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

Prevoditelj: Marijana Žgela Recezent: Ivan Stamenković

What is the shape of a molecule?

Kojeg su oblika molekule?

Well, a molecule is mostly empty space.

Najvećim dijelom molekula je prazan prostor.

Almost all of its mass is concentrated

Gotovo sva masa koncentrirana je

in the extremely dense nuclei of its atoms.

u jezgrama atoma ogromne gustoće.

And its electrons,

A njeni elektroni,

which determine how the atoms

koji određuju kako se atomi

are bonded to each other,

međusobno povezuju,

are more like clouds of negative charge

više su poput oblaka negativnog naboja,

than individual, discrete particles.

nego pojedinačne, određene čestice.

So, a molecule doesn't have a shape

Molekula nema oblik

in the same way that, for example,

kakav na primjer

a statue has a shape.

može ima statua.

But for every molecule,

No, za svaku molekulu

there's at least one way

postoji barem jedan način

to arrange the nuclei and electrons

da se rasporede jezgre i elektroni

so as to maximize the attraction

u kojem će se povećati privlačenje

of opposite charges

suprotnih naboja

and minimize the repulsion

i smanjiti odbijanje

of like charges.

istoimenih naboja.

Now, let's assume that the only electrons

Pretpostavimo da su jedini elektroni

that matter to a molecule's shape

koji su bitni za oblik molekule

are the outermost ones from each participating atom.

oni koji se nalaze najdalje od svakog atoma

And let's also assume

Također, pretpostavimo

that the electron clouds in between atoms,

da elektronski oblaci između atoma,

in other words, a molecule's bonds,

tj. molekulske veze,

are shaped kind of like sausages.

imaju pomalo oblik kobasica.

Remember that nuclei are positively charged

Jezgra je pozitivno nabijena,

and electrons are negatively charged,

a elektroni su negativno nabijeni

and if all of a molecule's nuclei

i kada bi se sve jezgre

were bunched up together

skupile na gomilu

or all of its electrons were bunched up together,

ili svi elektroni skupili na gomilu

they would just repel each other and fly apart,

oni bi se samo odbili i razletjeli,

and that doesn't help anyone.

a to nikome ne pomaže.

In 1776, Alessandro Volta,

1776 godine, Alessandro Volta,

decades before he would eventually invent batteries,

svogdesetljećima prije svog otkrića baterije,

discovered methane.

otkrio je metan.

Now, the chemical formula of methane is CH4.

Formula metana je CH4.

And this formula tells us

Ona nam govori

that every molecule of methane

da se svaka molekula metana

is made up of one carbon and four hydrogen atoms,

sastoji od jednog atoma ugljika i četiri atoma vodika,

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

ali nam ne govori što je s čime povezano

or how they atoms are arranged in 3D space.

ili kako su njeni atomi raspoređeni u 3D prostoru.

From their electron configurations,

Iz elektronskih konfiguracija C i H

we know that carbon can bond

znamo da se C atom može vezati

with up to four other atoms

za četiri druga atoma

and that each hydrogen can only bond

a da se svaki H atom može vezati

with one other atom.

samo s jednim atomom.

So, we can guess

Možemo pretpostaviti

that the carbon should be the central atom

da je ugljik centralni atom

bonded to all the hydrogens.

povezan na sve atome vodika.

Now, each bond represents

Svaka veza predstavlja

the sharing of two electrons

dijeljenje dva elektrona

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

i mi crtamo svaki podijeljeni par elektrona kao crticu

So, now we have a flat representation

Sad imamo plošni model

of this molecule,

ove molekule

but how would it look in three dimensions?

ali kako bi ona izgledala u tri dimenzije?

We can reasonably say

Možemo reći da se

that because each of these bonds

zbog toga što je svaka veza

is a region of negative electric charge

područje negativnog naboja,

and like charges repel each other,

a istoimeni naboji se odbijaju,

the most favorable configuration of atoms

najpovoljnija konfiguracija

would maximize the distance between bonds.

ona u kojoj će veze biti najudaljenije.

And to get all the bonds

A da bi se sve veze

as far away from each other as possible,

udaljile što je više moguće,

the optimal shape is this.

ovo je optimalni oblik.

This is called a tetrahedron.

To se zove tetraedar.

Now, depending on the different atoms involved,

Ovisno o tome koji se atomi povezuju

you can actually get lots of different shapes.

možete dobiti puno različitih oblika.

Ammonia, or NH3, is shaped like a pyramid.

Amonijak, ili NH3, ima oblik piramide.

Carbon dioxide, or CO2, is a straight line.

Ugljikov dioksid, ili CO2, je ravna linija.

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

Voda, H2O je savijena, kao što se savija lakat.

And chlorine trifluoride, or ClF3,

a klorov trifluorid, ili ClF3

is shaped like the letter T.

ima oblik slova T.

Remember that what we've been doing here

Ono što smo radili ovdje

is expanding on our model of atoms and electrons

je širenje modela atoma i elektrona

to build up to 3D shapes.

kako bismo dobili 3D oblik.

We'd have to do experiments

Trebali bismo ispitati

to figure out if these molecules

imaju li molekule zaista

actually do have the shapes we predict.

oblik koji smo predvidjeli.

Spoiler alert:

Pozor!

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

Većina ih ima, ali neke nemaju.

Now, shapes get more complicated

Dakle, oblik se komplicira

as you increase the number of atoms.

kada se poveća broj atoma.

All the examples we just talked about

Svi primjeri koje smo spomenuli

had one obviously central atom,

imali su jednan očiti centralni atom

but most molecules,

ali većina molekula

from relatively small pharmaceuticals

od relativno malih lijekova

all the way up to long polymers

do velikih polimera

like DNA or proteins, don't.

kao što su DNK ili proteini nema

The key thing to remember

Treba zapamtiti

is that bonded atoms will arrange themselves

povezani atomi će se rasporediti tako

to maximize the attraction between opposite charges

da se maksimalno poveća privlačenje, među suprotnim nabojima

and minimize the repulsion between like charges.

i najviše smanji odbijanje među istoimenim nabojima.

Some molecules even have two or more

Neke molekule imaju čak dva ili više

stable arrangements of atoms,

stabilnih rasporeda atoma,

and we can actually get really cool chemistry

i zbog mijenjanja konfiguracija

from the switches between those configurations,

kemija može biti prilično zanimljiva,

even when the composition of that molecule,

čak i kada se struktura te molekule

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

tj. broj i vrsta atoma

has not changed at all.

nije uopće mijenjao.