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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What do you mean by “periodic” in the periodic table? [closed]

Modern periodic law states: “The physical and chemical properties of the elements are periodic functions of their atomic numbers”. But I don't think this is so! (Forgive me for my stupidity. But ...
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Relation between reactivity series and electrochemical series [closed]

I have already read answers to the following questions: Reactivity series of metals What is the difference between reactivity series and electrochemical series? But I didn't get what I wanted. When ...
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Stability of halogen oxides [closed]

I was studying periodic properties, p-block and came to the following line:- The higher oxides of halogens tend to be more stable than lower ones Why is it so? Explain.
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886 views

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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Electronegativity of heavier elements of Group 15

While reading about p-block I got to know that in Group 15 elements electronegativity value decrease down the group but amongst the heavier elements difference is not that much pronounced. I ...
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How ion size/electronegativity influences strength of an acid

My prof was explaining how we can use the structure of acids and bases to rationalize relative strengths (ie: acid X is stronger than acid Y because ...). He then went on to explain how when ...
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3answers
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Is acidic character related to reducing power?

My book says that the acidic character of halogen acids increases on going down the group because the bond strength decreases, making it easier to release the $\ce{H+}$. But I also know that $\ce{HI}$...
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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 ...
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Melting and boiling points of transition elements

The melting and boiling points of transition elements increases from scandium ($1530~\mathrm{^\circ C}$) to vanadium ($1917~\mathrm{^\circ C}$). They increase because as we go across the group, we ...
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Can you calculate the properties of a substance based solely on its atomic properties?

I'm trying to write some software that I can use to determine, roughly, what the physical properties of a pure substance are. I know I could just use a database of the known properties of each element,...
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Ionization enthalpy for group 13 elements

The ionization enthalpy for elements along a group generally reduces. But there is an exception for group 13 elements and the order is not uniform. The order is: B>Tl>Ga>Al>In According to ...
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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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Atomic radii and why does it decrease in a period [closed]

Why do atomic radii decreases as you move from left to right across a period
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Why does Calcium have a higher ionization energy than Aluminium?

Given their places on the periodic table I'd assume Aluminium has a higher ionization energy, because it has fewer energy levels, and is on a "righter" row on the periodic table, but in reality it is ...
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Effective nuclear charge and Ionization energy

A common reason given on why 3rd ionization energy > 2nd > 1st is because of increasing effective nuclear charge. As per my book $Z_\mathrm{eff}$ = Atomic number $-$ Number of inner electrons. Now ...
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How would one determine an element simply by looking at its binding energy?

I am self studying MIT OCW chemistry 5.111 2014, one of the lecture questions states the following: Consider a neutral atom with 8 distinct electron binding energies: −14 eV, −28 eV, −94 eV, −218 ...
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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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Electron affinities of the chalcogens and halogens

Here are the electron affinities of the 16th and 17th groups. The general trend for electron affinity down the group is that it decreases because of the increase in atomic radius.The exception of $\...
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Standard Reduction Potentials and Electropositivity

I was looking through a table of standard reduction potentials and the trend seemed like it correlated with electropositivity. Is it reasonable to qualitatively compare two metals to see which has a ...
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Why does the emission wavelength of sodium appear to be an exception despite the trend for ionisation enthalpies among alkali metals?

The wavelengths for emissions in the visible region for Group 1 elements is as follows: $$ \begin{array}{lc} \hline \text{Element} & λ/\pu{nm} \\ \hline \ce{Li} & 670.8 \\ \ce{Na} & 589.2 ...
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Why is fluorine a oxidising agent?

An Oxidizing agent pulls the electron cloud of the substance being oxidized towards itself, for example: $$\ce{F2 + 2 X- → 2F^- + X2}\qquad (\ce{X} = \ce{Cl}, \ce{Br}, \ce{I})$$ We also know that ...
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Why is periodicity seen in these certain properties?

I missed my lesson on periodicity so had to teach myself, and have always forgotten to ask my teacher to explain to me why these trends are seen, which, unfortunately, the textbooks don't. Density: ...
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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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Why is lithium the most reducing alkali metal, and not caesium?

Caesium has a larger size, and the effective nuclear charge that the valence electron experiences will be far less compared to that of lithium's, right? But lithium is still considered the strongest ...
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Why does screening effect decrease due to d-orbital?

In 13th group, atomic radius increases from boron to aluminium. From aluminium to gallium, atomic radii decreases. From gallium to indium, atomic radii increases. And from indium to thallium, atomic ...
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Variation in atomic radii of elements in different blocks?

If we look at the values for the atomic radii (look at the table here), we can see that they rapidly decrease across the period initially. Looking at the second period, The graph is pretty steep ...
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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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Are there any trends for electrical conductivity?

Which element has the greatest electrical conductivity? (A) $\ce{As}$ (B) $\ce{Ge}$ (C) $\ce{P}$ (D) $\ce{Sn}$ I am unsure of how to approach this problem. Is there some sort of trend for ...
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Ionization energy of neon vs its cationic counterpart

Which requires more ionization energy: $\ce{Ne}$ or $\ce{Ne+}?$ It seems to me like it should be neon because of noble gas configuration, but the answer given is $\ce{Ne+}.$ Does this anything to do ...
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Why is the Ionization Energy of Germanium less than that of Silicon?

I've read that in the 13th period, Ga has higher I.E. than Al because of the filling of the d-orbitals in Ga. The text said they have low penetration,hence they don't shield well and the effective ...
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n+l rule for first member of lanthanide and actinide series

as we all know that if the value of $n+l$ is same then the orbital with lower value of $n$ will get filled first so in case of first member of lanthanide series the configuration is $(\ce{Xe})\mathrm{...
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Predicting atomic weight and density of calcium [closed]

I have a question from school: Assuming that the element Ca had not been discovered, predict using the properties of the known element surrounding Ca its own properties such as its atomic weight ...
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Memorizing the periodic table

Several people have said that the key to understanding chemistry is through memorizing the periodic table. I want to ask if there is a simple technique to learn it, or if I just have to remember ...
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Comparing the EA [duplicate]

What is the electron affinity trend for the oxygen family? I am interested in the question above. I am aware that EA of O $>$ EA of S, but what about the others? Which is having more EA: O or Se? ...
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Why does attractive forces of nucleus increase more than shielding across groups?

When you study the electronegativity of the elements, the general trend is that it rises with increasing group number, and decreasing period. Supposedly this is because the attractive forces of the ...
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Periodic trend in difference of energy between the s and p orbitals

Why does the difference of energy between the 2s and 2p orbitals of the second period elements increase with increasing atomic number? Does this difference increases by moving down a group, e.g. is ...
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Why does basicity of group 15 hydrides decrease down the group?

In my textbook it is written that the order of basic strength of pnictogen hydrides is $$\ce{NH3 > PH3 > AsH3 > SbH3 > BiH3}$$ I tried but could not find any explanation as to why this ...
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why lithium is less reactive than sodium? [duplicate]

Lithium lies above sodium in a group and is also smaller in size. According to periodic trend reactivity decreases from left to right in period and down the group.
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Relationship between electronegativity and atomic radius [closed]

Would someone please explain in detail the relationship between the two? I understand that atomic radius is related to ionisation energy but I can't see how atomic radius may be related to ...
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Why are elements on the right side of the periodic table nonmetallic and gas at room temperature?

Elements on the left side of the periodic table tend to be solid and metallic, elements on the right side of the periodic table are nonmetal and tend to be gases at room temperature, and the semi-...
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Which is more metallic: boron or silicon?

I read somewhere that boron is more metallic. Is it correct? If so, can you please elaborate? The reason why I'm confused is because 2 factors come into play here: When you move towards right, ...
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Why does electronegativity increase across a period?

What explains why electronegativity increases as you move across a period? Does it have something to do with the shielding effect of added electrons?
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Is it possible that atoms with 120 protons are possible, but that atoms with 119 protons aren't possible?

We currently know that there are atoms with atomic number up to 118 are possible. Is it possible that atoms with 120 protons are possible, but that atoms with 119 protons aren't possible? Or are ...
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Memorizing polyatomic ions? Using Periodic Table

In my Chemistry course, we must memorize a list of common polyatomic ions. Is their an easy way of memorizing ions such as Sulfate $\ce{SO4^2-}$ by looking at just the periodic table. I listed the ...
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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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Why don't ionization energies vary linearly going down Group 2?

I understand why the 1st ionization energies (1st IEs) of Group 2 elements decrease down the group. However, why is the difference between 1st IEs of successive elements greater for Be to Ca and ...
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Why is lanthanum a lanthanide and actinium an actinide?

I do know that the lanthanides start with the element lanthanum, but why? Lanthanum doesn't even have an $f$ orbital, so why isn't it considered a transition metal? It's the same way with actinium, ...
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How can an electron shield another electron of the same subshell?

While I was preparing for my upcoming exams, I stumbled upon this sentence which is bothering me quite a bit: The contraction of the lanthanoids is due to the imperfect shielding of one electron by ...
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Change in electronegativity order down a group from groups 13-16 to group 17

In general, going down a group Zeff initially increases but then becomes approximately constant, while electrons are in higher n orbitals, hence valence electrons on average further from nucleus, ...
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Why do the boiling and melting points decrease as you go down group 1 and vice versa for group 7?

I used to think that because an alkali metal needs to lose one electron to complete its outer shell, when the atom increases in size (atomic radius), the electron would be easier to lose as the ...