The Periodic Table

7:59 AM

heyy

i am a little confused about the concept of valency

so all the group 1 elements have a valency of +1

because they make ionic bonds

well then what is the valency of carbone?

it makes covalent bonds right?

then it cant be +4 or -4

as it doesnt donate any electrons

@MartianCactus what does +4 have to do with covalence?

covalence?

covalent bonds

i dont rly get the concept tho

what is the valency of group 1 elements?

1

8:12 AM

my teacher said it is +1

how can you say it is 1?

ok +1

i mean what is the reason behind it

why +1 even?

because it has one electron in its outermost shell

why do we say that their valency is +1?

e.g. sodium is 2,8,1

8:13 AM

so carbon has 4 electrons

so its valency is 4?

yes

and what about oxygen

is its valency 6?

yes

wait what?

i thought it was 2

like -2

what is the definition of valency?

8:15 AM

i think its the amount of hydrongen atoms something can combine with

tho im not sure

thats why i am asking

i thing oxygen has 6 valence electrons

but its valency is -2

then what about carbon?

are you learning from a textbook?

yes

10th grade

then open that textbook and find its definition

it says the "combining power of the element"

but then it says that valency can be either 1, 2, 3 or 4

hmm...

is there any examples of valency in your textbook?

8:17 AM

but when my teacher is teaching she adds + and - signs for some reason

and i think thats related to oxidation states

wait

lemme check

Quantum AMERICCINO

Hello everyone. Does anyone have experience with the parallel factor analysis method used in analytical chemistry?

@DHMO yes i found it!

now i am a little bit more confident about the concept

i had to skim thorugh my previous grade books

they say that the valency of carbon is 4

and oxygen?

and oxidation state is just another thing which i was confusing with valency

oxygen's is 2

ok

8:27 AM

they say that the valency is the combining capacity of an element

which is equal to the number of electrons which it can lose, gain or share to reach an octet

so oxygen has 6 electrons

it doesnt give all of them away as it will take more energy

so it can either share 2 of them to make a covalent bond

or gain 2 of them through ionic bond

in either case, the number of electrons is 2

so valency is 2

alright

and does that contradict with your teacher?

''valency'' is in the list of my most hated words

yes it does contradict

she is adding + and - values to valency

which i think is wrong

i think she might be talking about charge

but she wrote valency in notes

8:54 AM

@MartianCactus do take note of the comment above you

"valency" is really a bad concept

why?

it is used everywhere

Because it's a bad concept

i thought it was like a very important thing

just as imp as the periodic table

Only to high schoolers

without which chem wont exist

8:55 AM

@M.A.R. but you can determine structure from valency?

formal charges also depend on valency?

so u guys dont use valency?

@MartianCactus Well, it's never too late to change your mind

yeah

@DHMO I dunno, if we're talking about methane probably

but the pros dont use valency?

8:56 AM

Never.

NEVER EVER.

And it's not called pros. It's called chemists

@MartianCactus google "hypervalency" to destroy the concept

OK, gotta do some studying. AFK

but i kinda like valency :(

why IS it a bad concept tho?

what is the valency of S?

2

8:59 AM

then what is SF6?

oh yeah

it goes the other way binding with the 6 Fluorines

yeah but that kinda destroys the purpose of valency

maybe it really is a bad concept

or maybe its just saying that "most of the time it will do this but you can never be too sure"

i think you can use it in only C H O N F so that it is consistent

although it still kind of fails

because H3+...

ozone (O3)...

nitric acid (HNO3)?

i dont know what you are talking about now :/

DHMO werent u in the math chat too the other week?

yes

does the theory of valency account for the seemingly 5 bonds formed in HNO3 by N?

5 bonds?

9:04 AM

find its structure online

oh

;;structure HNO3

whats the command tho?

ah nvm

!!img/HNO3

yeah it does account for it

N donated an electron to O

now it needs 4 electrons

so it makes 4 bonds

dont ya thing?

9:08 AM

alright

hmm...

but WHY it donated 1 electron

thats something that valency cant explain

i think not

en.m.wikipedia.org/wiki/Trihydrogen_cation

what about this

!!img/H3

Chemobot

well thats odd...

so the hydrogen

wait

9:12 AM

it is supposed to be a triangle

how can it even make 2 bonds when it has only 1 electron?!!?!?!?!

how can it make 2 electrons

well that's the point

i dont know how this is happening

Also diborane

!!img/B2H6

Chemobot

9:18 AM

Brain explosion in 5, 4, 3, 2, 1 . . .

@Chemobot I feel like kicking you right now

!!img/B2H6

Chemobot

so boron needs 5 electrons

but its only taking 4

and hydrogen magically flicks out an extra electron somehow

idk thats some hardcore chem

maybe if someone else can explain

these examples only serve to show tha valency is a bad concept

yeah i guess

12:56 PM

@DHMO @MartianCactus @M.A.R. Situations like nitrate when valency appears to fail due to too many electrons around an atom (hypervalency) can usually be explained by charge-shift bonding:

Charge-shift bond

The charge-shift bond has been proposed as a new class of chemical bond that sits alongside the two familiar families of covalent and ionic bonds where electrons are shared or transferred respectively. The charge shift bond derives its stability from the resonance of ionic forms rather than the covalent sharing of electrons which are often depicted as having electron density between the bonded atoms. A feature of the charge shift bond is that the predicted electron density between the bonded atoms is low. It has long been known from experiment that the accumulation of electronic charge between...

It's a resonance between the covalent $\ce{A-B}$ and one or both ionic forms $\ce{A^+ B^-}$ and $\ce{A^- B^+}$.

In more or less the same way that benzene has a resonance between the two three-double-bond configurations.

1:28 PM

@hBy2Py is this anything new?

2:14 PM

@DHMO Sason Shaik et al. have been developing the theory for at least 25 years.

Is this any different from resonance?

Dative bonds?

It's a form of resonance.

It's not the same thing as a dative bond.

$\ce{F2}$ has very large charge-shift character

And I don't think anyone would call it datively bonded. :-)

what is it really

it isn't defined in your link

@hBy2Py It's essentially this.

ok

2:18 PM

Basically, when a system tries to cram too many electrons in an interatomic space, Pauli repulsion "squeezes" electrons around/out to the "external" regions of the system/bonding region.

2:46 PM

2

Google search for "Borate"

@CowperKettle hi

Evening!

Jan

@hBy2Py I thought, resonance effect was a different name for mesomeric effect? Hence this questino makes no sense to me …

I need to translate one term. A kind of method used to determine a protein's glycation profile.

It's boron affinity HPLC in Russian

But possibly it's boronate affinity HPLC in English

I'm not sure (0:

Is it always "boronate" in this kind of HPLC, I wonder.

@CowperKettle google confirms

2:58 PM

@DHMO Yes, it confirms. It's that I'm not at all knowledgeable in this, and decided to double-check (0:

3:37 PM

@Jan I have no idea, I don't really know either the inductive or the mesomeric effect.

5:19 PM

so

i have a furiously overwhelming question

why is the atomic size of noble gases larger than the atomic size of halogens when atomic sizes decrease across a group?

i did search it up on the net

and asked my teacher

but everyone says that because noble gases are usually not bonded

but

why does being "not bonded" increase atomic size?

or rather

why does being "bonded" decrease atomic size?

6:36 PM

> pH meter tank 063-PHL

Can this mean "tank-mounted pH meter"?

this word "tank" is mysterious; from a list of equipment

dunno how to translate

7:02 PM

Type 63 (tank)

The Norinco Type 63 (Chinese: 63式; pinyin: Liùsān shì) is a Chinese amphibious light tank. First fielded in 1963, it is in many ways similar to the earlier Soviet PT-76. However, contrary to the popular belief, it does have some essential differences from the PT-76 in the vehicle's waterjet propulsion system, etc. It is also known under its industrial designation, the WZ-211. == Development history == The Chinese obtained a few PT-76 amphibious light tanks from the Soviet Union in the mid-1950s. In October 1958, the PLA decided to develop an indigenous amphibious tank based on the PT-76 design...

@CowperKettle Maybe something like this?

Hard to say without more context

@hBy2Py yes, it's tank-mounted

case solved (0:

@MartianCactus Because the values for all other atoms are usually covalent radius being reported, but in the case of noble gases with normally no bonds to other elements, it's van der waals radius

@CowperKettle In the army, we had a tank-mounted mass spectrometer.

2

7:19 PM

LOL

a Bruker MM1 mobile GC/MS