In this video excerpt from NOVA"s "Hunting the Elements," New York Times technology columnist David Pogue examines just how atomic framework determines reactivity. Accomplish Theo Gray, chemist and author, that helps David check out how the electron construction of an atom affects its capacity to integrate with various other atoms. Discover why noble gases space not reactive and also why halogens and also alkali metals are highly reactive.

You are watching: Why are alkali metals and halogens so reactive

Permitted use:



Source: NOVA: "Hunting the Elements"

This media asset to be excerpted native NOVA: "Hunting the Elements."

Here are few of the main principles students need to take far from this video:

The place of electron in one atom deserve to be defined as concentric shells around the nucleus of the atom.The number of electrons in the outermost covering of an atom determines its reactivity. Noble gases have low reactivity since they have full electron shells.Halogens are highly reactive due to the fact that they readily get an electron to fill their outermost shell.Alkali metals are extremely reactive since they readily lose the solitary electron in your outermost shell.

Questions because that Discussion

Why room noble gases sometimes dubbed inert gases?Think of and also describe one analogy to help you remember even if it is noble gases space reactive.What walk the host mean when he states “reactivity is a shell game”?In regards to electrons, what do elements located in the same column of the regular table have actually in common?


DAVID POGUE (Technology Guru): The noble gases.

See more: A Who Wrote The Theme Song For &Quot;The Beverly Hillbillies&Quot;?

Where does the term "noble gases" come from? are they nobility? perform they sirloin to rescue maidens?

THEO GRAY (Chemist and also Author): No, you"re reasoning of heroes. They room like nobility in the feeling that castle don"t mix with the riffraff. Lock don"t like to reaction with any kind of other elements.

By and also large, it"s not possible to form compounds v them.

DAVID POGUE: Well, it"s a shame because that your arsenal that they are gases, because you"ve got large blanks here. Oh, ho, ho, ho! The noble gases, choose neon and also argon, posture a problem for chemistry who favor their facets to join forces and react through each other. You deserve to run one electric existing through them, excite their electrons and also get pretty colors—which is how neon lights work—but the noble gases don"t react.

They pretty much refuse to integrate with various other elements.

THEO GRAY: gift an inert gas, gift unwilling to mix v the various other elements, react with them, this is a really clear-cut distinction that set apart this specific column from every the rather in the routine table.

DAVID POGUE: so why are these males so aloof? together it turns out, proton may determine the identification of an element, however electrons ascendancy its reactivity. And also reactivity is a covering game.

Here"s exactly how the video game is played.

Imagine that these balls are electrons, and also the target is one atom. Electron don"t just pile on around the nucleus. Similar to skee-ball, wherein you land, loved one to the center counts.

Oh come on!

The electrons take up location in what deserve to be assumed of together concentric shells. The first shell maxes the end at just two electrons, the following holds eight, climate it goes up to eighteen. One atom with eight electron in its outer shell makes one happy, solve atom.

And noble gases come pre-equipped with fully satisfied shells.

And is this the only shaft like that?

THEO GRAY: It"s the only column where all the shells are fully filled.

DAVID POGUE: but what around the column just prior to those stable noble gases? they are referred to as the halogens. They have actually an external shell that needs simply one much more electron to it is in full. And also they"ll grab the any way they can. The group contains fluorine and bromine, yet the most infamous is chlorine: 17 protons surrounding by 17 electrons, arranged in 3 shells that two, eight and seven, one short of being full.

It"s that extra electron chlorine will acquire any method it can, occasionally with violent results. That"s why chlorine gas was offered as a deadly poison in people War One.

THEO GRAY: Chlorine, ns mean, this is nasty stuff. This will take electron from kittens. It"ll go and steal an electron from off the water in your lungs and turn it come hydrochloric acid, because it really desires an electron.

DAVID POGUE: Yeah, maybe I"ll leave that whereby it was.

THEO GRAY: Now, if you walk the other direction, you finish up v the alkali metals.

DAVID POGUE: The alkali steels are the very first column. Each of lock has complete shells, plus one extra electron sit in a new, outer shell.

They have familiar names favor lithium, sodium and potassium. And also they all want to eliminate that single, lonely electron, any means they can.