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 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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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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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 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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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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Exception in trend of increasing ionisation energy across a period

One exception to the trend of increasing ionisation energy across a period in e.g. period 2 is going from N to O. There is no loss of exchange energy in I1 of O, but there is 2K lost in I1 of N, hence ...
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Why do metals form cations?

metals that have a low number of occupied shells such as lithium and potassium should have a stronger electrostatic attraction to their nuclei, so what causes them to always lose their electrons ...
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Thermal stability order of NaF, MgF2 and AlF3

I came up with a question to arrange thermal stability order of $\ce{NaF}$, $\ce{MgF2}$ and $\ce{AlF3}$ and I think the answer is $\ce{NaF>MgF2>AlF3}$ because $\ce{Na+}$ has largest ionic radius ...
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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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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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Lanthanoid Contraction

Why is the radius of Europium so unusually high and out of the general trend ? Moreover, at different sources I am getting different values of radii. In some (e.g., Wikipedia) the radii are following ...
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What's the order of oxidising strength of the oxyacids of Chlorine?

What I have been told is that the acidity of the four oxyacids of Chlorine increase in the order $\ce{HOCl} < \ce{HClO2} < \ce{HClO3} < \ce{HClO4}$. I have also been told that the oxidising ...
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Why is ionization potential considered a periodic property?

Why is ionization potential considered a periodic property??? A periodic property is a one which appears at regular property But we see that every element has some kind of ionization potential
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Relation of Boiling Point and Melting Point with the reactivity of an element

When we look at the trends of periodic table, there is an interesting correlation to be noticed. Along a period, when we look at the trends in reactivity of an element( Both due to electropositivity ...
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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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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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Relationship between effective nuclear load and periodic properties

The effective nuclear charge is defined as the net positive charge experienced by an electron in a polyelectronic atom. It can be calculated using the well-known Stars Rule. Once I have calculated ...
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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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Why does bond angle decrease in the order H2O, H2S, H2Se?

I know that bond angle decreases in the order $\ce{H2O}$, $\ce{H2S}$ and $\ce{H2Se}$. I wish to know the reason for this. I think this is because of the lone pair repulsion but how?
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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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Why is ionisation energy of bismuth lower than lead?

Why is ionisation enthalpy of Bismuth less than that of Lead for it just comes after the latter in periodic table? First ionisation energy of bismuth is 703 kg/mol while that of lead is 715 kg/mol. I ...
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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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Anomalous trends in ionization energy

I want to address two exceptions in the trend of ionization energy across the period, that are causing me problems: Taking the second period as an example : The two exceptions from the general trend ...
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2nd Electron Affinity of halogens

I have seen questions regarding EA but they were all about the 1st EA so this question is not duplicate. I came across a statement which goes like "2nd EA of halogens is almost zero". How is this ...
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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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Solubility of Calcium Fluoride in water

$\ce{CaF2}$ is insoluble in water, but $\ce{CaCl2}$, $\ce{CaBr2}$, $\ce{CaI2}$ are soluble. Why is this so?
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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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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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Trend in the melting point down the group

We know that the atomic radii increases down the group. So, less energy is required to pull out the outermost electron as we go down the group, hence, gradually melting point decreases down the group....
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Atomic radii of Sc, Ti, Fe, and Co

The atomic radius of Sc is $\pu{162pm}$, Ti is $\pu{147pm}$, $\ce{Fe}$ is $\pu{126pm}$, and that of $\ce{Co}$ is $\pu{125pm}$. The electronic configuration of $\ce{Fe}$ is $\ce{[Ar] 3d^6 4s^2}$, and ...
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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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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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Which of the following statements is true about the trend down group 7?

Which of the following statements is true about the trend down group 7 (halogens) with increase in atomic number? The reactivity increases. The atoms get smaller The boiling points ...
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Why is the ionization energy of sulfur anion more than that of oxygen anion?

Which of the following are in the correct order of their ionization energies? (multi-answer question) $\ce{O > S > S- >O-}$ $\ce{F > F- > Cl- > Cl}$ $\ce{O > O- &...
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Why does color of halogen deepens and the boiling point decreases down the group?

Why does the color of the halogens deepens as we go down the group? also why there is a change in physical state of halogens down the group? \begin{array}{c|c} \mathbf{Gas} & \mathbf{Color} \\\...
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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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1answer
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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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