The BE&HM Series ~ Part III: The Main Group Elements, The Octet Rule and Ions

In the previous part of this series, Atoms & The Periodic Table, I went into how the structure of atoms is related to the construction of the Periodic Table of elements.  Some take home points:
  • The mass of an atom is highly concentrated in the central nucleus made up of protons and neutrons
  • The volume of an atom is determined by the space "swept out" by the essentially massless electrons orbiting the nucleus.
  • Electrons travel in ever-widening paths that can be approximated as concentric spheres, and electrons will fill the available paths, aka shells & orbitals, closest to the nucleus before being forced to occupy the next level.  
  • Each shell contains various sub-levels or orbitals.  Depending on the shell these include one s, three p, five d and 7 f orbitals.  Each orbital can contain 2 e's.
  • Interactions between atoms are between the outermost electrons occupying what is called the valence shell.  
  • The chemical behavior of an atom can be predicted based on this valence shell, particularly in the Main Group or Group A elements
  • The horizontal rows of the periodic table correspond to the Principal Quantum Number or outermost occupied shell in the alphabetic designations K, L, M ...
  • The vertical columns of the periodic table include atoms with similar valence shell electron configurations.
With regard to the last three bullet points, it is the Group Number of each column that is most predictive of how atoms will (or won't) interact with each other.  This post will focus on the "A" elements as these are the ones most commonly involved in biochemistry.  

The Octet Rule

direct image link
Most of the Group A elements have a valence shell with an s-orbital and three p-orbitals that can hold a combined 8 electrons.  There are exceptions to this, but the only relevant one we'll discuss is hydrogen, H, with its valence shell of a single s-orbital that can hold 2 e's.  All discussions until further notice, exclude hydrogen as we'll discuss why it is considered a non-metal despite sharing certain characteristics with the rest of the Group IA atoms it is similar to later.  

To understand the Octet Rule, let's consider the sodium atom, Na, depicted at right.  Sodium is atomic number 11 (and has a mass of 23 so its nucleus contains 12 neutrons) so there are 11 electrons orbiting the neutral sodium atom.  I've already discussed how the first shell can hold 2 e's, and the second 8 e's as pictured.  This leaves the 11th electron that must orbit in the next larger M shell, and it is all alone in that space.  Recall, the electrons occupy space by "sweeping it out" rather than filling it.  You have one electron trying to establish this atom's larger volume, trying to do the work of eight!  The 8 electrons in the (middle) L shell are establishing and defending this space against all approaching atoms that might collide with it well, but that single electron is out there on its own.  It is vulnerable to attack.

The valence shells of the Main Group elements have 8 spots to be filled by 8 electrons, and this is the most stable state of the atom, hence, the Octet Rule which merely states that these atoms react and combine to achieve the stable state of a full valence shell with 8 e's.  The remainder of this post will discuss how single atoms go about accomplishing this.

Ions:  Cations and Anions

Let's start with some definitions:
  • Ion:  The charged particle formed when an atom loses or gains electrons so that the number of electrons associated with it differs from its atomic number (e.g. number of protons).  Recall protons and electrons have equal and opposite charges, a neutral atom #e = #P and charge = 0.
  • Cation:  A positively charged ion formed when an atom loses electrons.  When electrons are lost #P > #e, so #(+) > #(-) and the atom has a net positive charge.  
  • Anion:  A negatively charged ion formed when an atom gains electrons.  When electrons are gained #e > #P, so #(-) > #(+) and the atom has a net negative charge.  
  • Which is which?  I remember this by ca+ion and aNion, the t looks like a + and the N is for negative.  
Now let's revisit the sodium, Na, atom with its vulnerable 11th electron.  While the neutral state is desirable, the 8-electron containing valence shell is moreso, and the easiest way for Na to attain that is to cut the 11th electron loose.  This is what happens, although it's probably more correct to say that the electron gets knocked off easily.  And now let's revisit the Periodic Table.

direct image link

The print is small, but looking for #11 in the table, you'll find Na in the third row on the left, and below the Na you'll see 3s1. Scan above and below in that column and notice that the number changes, but the s1 does not. All Group IA atoms share the same valence shell configuration: a single electron in the s-orbital of the outer shell. They all behave like Na, and are more stable losing that "extra" electron. In doing so they become cations with a +1 charge. For "A" groups, Group I = +1 . 

Looking one column to the right, we have the Group IIA elements. That's magnesium, Mg, to the right of Na. I'm betting most can predict what Mg does ... it loses it's 2 e's (still trying to do the work of 8) and becomes a +2 cation. For "A" groups, Group II = +2. Scan up and down that column, and each of these atoms does the same.

Before we jump all the way to the other side of the Periodic Table, let's state this rule:  For the Main (A) Group elements, the number of electrons in the valence shell is equal to the group number.  Quickie Quiz time ...

Q: How many valence electrons in sulfur, S?

A: I find S in the table and see it is a in Group VIA, thus sulfur has 6 electrons in its valence shell. 

Q: Which element is Iodine, I most similar too? F, C or Li? 
A: F, both I and F are Group VIIA elements and have 7 valence electrons.
So now let's skip all the way to the right side of the table, to Group VIIIA.  These atoms have the complete complement of 8 valence electrons.  They are "happy" all the way around -- neutral and with filled valence shells capable of "defending" their space.  These are commonly called the Inert or Noble Gases -- they tend to be gases (as opposed to solids or liquids) at ambient temperatures and they are unreactive.  The octet rule tells us why, because reactions are electron interactions/transactions.  These elements have no need to engage in such to achieve an energetically favorable state.  All matter is lazy -- it seeks out the lowest energy state.  These atoms are already there and don't need to give any other atoms the time of day!!

direct image link
And now we'll go one to the left to Group VIIA.  How many electrons in the valence shells of these atoms?  Seven, and they want eight, so what do you think happens here?  Why they "suck" in an electron and become -1 anions.  Let's use chlorine, Cl, atomic no. 17 depicted at right.  Compared to Na, those 7 e's in the valence shell do a pretty good job of defending the space of the M shell ... but 8 could do better.  When a chlorine atom gains that additional electron it has one more -1 (e) than +1 (P) charge and is thus negatively charged.  

One more column to the left and we have the last cases of Main Group atoms in biological context that form ions.  The group VIA, having 6 valence electrons will gain 2 e's to form -2 anions.  

Not all Atoms form Ions

What of the remaining Groups III, IV and V?  Group IIIA elements do not play a huge role in biochemical compounds so we'll ignore this entirely.  Group IV contains the big guy -- Carbon -- also the only biochemically relevant atom in this group.  Carbon with its four electrons, has a half filled valence shell.  It would have to either lose or gain four electron to become an ion to satisfy the Octet Rule.  This is not energetically favorable, so carbon meets the rule through other means.  So too the biochemically relevant  Group VA elements of nitrogen, N, and phosphorus, P -- they do not form ions to meet the Octet Rule.

Symbols and Terminology

  • Usually referred to as "parent atom ion":  e.g. the sodium ion
  • Superscripts of +n indicate the number of electrons lost, no number indicates +1, sometimes multiple + are used.  Examples:    Na+ , Ca+2 or Ca++

  • Replace the suffix (ygen, ur, ine) with "ide":  e.g. the oxygen atom becomes an oxide ion, a bromine atom becomes a bromide ion.
  • Superscripts of -n indicate the number of electrons gained, no number indicates -1.  Examples:   F- or S-2

Ion Size vs. Atom

I'll mention this here because it may become relevant later.  Atomic size increases more considerably down a column than across a period.  This is because as you go down a column, the atoms have electrons occupying the next larger valence shell whereas across a period you are just adding electrons to an already established volume.  The differences in ion size vs. their parent atom is most pronounced with those cations formed from IA and IIA atoms.  Refer to the picture of the sodium atom, and you can see that losing that one little teeny tiny essentially massless electron makes for a much smaller ion.  The size of ions is often important in transport across biological membranes and such, so I thought this was worthwhile mentioning.  On the other side, however, with the VIIA ions, adding an electron to an almost already filled shell has a negligible effect on the ion size vs. the parent atom.  

Ion Formation, Oxidation and Reduction

The formation of an ion from its parent atom is the most basic process of oxidation or reduction.  Oxidation involves losing electrons, therefore cation formation is oxidation.  Reduction involves gaining electron, therefore anion formation is reduction.

Every atom "comes with" a certain number of electrons in this universe.  All Na atoms come with 11 e's.  When one is knocked off, the remaining 11 protons are only associated with 10 electrons.  We say that Na+ is oxidized.  Conversely when a flourine atom, F, comes with 9 electrons for its 9 protons.  When it takes on an extra electron to become a flouride F- ion, we call the anion a reduced form of flourine. 

Oxidation and reduction to form monatomic ions of  IA, IIA and VIIA elements is generally irreversible in biochemical contexts.  We'll revisit this in coming days why you're in no danger from consuming chlorine atoms as chloride ions from table salt and having them convert to toxic chlorine gas in your body.

Where do the electrons come from?  Where do they go?

This post was getting long, so I decided to end it here with this question.  The electrons are either transferred from one or more atoms to another (or more) atoms in the creation of ions, or they are shared between two or more atoms.  In both cases, substances comprised of two or more different atoms -- called compounds -- are formed.  The means by which these substances are held together is called bonding.  When electrons are transferred, in the formation of a compound the individual atoms become ions that form, you guessed it, ionic bonds and ionic compounds.  When electrons are shared, covalent molecules are formed.   I will devote a separate post to each of these types of bonding and compounds.   I'll leave you with this referring specifically to the endogeneous biological context (dietary sources and supplements can be another matter):
  • Groups IA and IIA elements are always in ionic form
  • Groups IVA, VA and VIA elements do not form monatomic (single atom) ions
  • Group VIIA elements are generally, but not always, in ionic form


Gwen said…
Dear Evelyn,

I'm enjoying this series! I also homeschool my son, and I'm going to hang on to these for assistance.

Thank you!

CarbSane said…
I'm glad, and thank you for the positive feedback!
Unknown said…
Slightly off topic but here is the latest update from our good friend Jimmy Moore

He is now "down" to 274.8 lbs from a high of 306 and is currently eating a diet with an appx 85/12/3 ratio of fat/protein/carbohydrates.

If you assume 2500 calories per day @ his current weight of 274.8 lbs (124.91 kgs) he would be consuming 18.75 grams of carbs (75 calories), 75 grams of protein (300 calories) or .06 grams per kilo of bw and 236.11 grams of fat (2125 calories)

At 2000 calories per day it's 15 grams of carbs (60 calories), 60 grams of protein (240 calories) or .48 grams per kilo of bw and 188.89 grams of fat (1700 calories)

He also says - "Here are a few more examples of the foods I’m consuming on my experiment and the percentage of fat calories:

Coconut oil: 100% of calories from fat
Butter: 99% of calories from fat
Cream cheese: 88% of calories from fat
Sour cream: 87% of calories from fat
Heavy cream: 96% of calories from fat
Cheddar cheese: 75% of calories from fat

Since when is cream cheese, sour cream, heavy cream and cheddar cheese part of a healthy, paleo type diet??
Anonymous said…
I liked:

"I gained nearly four pounds at this Paleo nutritional health conference despite eating pretty darn low-carb. But the difference was I didn’t have access to the extra fat that I need to be successful at nutritional ketosis."

He gained weight from not having access to enough fat....had nothing to do with sitting around and eating at a conference for 4 days. I wasn't there but I've been to plenty of conferences and there's all day grazing and big dinners at night. But it must have been the "low fat" that did it.
Unknown said…
I liked

THANKS Mark! My strength and exercise have not been diminished and I've purposely not increased them (in fact my exercise frequency has gone DOWN by design so as not to confound the results)
CarbSane said…
Ha! Didn't have access to the extra fat. LOL. I hear they were giving out little pots of ghee, and what was stopping him from toting along a jar of coconut oil (or tub of butter) and a spoon?

I dunno about you all, but I'm getting tired of this 40 y.o. man schtick ... almost as much as I'm tired of the 30 y.o. woman bemoaning how old she is. Sheesh. I lost my approx 100 lbs going through menopause in my mid 40's so STFU already! LOL.

OK ... now that I got that off my chest ;) Charles I just had to tweet about this one. He whined about bloggers claiming he was gorging on dairy fat ... then proceeds to list all the dairy fat he ate while focusing on the fat content of his processed sausage.

2-3 oz butter = 1/2 to 3/4 of a stick
but if that's not enough,
3T sour cream
but if that's not enough, let's add (optional)
2oz cheese

All of this added to 4-5 eggs with sausage for one meal. I should HOPE you aren't hungry for a good long time!

Regular readers of Jimmy's menus will recognize what is going on right now and I suspect that behind the rah rah fused with fatalism facade, Jimmy is already worrying. He's lost around 30 lbs in 90 days and his charts show he's plateauing out at around that same 270 mark he oscillated around for 3 years before he lost control of things.

He claims to be taking the Glycosolve he's hawking (along with non-dairy creamer) and yet his blood glucose levels are still bouncing around. Damn that ONE Chinese buffet! ROFLMAOSIP

CarbSane said…
Bwa ha ha! Strength and exercise has not been diminished despite his deliberate "downsizing" of exercise "by design". Ya just can't make this crap up!
Unknown said…
Weight on Day 1 -306.2

Weight on Day 30 - 286.0

Weight on Day 60 - 279.8

Weight on Day 90 - 274.8

Weight loss slowing down dramatically

4-5 pastured eggs (large eggs = 284-355 calories)
2-3 oz grass-fed butter and/or coconut oil (2-3 oz butter = 402-603 calories, 2-3 oz coconut oil = 482-723 calories) )

Sea salt
Parsley (or your favorite spice)
2 oz full-fat cheese (optional) (2-3 oz cheddar cheese = 226-339 calories)
2 Tbs Trinity Hill Farms Sweet Chili Sauce
3 Tbs sour cream (3 tbs sour cream = 69 calories)
1 whole avocado (1 whole avocado = appx 322 calories)

Total = 1785 (using butter+coconut oli) to 2411 - not counting sea salt, parsley and the sweet chili sauce

A great many people don't eat this much in an entire day!!
Unknown said…
exactly what does this mean?? " exercise frequency has gone DOWN by design so as not to confound the results"
Lesley Scott said…
"A great many people don't eat this much in an entire day!!" In the comments section of that post, JM notes: "A meal like that keeps me pretty full most of the day. Sometimes I need two meals to fulfill me. It's a part of that intuitive eating I was talking about."

So that means this meal is repeated twice sometimes. Which would bring that day's total calories to over 5,000 or so. If you're not Michael Phelps, that's a lot of calories.
Unknown said…
Don't forget that he sometimes adds sausage to the meal as well. His weight loss is slowing down - when it stops and he starts gaining again what will his excuse be this time - will it be this " Now that I’m 40 and all the associated metabolic and hormonal changes that come with that"

We await the next 30 day update - my guess is that the weight loss stops or he even regains a pound or two.
LeonRover said…
I can see that we on the verge of a new Eating Paradigm - GKEH -

Go Keto Eat Huge.

Waal, Ah never . . . . . !!!!!

CarbSane said…
I hope the commenter on that thread waiting with bated breath for his menus is pulling his leg! Lawdy that meal doesn't even look appealing.

I note his BG's are all over the map yet he's taking that Glycosolve and eating ketogenic VVVLC, the latter for 3 months now. Must be that one Chinese buffet. Sorry to repeat that but the rationalizing is just too much to bear sometimes :D
markgillespie said…
He obviously wants to be able to attribute all his success to the high-fat diet and not have any nasty ELMMers attribute it to exercise.
CarbSane said…
Readers of his former menus blog might notice this too: He appears to be settling out at around the weight he has oscillated about for the past 2-1/2 years or so when he couldn't seem to shake the weight eating a reported 2000-2500 cal/day (since his portions were always estimated it was likely more as it is very easy to underestimate things like the salad dressing he drowned his fattening side salads with).

No wonder he won't report calories because he's proven time and again that it's not the carbs but the calories that count. He started 2011 more than 15 lbs lighter than he started this experiment yet he lost weight quite a bit faster. It's a mystery why? Naah ... some days he was only eating one meal of around 1500 cal/day. Go figure, eh?
ProudDaddy said…
I'm confused. (What's new?) I thought that his problem was that he wasn't maintaining "nutritional ketosis" due to dietary protein being converted to serum glucose, so he bought a ketone meter to be sure this wouldn't continue to be the case. Now it turns out that he's consuming about the same amount of protein as the average American and perhaps a bit more.

I note that he will not be reporting body composition because his meter is unreliable. You would think that if he can afford the ketone test strips, he could get a DEXA scan pre and post. Or underwater weighing, or even a caliper analysis at his gym!

I was willing to bet that cutting out the protein was going to result in lean body mass loss. Now I find out that protein intake is still normal. So, what is different this time?

I'm confused.
ProudDaddy said…
One thing I'm NOT confused about is that his diet is not paleo by anyone's definition (except perhaps his own). I can't really blame him for trying to latch onto a rising star, but how the paleo camp leaders can stand by and not denounce him, I'll never understand.
Unknown said…
Adam • 12 hours ago
I'm wondering if the sudden change in your weight loss correlated with the introduction of glycosolve. Did the rapid weight loss stop soon after you started taking it?

LLVLCBlog MOD • 12 hours ago • parent −
Nope. Didn't add it until 7-29-12 when I weighed 274.2. On Day 90 of this experiment after taking 2-3 Glycosolve daily for about two weeks as of 8-12-12, my weight was 274.8.

So - from 7/29 until 8/12 he GAINED .4 lbs - Oh well
bob said…
Hi Evelyn,
I am prediabetic and taking glucose readings often. My doc is holding back on any prescription meds for now but said Metformin may be something to consider. I looked at Metformin and also checked JM's Glycosolve. Some studies have shown the primary ingredient in Glyco, Berberine, is as effective or better than Metformin with less adverse side effects. JM has no diabetes indicators so must be taking Glyco for weight reduction. I didn't see much about any benefit on weight loss.

As for his experiment, I see his followers are closely watching and can't wait to implement his new eating plan when published. I'll pass, but may consider taking a jar of coconut oil with me to my next Chinese buffet.
ProudDaddy said…
Bob, since you've already done the legwork, would you list one or two human studies on berberine's effect on serum glucose? Or, would you just tell me the dosage used and average FBG reduction? Thanks.
Unknown said…
Andrew C said…
This comment has been removed by the author.
CarbSane said…
It's called follow the money.

So long as big names go on Jimmy's podcasts, listeners will look the other way at Jimmy himself -- he's doing the lawd's work helping to educate people. So long as his podcasts remain popular, up-and-comers will look to score the exposure. And round and round we go ...

Hopefully he's eating enough protein to prevent lean losses.

Andrew C said…
Jimmy Moore wrote:

> ALTERNATE VARIATION: Cook up 3 slices of bacon or 3 sausage patties first
> and then use the leftover grease from your meat along with some butter
> and/or coconut oil to cook up 3 eggs with it. YUMMY!"

Sausange? Bacon? How can this be? Mr. Moore "CUT RED MEAT". He even gives
blood to lower his iron overload.
Jimmy Moore @livinlowcarbman 12 Aug
> @chriskresser Thank you for looking I to the testosterone cream/iron
> overload issue. I've cut red meat & give blood every 2 months already.
Jimmy Moore @livinlowcarbman 11 Aug
> Next is @ChrisKresser taking on an issue of personal interest regarding
> iron overload. I've been dealing with this in 2012. BRING IT! #AHS12
Tom Pentzer @acrunchyfrog 11 Aug
> @livinlowcarbman testifying about his iron overload. #Ahs12

OOOPS - guess his high meat diet and testosterone cream weren't so healthy
after all?

Solution: BUTTER!
Unknown said…
ALTERNATE VARIATION: Cook up 3 slices of bacon or 3 sausage patties first
and then use the leftover grease from your meat along with some butter
and/or coconut oil to cook up 3 eggs with it. YUMMY!"

Fried eggs in bacon grease, butter AND coconut oil - I'm getting nauseous just reading this.
Unknown said…
If Jimmy wanted to eat a high fat, moderate protein and very low carbohydrate die why not eat like this but cut the portion is half

it would give him appx 2,000-2,250 calories, 60-70 grams of protein and 15-25 grams of carbohydrates per day

you could then adjust the calories down if you weight loss was stalling

why he doesn't follow something like this is confusing to me.
CarbSane said…
I'm curious why he was so proud that he didn't lick his plate?! Pastured butter and CO are not cheap, why would you want to add so much as to leave a slick on the bottom of your plate. Eeeew.

@Andrew, he has cut back on red meat though. 3 slices bacon much less than 1-2 lbs beef/day!
CarbSane said…
< sarcasm >

Reality check P-Daddy! I just heard that the Gedgaudas/Sisson Primal Evolutionary Research Consortium just released evidence of primitive bovines from Cate Shanahan's cave drawings. It appears these ancestral cows lactated straight cream and butter with none of that pesky protein and carb. Of course it evolved to add those things into its infant food, but this shows for the first time that dairy fat is the preferred fuel of primal humans!

< /sarcasm >
Unknown said…
LLVLCBlog MOD • 5 hours ago • parent −
Pretty much it's the same putting the emphasis n fat while titrating carbs and protein. I'm not counting calories but my satiety doing this doesn't require a lot of food.

Is he freaking kidding - not a lot of food - with that breakfast egg melange of around 2000 calories!!!!