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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1answer
13k 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
6k 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
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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
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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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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
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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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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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332 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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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 ...
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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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2answers
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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
553 views

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
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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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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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943 views

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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3answers
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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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1answer
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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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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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1answer
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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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277 views

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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820 views

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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2answers
162 views

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?