The reaction between sodium and chlorine

De­spite the first part of the ti­tle, our tale will not be about te­dious chem­i­cal sub­stances and their in­ter­ac­tions, our sto­ry is about pas­sion­ate love, and has a hap­py end­ing – the for­ma­tion of a close-knit fam­i­ly.

In our sto­ry, we will at­tend a wed­ding, ob­serve the meet­ing and de­vel­op­ment of re­la­tions be­tween sodi­um and chlo­rine, two lovers with very dif­fi­cult char­ac­ters, watch a fire­works dis­play, vis­it the shore of the Dead Sea, re­veal the se­cret of the so­lu­tion which saves the lives of peo­ple, and much more In chem­istry, ev­ery­thing is like in peo­ple’s lives: meet­ings, re­unions and part­ings.

Imag­ine that we are present at a wed­ding, with mu­sic and flow­ers: sodi­um and chlo­rine have de­cid­ed to live to­geth­er. Or to use the lan­guage of chem­istry, two sub­stances en­ter into a com­bi­na­tion re­ac­tion.

First, let’s get to know the cou­ple bet­ter.

Sodi­um: phys­i­cal and chem­i­cal prop­er­ties

So, let’s meet the groom, “sodi­um”. Usu­al­ly the bride’s par­ents are in­ter­est­ed in where the groom is from. And he has a quite def­i­nite place of res­i­dence in the pe­ri­od­ic ta­ble – 1st group, atom­ic num­ber 11. He is from the group of al­ka­line met­als.

Sodi­um is a sim­ple sub­stance, a sil­very white met­al that is light and soft, ox­i­dizes quick­ly in the air, and re­acts vi­o­lent­ly with wa­ter, with an ex­plo­sion. As we can see, the groom has a dif­fi­cult, ex­plo­sive char­ac­ter.

Ad­di­tion­al­ly, sodi­um in­ter­acts:

• with oxy­gen;
• with many non-met­als (ex­cept ni­tro­gen, io­dine and no­ble gas­es);
• with acids (di­lut­ed and con­cen­trat­ed);
• with liq­uid and gaseous am­mo­ni­um;
• with mer­cury;
• with some or­gan­ic com­pounds.

Chlo­rine: phys­i­cal and chem­i­cal prop­er­ties

Who’s the bride, then?

Chlo­rine is an el­e­ment in the 3rd pe­ri­od of the VII A group, with an atom­ic num­ber of 17.

This is a sim­ple sub­stance, a non-met­al in the group of halo­gens, a yel­low-green poi­sonous gas with a harsh suf­fo­cat­ing smell, it is ther­mal­ly sta­ble, does not burn in air, and when mixed with hy­dro­gen ex­plodes in light.

Be­sides hy­dro­gen, chlo­rine:

• in­ter­acts with non-met­als;
• in­ter­acts with al­most all met­als;
• it forces bromine and io­dine out of their bonds with hy­dro­gen and met­als;
• when dis­solved in wa­ter or al­ka­lis it forms hypochlor­ous, per­chlo­ric or hy­drochlo­ric acid, or their salts;
• with cal­ci­um hy­drox­ide, it forms lime chlo­ride.
• in­ter­acts with or­gan­ic sub­stances.

As we can see, the cou­ple have quite bois­ter­ous na­tures. Both sodi­um and chlo­rine en­ter into re­ac­tions with dif­fer­ent sub­stances and com­pounds.

Al­though sodi­um is a met­al, it is soft and mal­leable: you can cut it with a knife, like but­ter. Chlo­rine is not easy-go­ing, ei­ther – it’s a poi­sonous suf­fo­cat­ing gas, and was the first poi­son to be used in war.

Based on this in­for­ma­tion, you’d think that an al­liance be­tween these two would be sim­ply hor­ren­dous.

But let’s not jump to con­clu­sions. Let’s see what the re­ac­tion of sodi­um and chorine is like, and how they in­ter­act.

2Na + Cl₂ = 2Na­Cl + Q

As we can see, as a re­sult of the re­ac­tion of such seem­ing­ly “rest­less” sub­stances (ex­plo­sive, and chlo­rine is also poi­sonous), a com­pound is cre­at­ed that is quite peace­ful, safe and even ed­i­ble – sodi­um chlo­ride (kitchen salt).

Vis­ual­ly, this re­ac­tion of sodi­um and chlo­rine re­sem­bles a fire­works dis­play. In a flask full of chlo­rine, small pieces of sodi­um are placed – there are flash­es of light, flame, and then thick white smoke! It’s quite spec­tac­u­lar! But this white smoke is in fact tiny crys­tals of kitchen salt. This is how pas­sions flare up be­tween our lovers! It’s more in­tense than a Mex­i­can soap opera!

Now we’ll de­scribe the re­ac­tion of sodi­um and chlo­rine from dif­fer­ent stand­points.

1. On the one hand, this is a com­bi­na­tion re­ac­tion. One sim­ple sub­stance bonds with an­oth­er sim­ple sub­stance, and a com­pound forms.
2. From the en­er­gy stand­point, the re­ac­tion is exother­mic, as it takes place with the re­lease of en­er­gy – light and heat (in the amount of 819 kJ).
3. By its ag­gre­gate state, it is het­ero­genic, i.e. a sol­id sub­stance en­ters into a re­ac­tion with gas, as a re­sult of which a sol­id sub­stance forms.
4. It is an ir­re­versible re­ac­tion, as it pro­ceeds to its com­ple­tion with the for­ma­tion of a sta­ble prod­uct of re­ac­tion.
5. Fur­ther­more, it is an ox­i­da­tion-re­duc­tion re­ac­tion.

Let us look in more de­tail at the last point, as it ex­plains why ex­act­ly sodi­um re­acts with chlo­rine. Let us de­fine what an ox­i­da­tion-re­duc­tion re­ac­tion is. Re­ac­tions ac­com­pa­nied by the trans­fer of elec­trons from one atom to an­oth­er are called ox­i­da­tion-re­duc­tion re­ac­tions.

The ox­i­diz­er is the atom which ac­cepts the elec­trons in the re­ac­tion. The re­duc­er is the one that gives up the elec­trons.

When sodi­um and chlo­rine in­ter­act, the re­ac­tion is ac­com­pa­nied by the trans­fer of elec­trons. Elec­trons in the chem­i­cal world are like mon­ey in peo­ple’s lives. Some have a lot, some have lit­tle, some steal it, some lose it. We’ll see whether it’s the bride or groom do­ing the steal­ing in this case.

The elec­tron­ic struc­ture of sodi­um and chlo­rine atoms

As the atom­ic num­ber of the el­e­ment in the pe­ri­od­ic ta­ble de­ter­mines the charge of its nu­cle­us, and ac­cord­ing­ly its num­ber of elec­trons, let’s ex­am­ine the elec­tron­ic struc­ture of sodi­um and chlo­rine, or fig­u­ra­tive­ly speak­ing, the prop­er­ty of the bride and groom.

Na +11 )1s2 )2s2 2p6 )3s1

CL+17 )1s2)2s22p6)3s23p5

From the elec­tron for­mu­la of sodi­um, we can see that on the out­er elec­tron sub­lev­el it has 1 elec­tron, which it can eas­i­ly give up. For chlo­rine to reach the p-sub­lev­el, it lacks one elec­tron, which it takes from sodi­um.

So to con­tin­ue our sto­ry, the bride takes some of the groom’s prop­er­ty, which he glad­ly shares so they can be to­geth­er.

We should note that chlo­rine is one of the strong­est ox­i­diz­ers. Sodi­um eas­i­ly en­ters into a re­ac­tion with chlo­rine, as one el­e­ment eas­i­ly gives up an elec­tron, and the oth­er eas­i­ly takes it. The fam­i­ly is a close-knit one, in the form of a won­der­ful com­pound, sodi­um chlo­ride. We can hard­ly do with­out kitchen salt, af­ter all – it is in­dis­pens­able in cook­ing; it is used in medicine in so­lu­tions for re­mov­ing swelling; in mu­nic­i­pal ser­vices as an anti-freeze agent; to soft­en wa­ter; and sodi­um chlo­ride is also used in the chem­i­cal in­dus­try.

In­ci­den­tal­ly, the well-known saline so­lu­tion that has saved many peo­ple’s lives is a 0.9% aque­ous so­lu­tion of sodi­um chlo­ride. Click here to see easy ex­per­i­ments with kitchen salt.

Kitchen salt is pro­duced by evap­o­rat­ing saline so­lu­tions. The world lead­er for the pro­duc­tion of kitchen salt is Chi­na. It is found in na­ture in the form of de­posits of halite and sylvi­nite, brines of salt lakes, and min­er­al mix­tures in seas. It usu­al­ly takes the form of white crys­tals, but nat­u­ral salt de­posits can also be blue, yel­low, grey, or even red.

Let’s make a men­tal shift to the Dead Sea.

We don’t drown in it be­cause of the high con­cen­tra­tion of salts dis­solved in it (35 g per 1 liter of wa­ter), in­clud­ing sodi­um chlo­ride.

So, to sum up: the vi­o­lent, un­pre­dictable and some­times poi­sonous sodi­um and chlo­rine have joined to­geth­er; the re­ac­tion has giv­en us the harm­less and even use­ful com­pound of kitchen salt. As we said orig­i­nal­ly, fam­i­ly ties have calmed down two bois­ter­ous na­tures and made them hap­py and harm­less to oth­ers. This is the hap­py end of our sto­ry.