First post, hello, I have a lot of questions.

[exchemist]

19 minutes ago, Jack777 said:

Sorry. I meant the people back back then who used the terms hooks.

How did they determine if something was bonded?

This set of formulas above is quite complicated to me. It's difficult to visualize. I'm sure in time I'll get there.

Thanks again.

By observing the proportions in which substances reacted. Once you have the atomic weights, if you carefully weigh the reactants and the products, you can deduce that one carbon atom reacts with 4 hydrogen atoms, or else to produce substances with the ratio nC atoms: 2n+2 H atoms. In other words, CH4, C2H6, C3H8………..etc. These are all hydrocarbons. Probably easiest to do it by burning some of a hydrocarbon and measuring the amount of water and carbon dioxide produced and looking at their ratios.

And then it dawns on you that C is joining to 4 other atoms, either 4 Hydrogen or else to one or more C atoms and H for the remainder, but H is only joining to one other atom. The lines between that atoms signify that C can join to 4 atoms but H can only join to 1 . This led to the idea that the number of “bonds” an atom can form is characteristic of the element.
 

And that is a very powerful principle in chemistry.

Edited Thursday at 02:25 PM by exchemist

[Jack777]

2 minutes ago, exchemist said:

By observing the proportions in which substances reacted. Once you have the atomic weights, if you carefully weigh the reactants and the products, you can deduce that one carbon atom reacts with 4 hydrogen atoms, or else to produce substances with the ratio nC atoms: 2n+2 H atoms. In other words, CH4, C2H6, C3H8………..etc. These are all hydrocarbons. Probably easiest to do it by burning some of a hydrocarbon and measuring the amount of water and carbon dioxide produced and looking at their ratios.

And then it dawns on you that C is joining to 4 other atoms, either 4 Hydrogen or else to one or more C atoms and H for the remainder, but H is only joining to one other atom. The lines between that atoms signify that C can join to 4 atoms but H can only join to 1 . This led to the idea that the number of “bonds” an atom can form is characteristic of the element.
 

And that is a very powerful principle in chemistry.

A principle I don't yet grasp because how do they measure atoms? I guess I have to learn about atomic weights.

[exchemist]

32 minutes ago, Jack777 said:

A principle I don't yet grasp because how do they measure atoms? I guess I have to learn about atomic weights.

I made a post about, that a while back on this thread. 
 

But the idea of bonds, and thus the meaning of the diagrams @studiot showed you, should not be too hard for you to understand, I hope.

Water is H-O-H. Carbon dioxide is O=C=O (double lines in the latter case denoting what are called “double” bonds. Note that in this case carbon still forms 4 bonds, even though here it is joined to only 2 other atoms.) So you can see O, oxygen, forms 2 bonds, C, carbon 4 and H, hydrogen 1. 

Edited Thursday at 03:01 PM by exchemist

[Jack777]

2 minutes ago, exchemist said:

But the idea of bonds, and thus the meaning of the diagrams @studiot showed you, should not be too hard for you to understand, I hope.

Sorry, it is hard for me to understand. I'm going to read the books I bought and hopefully I will be able to grasp it. 

[studiot]

2 hours ago, Jack777 said:

Sorry, it is hard for me to understand. I'm going to read the books I bought and hopefully I will be able to grasp it. 

This table might help and it will be useful in time period 4 the last in our history.

I am showing what happens with one gas that doe not combine with itself (helium) and three gases where two atoms of each of the gases combine with each other to form one molecule conprising two atoms. That is a diatomic molecule.
Helium is a monatomic molecule.

The valencies are 0, 1, 2 3   - I don't know of any diatomic gas molecules formed from atoms with higher valencies than 3.

So the pattern is that you require two atoms , alike or different to form one bond.  - my examples are both alike for ease.

It is also possible to more than two atoms to combine to form molecule but that will always involve additional bonds.

Note the number of hooks is the same as the valency.

If you hook two hooks together you get one bond.

If you have zero valency there are no hooks which is why two helium atoms will not join together so a helium molecule has only one atom in it and is called monatomic.

side note

Careful here, you may come across the terms monovalent, divalent and trivalent.

There is no term for nil valent.

end side note

 

Molecules occur mostly in gases. Solids can be quite different.

Do you understand anything about solids, liquids and gases. Have you heard of the kinetic theory ?

 

[Jack777]

1 hour ago, studiot said:

This table

I apologize in advance, this too is still over my head. Honestly, way over my head. I'm still trying to grasp how they knew something was a molecule.

I just started listening to a podcast today called The History of Chemistry by Steve Cohen. So far this is easy for me to follow and understand. I like what he said how it was described, "A chemical process is invisible with no obvious explanation." 

If you need to quit I'll understand as this is a slow process for me but I will eventually get it.

Thanks.

[studiot]

5 hours ago, Jack777 said:

If you need to quit I'll understand as this is a slow process for me but I will eventually get it.

Don't worry, no need to quit.

 

Sir Isaac Newton did not know why things stuck together he just had to accept it because he could see that it happened.

Here are his words from a very long article in the link at the top of the quote.

Quote

https://pmc.ncbi.nlm.nih.gov/articles/PMC7321411/

 

Sir Isaac Newton addressed the question of attraction between atoms in Query 31 of his work Opticks [74], and gives a good contemporary view of the ideas concerning the forces between atoms. After writing “The Parts of all homogeneal hard Bodies which fully touch one another, stick together very strongly. And for explaining how this may be, some have invented hooked Atoms, which is begging the Question; and others tell us that Bodies are glued together by rest, that is, by an occult Quality, or rather by nothing; and others, that they stick together by conspiring Motions, that is, by relative rest amongst themselves”, he continues with his own ideas, “I had rather infer from their Cohesion, that their Particles attract one another by some Force, which in immediate Contact is exceeding strong, at small distances performs the chymical Operations above-mention’d, and reaches not far from the Particles with any sensible Effect”. In the text, Newton shows a broad knowledge of chemistry but, like most of his contemporaries, does not always make a clear distinction between physical change and chemical reaction. In many respects the ideas of Newton are closely related to the ideas of chemical affinity and he gives examples of chemical reactions arranged in a similar manner to Geoffroy

 

He was right, there is a force, he knew nothing of,  which we will discover is the electric force between positive and negative when we move on to the last  1900 to present day period.

 

I offer the philosophy that you can learn enough of the maths, physics and chemistry to be able to recognise things when you see them (not only here but in books or elsewhere) and accept that ther are people who can work out the detail.
Remember that no one person knows enough to work out the detail of everything.
So we must cooperate like atoms in a molecule.

 

That is the principle I am trying to build up to.

Molecules can only works as the cooperative effort of several (perhaps many) atoms acting as one single unit or entity.

So if my detail was too much, just accept you can recognise the sticks as bonds in the stick diagrams.

 

[Jack777]

On 2/28/2025 at 7:50 AM, studiot said:

Molecules can only works as the cooperative effort of several (perhaps many) atoms acting as one single unit or entity.

Thanks. I've been listening to podcasts and reading so I'm slowly learning some stuff.

Here's my notes I've made so far while listening:

ractical chemistry.

Fire

Fermenting.

Learning how the ancients created copper from ore. Natron.

Bronze.

Gold.

Mercury might have been discovered with silver mining.

Cinnabar.

1st century CE, indicator paper.

Thales.

Khemeia

Ascetic acid from vinegar

Lemon juice

Mineral acid. How is this made?

Used for assaying metals.

Distillation & filters.

Alcohol is a good solvent.

Nitric and hydrochloric acid can dissolve gold?

Ammonia from distilled urine.

Metallurgy

When lead was melted its weight increased.

Double displacement

Torricelli & Boyle

Brandt phosphorus

Phlogiston and calx

Conservation of mass

Specific heat. Electrons?

 

1800’s, organic chemistry

Avogadro’s constant. How in the world did he come up that?

[KJW]

On 2/24/2025 at 11:25 AM, KJW said:

For example, if we simply wish to check that the substance is what it is claimed to be...
...
By contrast, if the substance is truly unknown...
...

Another example is a chemical synthesis, the product of a particular chemical reaction on a starting material whose structure is known by whatever means. It may be that the substance produced has never been produced before. In this case, there is no known sample with which to compare our substance produced. But the substance produced is not entirely unknown, either. It is likely to be the substance that was intended to be produced on the basis of what is known about the chemical reaction. And if it is not the substance that was intended to be produced, then it is likely to be in some way related to the starting material or the substance that was intended to be produced. In either case, it becomes much easier to analyse the spectra of the substance than if the substance is truly unknown. Proton nuclear magnetic resonance spectroscopy is especially useful in this regard.
 

[studiot]

4 hours ago, Jack777 said:

Avogadro’s constant. How in the world did he come up that?

The short answer is :  He didn't.

Avogadro was a lawyer turned Physicist. He was not a chemist.
Although in his day there was not real distinction between Physics and Chemistry.

I see you have some other names in your list.

4 hours ago, Jack777 said:

Torricelli & Boyle

During the end of the 17hundreds and into the early 18hundreds what are known as 'the gas laws' were discovered and some of the these were associated with Torricelli and Boyle.

There was a problem however in that careful weight measurements could not be reconciled with the idea that each element had a smallest particle called an atom.

In 1811 Avogadro published a paper in French (although he was Italian) which now appears in every school textbook as

At the same temperature and pressure equal volumes of gas contain the same number of molecules.

Avogadro did not use the word molecule in our modern sense he meant particle. But he did include the words "if you assume that the smallest particles of an element may be made up of more than one atom. "

This and our modern version make up Avogadro's Hypothesis.

An Austrian named Loschmidt was the first to calculate the number of these particles, but he worked on a cubic centimetre.

The modern version we call Avogadro's number in his honour is arrived at on the basis of molecular weight.

The molecular weight of a substance is the sum of the atomic weights of all the atoms making up the molecule.

The atomic weight of Hydrogen is 1 and the atomic weight of Carbon is 12

So looking back at our ethane molecule. This has 2 carbon atoms and 6 hydrogen atoms

So the molecular weight of ethane is (2 x 12) + (6 x 1)  = 30

 

I did ask last time if you have heard of the kinetic theory of gases.

To understand more detail this is needed so an answer would be appreciated.

 

[Jack777]

44 minutes ago, studiot said:

The molecular weight of a substance is the sum of the atomic weights of all the atoms making up the molecule.

The atomic weight of Hydrogen is 1 and the atomic weight of Carbon is 12

This is good. But I still have to somehow wrap my head around how they knew there atoms.

44 minutes ago, studiot said:

To understand more detail this is needed so an answer would be appreciated.

Sorry, I've never heard of this but to be honest this is too much too soon. 

I actually bought a cartoon book for children but even here they assume a body of knowledge about atoms. 

I'm going to have to take a break as I just can't seem to grasp this.

[KJW]

2 hours ago, Jack777 said:

I still have to somehow wrap my head around how they knew there atoms.

Perhaps it would help if you read the Wikipedia article on the history of atomic theory:

https://en.wikipedia.org/wiki/History_of_atomic_theory

Knowing the history of atomic theory provides an understanding of how the knowledge of atoms developed over time.

 

[studiot]

6 hours ago, Jack777 said:

This is good. But I still have to somehow wrap my head around how they knew there atoms.

That is why I have been holding back about the last stage and how we got to our present view of atoms and molecules.

If you look at pages 38 and 39 of the World Treasury book I recommended and I believe you bought you will find the first two pages of an article about electrons by early 20th century physicist George Gamow.
Never mind the electrons we will come to them eventually so don't bother to read the whole article for now.

I have mentioned divisibility and indivisibility a couple of times in this thread. The ancient Greeks spent a lot of time arguing about this subject. The arguments were not just to do with substances and matter but space and time as well. The famous paradoxes of Zeno are some examples. The Aristotle camp believed that you could go on cutting matter into smaller and smaller pieces for ever. That is an infinite count of cuts.

As George describes the alternate camp led by Democritus believed that you would reach a stage where you could cut or divide no more. This he believed that there waas a smallest particle he called atomos.

We do not now how a clear reason why he thought this.
But we do know that the Greeks never resoved their argument.

 

Roll on just over two thousand years and Dalton and other scientists discovered evidence to support this contention.

They found that regardless of how many experiments they did the proportions in either their analysis or their synthesis of substances was always the same regardless also of the total quantities employed.

It was clled The Law of Constant Proportions.

This law has remarkable implications because it means that if you try to synthesise a substance from its elements in any old proportions there will always be and amount of substance and an amount of one element or another left over unused.

Think very hard about this because it can only be true if Democritus was right and there is a smallest piece of any substance or element.

For example you cannot tack on an extra third or one sixteenth of a piece of oxygen to water.

 

Come back and talk about this idea until you are happy with it and then we can  move on again.