main group number (group ...
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1answer
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Reducing character of group 15 hydrides

It was given in my text book that reducing character of group 15 hydrides increases down the group. I am a bit confused about this. For $\ce{NH3}$ this is fine as I assume that: $$\ce{NH3 -> N + H^...
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Why do heavier transition metals show higher oxidation states?

In p-block elements, higher oxidation states are less stable down the group due to the inert pair effect. This is not the case for transition metals. Why do heavier transition metals show higher ...
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Atomization enthalpies of transition elements

So, my book says that transition elements have higher enthalpies of atomization than other elements (say s- or p- block) because of stronger metallic bonding, primarily due to large number of unpaired ...
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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 ...
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Why is the first ionisation energy of a sodium cation bigger than that of a neon atom?

I understand that the 1st ionization energy gets bigger for elements along a period from left to right and along a group from down to up. But why is the 1st ionization energy of $\ce{Na+}$ bigger ...
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Trend of second Electron Affinity for N,O,F,P,S,Cl

I am aware of the definition of electron affinity and electron gain enthalpy (EGE). N has positive EGE1, and EA of P,S,Cl is more than N,O,F respectively. I want to arrange them in order of their EA2 ...
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Why does oxygen in OH have an oxidation state of 2-?

I am watching videos on Khan Academy in order to go over redox reactions (a really weak area for me.) In Sal's video, "Oxidation state trends in periodic table" at 7:10, he says: If you had to ...
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Why magnesium has the lowest melting and boiling point in its group? [duplicate]

It is written in the third point ( shown in the picture) that presence of d orbitals results in stronger metallic bond. 1) We check the strength of metallic bonding to compare the melting and boiling ...
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Hydrolysis products of chlorides of group 15

$\ce{NCl3}$ on hydrolysis produces $\ce{NH4OH}$ and $\ce{HOCl}$. $\ce{PCl_3}$ when hydrolyzed produces $\ce{P(OH)3}$ i.e. $\ce{H3PO3}$. $\ce{AsCl_3}$ when hydrolyzed produces $\ce{As(OH)3}$. ...
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Why is the melting point of hydrogen iodide larger than that of hydrogen fluoride?

Compare the melting points of hydrogen fluoride (HF) and hydrogen iodide (HI). I know the following things: $\ce{HF}$ melts at $189.6~\mathrm{K}$ and $\ce{HI}$ at $222.35~\mathrm{K}$. There are a ...
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Why is the boiling point of stibane higher than that of ammonia?

I recently came across the fact that the boiling point of $\ce{SbH3}$ (stibane) is greater than that of $\ce{NH3}$ (ammonia). I was expecting $\ce{NH3}$ to have a greater boiling point as a ...
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1answer
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On a periodic table it shows that Zn and Cd and Hg all have 0 electron affinity. Why is that?

Question On a periodic table it shows that Zn and Cd and Hg all have 0 electron affinity. Why is that? What I've noticed I've noticed that these three elements are the end of the D orbital and they ...
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Why are alkali salts so soluble?

There's a certain solubility rule stating all carbonates, phosphates and hydroxides are insoluble unless mixed with hydroxides or alkali metals. Why is this? What makes the alkali metals so special?
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How to determine the valence electrons of D-block elements in their mono atomic form?

For s and p block we can determine the valence electrons easily,but what about d-block elements. How to determine their valence electrons?
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Finding electron configuration by following the Aufbau principle

In the question, "Electron Configuration of Tellurium", there is mention of the 'follow yellow brick road' method of finding electron configuration. What I'd learned in the past was to find the ...
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1answer
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Melting Point Trend For Non Metals?

I noticed that the melting point for non metals decreases across a period (i.e. melting point of nitrogen is higher than oxygen, oxygen's is higher than fluorine, so on). It is significantly more ...
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How to explain the periodic trends in boiling points in groups?

Observing the trend of boiling points of the compounds listed, choose the appropriate terms to fit into the blanks: \begin{array}{lr} \text{Compound}& \text{boiling point}\\\hline \ce{H2Te} &...
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Trend in atomic radius for noble gases

In an exam, we were given the following graph and asked to explain why the slope of the change in r vs. Z changes dramatically at a point along the curve. I understand that the d block causes the ...
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Why hydrogen disulfide and not hydrogen persulfide?

Recently, I was checking on this question and I was thinking of the name of the compound $\ce{FeS2}$. Later I checked the name in the answer to be iron disulfide. I found the following statement in ...
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1answer
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Reason for decreased boiling point of hexafluoroisoproponal?

Ethanol and isopropyl alcohol have boiling points 78.37 °C and 82.6 °C respectively. The increase in the boiling point is obvious due to increase in carbon chain length which resulted in increase in ...
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Meaning of charges in a group?

In my class, my professor said that since hydrogen is in group one, it has a charge of 1+. Does this refer to its ionic charge or to its oxidation state?
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As we go down a fluoride-alkali metal series, why doesn't the boiling point decrease?

As you can see from the graph below, as we go down the blue fluoride-alkali metal series (alkali metal ion is varied from Lithium to Rubidium, which is represented by an increase in ionic mass on the ...
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Which hydrogen halides react with group 14 oxides?

$$\ce{6HF +SiO2->H2SiF6 +2H2O}$$ $\ce{HF}$ reacts with $\ce{SiO2}$ to form $\ce{H2SiF6}$. Do other hydrogen halides like $\ce{HCl}$ and $\ce{HBr}$ react with group 14 oxides in the same way?
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Shielding effect- specifically defined?

In all the sites I have searched, shielding effect has been defined as the reduction of the nuclear attraction upon the outer electron/electrons, due to the core electrons that repulse the outer ...
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1answer
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If fluorine has a lower electron affinity than chlorine, why does it have a higher ionization energy?

I have read that fluorine has a lower electron affinity than chlorine despite its lower atomic radius because its electron cloud is extremely dense. If this is the case, shouldn't the ionization ...
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Will O or S accept an electron more easily?

O has more electronegativity than S but S has more Electron Gain enthalpy than O. How do we decide, which one pulls the electron more easily? In other words, Electron gain enthalpy dominates or ...
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Why is the ionic radius of Al(3+) smaller than that of Li+?

I was examining the ionic radii of some ions from this site for a school assignment. I noticed a weird anomaly in the ionic radius of $\ce{Li+}$ as compared to that of $\ce{Al}^{3+}$. The ionic ...
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1answer
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Periodic table and p block elements

I have two questions: It's said that in p block there's gradation in physical and chemical properties of elements. What is meant by this statement? Why are the different blocks named s, p, d and f?
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Why does cobalt have a higher atomic mass than nickel?

I understand that this deviation from the general trend of increasing atomic number and atomic mass is because cobalt's isotopes tend to have more neutrons than nickel's. Why is that the case? How ...
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Which has the largest bond angle between water, oxygen difluoride and dichlorine oxide?

Which one out of $\ce{H2O}, \ce{Cl2O}, \&\ \ce{F2O}$ will have largest bond angle? I think it should be $\ce{H2O}$ because oxygen is most electronegative in this case so electrons will be more ...
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About ionic bonds (and ionic compounds) [closed]

I have a few questions: All ionic bond occurs between a metal and a non-metal. Is this true? In the definition of metal and/or non-metal are the metaloids included? In the definition of non-metal are ...
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Why does electronegativity generally increase across a period? [duplicate]

I've been doing some research and the only answer I seem to be getting is that the increase of protons means electrons are more attracted to the atom. I thought though it was because as you go ...
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Why is there a discrepancy among sources on the atomic radius of some elements?

My book says the atomic radius of gallium is less than that of aluminium, but I found out different atomic sizes on different sites. For example, this says gallium is 136 pm and aluminium is 118 pm, ...
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why are mercury gas and tungsten filament used in electric bulbs instead of fluorine which has higher electron affinity?

Fluorine has greater electron affinity than mercury or tungsten and hence fluorine could have been in electric bulbs.Because it can attract electrons easily than the metals which mostly repel extra ...
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Alkali metal hydrides

I know that stability of alkali metal hydrides decreases down the group,Hence the lowest member in the group easily breaks into its cation but does this easiness of breaking into cation has any ...
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Melting points of alkali metal halides

The correct order of melting point of alkali metal halides is: $\ce{MF}>\ce{MCl}>\ce{MBr}>\ce{MI}$ $\ce{MI}>\ce{MBr}>\ce{MCl}>\ce{MF}$ $\ce{MCl}>\ce{MF}>\ce{MBr}>\ce{MI}$ $\...
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Which is the most reactive element in the periodic table? [duplicate]

Which is the most reactive element in the periodic table? Is it francium, caesium, lithium or fluorine?