What is the shape of a molecule? - George Zaidan and Charles Morton

Kakšna je oblika molekule? - George Zaidan and Charles Morton

Translator: Nika Kotnik Reviewer: Matej Divjak

What is the shape of a molecule?

Kakšna je oblika molekule?

Well, a molecule is mostly empty space.

Molekula je predvsem prazen prostor.

Almost all of its mass is concentrated

Skoraj vsa njena masa je skoncentrirana v izredno gostem jedru njenih atomov.

in the extremely dense nuclei of its atoms.

And its electrons,

In njeni elektroni, ki odločajo, kako so atomi povezani med seboj,

which determine how the atoms

are bonded to each other,

are more like clouds of negative charge

so bolj oblaki negativnega naboja kot posamezni, določeni delci.

than individual, discrete particles.

So, a molecule doesn't have a shape

Torej, molekula nima oblike na isti način, kot ima obliko naprimer kip.

in the same way that, for example,

a statue has a shape.

But for every molecule,

A za vsako molekulo obstaja vsaj en način ureditve jedra in elektronov,

there's at least one way

to arrange the nuclei and electrons

so as to maximize the attraction

da se poveča privlačnost nasprotnih nabojev

of opposite charges

and minimize the repulsion

in minimalizira odboj enakih nabojev.

of like charges.

Now, let's assume that the only electrons

Predvidevajmo, da so edini elektroni, pomembni za obliko molekule,

that matter to a molecule's shape

are the outermost ones from each participating atom.

tisti najbolj oddaljeni od vsakega atoma.

And let's also assume

In predvidevajmo, da so oblaki elektronov med atomi,

that the electron clouds in between atoms,

in other words, a molecule's bonds,

z drugimi besedami, molekulske vezi, oblikovani kot nekakšne klobase.

are shaped kind of like sausages.

Remember that nuclei are positively charged

Zapomnite si, da je jedro pozitivno nabito

and electrons are negatively charged,

in elektroni so negativno nabiti,

and if all of a molecule's nuclei

in če bi vsa jedra v molekuli združili v en kup

were bunched up together

or all of its electrons were bunched up together,

ali, če bi se vsi elektroni združili v en kup,

they would just repel each other and fly apart,

bi se samo odbijali med seboj in odleteli stran

and that doesn't help anyone.

in to nikomur ne pomaga.

In 1776, Alessandro Volta,

Leta 1776, je Alessandro Volta,

decades before he would eventually invent batteries,

desetletja preden je dejansko iznašel baterijo,

discovered methane.

odkril metan.

Now, the chemical formula of methane is CH4.

Kemična formula metana je CH4.

And this formula tells us

Ta formula nam pove, da je vsaka molekula metana

that every molecule of methane

is made up of one carbon and four hydrogen atoms,

narejena iz enega ogljika in štirih atomov vodika,

but it doesn't tell us what's bonded to what

ampak nam ne pove, kaj povezano s čim,

or how they atoms are arranged in 3D space.

ali kako so atomi urejeni v 3D prostoru.

From their electron configurations,

Iz njihovih elektronskih konfiguracij, vemo, da se ogljik lahko veže

we know that carbon can bond

with up to four other atoms

z do štirimi drugimi atomi

and that each hydrogen can only bond

in da se vsak vodik lahko veže samo z enim atomom.

with one other atom.

So, we can guess

Tako, lahko ugibamo, da je ogljik osrednji atom,

that the carbon should be the central atom

bonded to all the hydrogens.

povezan z vsemi štirimi vodiki.

Now, each bond represents

Vsaka vez predstavlja delitev dveh elektronov

the sharing of two electrons

and we draw each shared pair of electrons as a line.

in vsak par deljenih elektronov narišemo kot črto.

So, now we have a flat representation

Sedaj imamo ploščato predstavitev te molekule,

of this molecule,

but how would it look in three dimensions?

a kako bi izgledala v treh dimenzijah?

We can reasonably say

Lahko rečemo, da ker je vsaka od teh vezi

that because each of these bonds

is a region of negative electric charge

območje negativnega električnega naboja, in enaki naboji se med seboj odbijajo,

and like charges repel each other,

the most favorable configuration of atoms

bi najboljša konfiguracija atomov imela največjo razdaljo med vezmi.

would maximize the distance between bonds.

And to get all the bonds

In da so vse vezi kolikor se da daleč druga od druge,

as far away from each other as possible,

the optimal shape is this.

je najboljša oblika taka.

This is called a tetrahedron.

Imenuje se tetrahedron.

Now, depending on the different atoms involved,

Glede na različne elektrone

you can actually get lots of different shapes.

lahko dobimo veliko različnih oblik.

Ammonia, or NH3, is shaped like a pyramid.

Amonijak, oziroma NH3, ima obliko piramide.

Carbon dioxide, or CO2, is a straight line.

Ogljikov dioksid, ali CO2, je ravna črta.

Water, H2O, is bent like your elbow would be bent.

Voda, H2O, je upognjena, kot je upognjen komolec.

And chlorine trifluoride, or ClF3,

In klorov trifluorid, ali ClF3,

is shaped like the letter T.

ima obliko črke T.

Remember that what we've been doing here

Zapomnite si, da smo tu razširili naš model atomov in elektronov,

is expanding on our model of atoms and electrons

to build up to 3D shapes.

da smo naredili 3D oblike.

We'd have to do experiments

Z eksperimenti bi videli, če so res take oblike, kot smo predvidevali.

to figure out if these molecules

actually do have the shapes we predict.

Spoiler alert:

Kvarnik:

most of the do, but some of them don't.

Večina jih je, ampak nekatere pa ne.

Now, shapes get more complicated

Oblike so bolj zapletene, ko povečamo število atomov.

as you increase the number of atoms.

All the examples we just talked about

Vsi naši primeri so imeli en očiten osrednji elektron,

had one obviously central atom,

but most molecules,

ampak večina molekul od relativno majhnih farmacevtikov

from relatively small pharmaceuticals

all the way up to long polymers

vse do dolgih polimerov, kot je DNA ali proteini, pa ga nima.

like DNA or proteins, don't.

The key thing to remember

Ključna stvar je, da se bodo vezani atomi uredili tako,

is that bonded atoms will arrange themselves

to maximize the attraction between opposite charges

da bo privlačnost med nasprotnimi naboji največja

and minimize the repulsion between like charges.

in odboj med enakimi naboji najmanjši.

Some molecules even have two or more

Nekatere molekule imajo dva ali več stabilnih ureditev atomov,

stable arrangements of atoms,

and we can actually get really cool chemistry

in lahko dobimo res kul kemične reakcije

from the switches between those configurations,

pri preklapljanju med temi konfiguracijami,

even when the composition of that molecule,

celo ko se kompozicija te molekule,

that's to say the number and identity of its atoms,

to je število in vrsta njenih atomov,

has not changed at all.

sploh ne spremeni.