[mxplxxx (OP)]

An atom consists of protons and a proton is a hydrogen atom. This doesn't make sense. It is like saying a car consists of parts and a part is a car. Why is this so?

[Colin2B]

A proton on its own is not a hydrogen atom, you need to add an electron.

[mxplxxx (OP)]

A proton on its own is not a hydrogen atom, you need to add an electron.

Thx, but your answer is not to the point. Instead of atom use ion.

[Colin2B]

In that case you are hitting a problem of terminology rather than reality. A hydrogen atom without an electron is a proton, however, there are many circumstances where it is convenient to consider it as H⁺, it makes it easier to understand some chemical reactions.

[mxplxxx (OP)]

In that case you are hitting a problem of terminology rather than reality. A hydrogen atom without an electron is a proton, however, there are many circumstances where it is convenient to consider it as H⁺, it makes it easier to understand some chemical reactions.

Thx, but my question still stands. Are you saying physics uses poor terminology about this basic theory?

[Colin2B]

Not really.
Terminology evolves over time to suit purpose. So a chemist might refer to it as a H⁺, but a nuclear physicist might find it easier to think of it as a proton.
No problem, they are the same thing and as long as you keep that in mind there isn’t a real conflict.

[mxplxxx (OP)]

Not really.
Terminology evolves over time to suit purpose. So a chemist might refer to it as a H⁺, but a nuclear physicist might find it easier to think of it as a proton.
No problem, they are the same thing and as long as you keep that in mind there isn’t a real conflict.

So a hydrogen ion and a proton are identical. No chance a hydrogen ion contains more than a proton? Something to anchor a proton for example.

This raises the question, which of the following two statement is correct?

A hydrogen ion contains a proton.
A hydrogen atom is a proton.

[mxplxxx (OP)]

Not really.
Terminology evolves over time to suit purpose. So a chemist might refer to it as a H⁺, but a nuclear physicist might find it easier to think of it as a proton.
No problem, they are the same thing and as long as you keep that in mind there isn’t a real conflict.

So a hydrogen ion and a proton are identical. No chance a hydrogen ion contains more than a proton? Something to anchor a proton for example.

This raises the question, which of the following two statement is correct?

A hydrogen ion contains a proton.
A hydrogen atom is a proton.

from http://www.brooklyn.cuny.edu/bc/ahp/SDPS/PSLectNotes/SD.PS.LectP1.html

Isotopes
Isotopes are families of atoms that have the same atomic number but different atomic masses.
Key concepts:
hydrogen is an element with three isotopes.
the most common form of hydrogen (written in chemical notation as H) has a single proton at its center and no neutrons.
another form of hydrogen, called deuterium, has a single proton and single neutron.
a third form of hydrogen, called tritium, has a single proton and two neutrons.
the atomic substructure of tritium is unstable and is radioactive.

So it would appear a hydrogen ion and a proton are not identical, yet many time in physics I have read articles that seem to suggest they are.

[chiralSPO]

Very astute questions--I will attempt to clarify:

• ¹H is the simplest atom, consisting of only one proton and one electron. If the electron is removed, only the proton remains, so ¹H⁺ is exactly the same thing as a single, lone proton.

• There are two other isotopes of hydrogen: deuterium (²H or D), which contains one proton and one neutron in the nucleus, and tritium (³H or T), which contains one proton and two neutrons in the nucleus. ²H⁺ has the same charge as a single lone proton, but is also about twice as massive (which influences some things like reaction rates and tunneling), and has a nuclear spin of 1 (while ¹H⁺ has a nuclear spin of ½, so these ions are clearly distinguishable by NMR spectroscopy).

• The natural abundances of the isotopes of hydrogen are 99.98% ¹H, 0.02% ²H, and effectively 0% ³H (tritium is radioactive and decays with a half life of about 12 years). Thus, unless isotopes are specifically indicated, we can safely assume that "H⁺" is ¹H⁺ is a proton.

• There are atoms with multiple protons in the nucleus, (all of the periodic table except for hydrogen). But it would not be accurate to say that there are H⁺ ions in the nucleus. I was very careful above to say that H⁺ ions are "single lone protons" because, when combined with other nucleons (protons and neutrons are both called nucleons), the protons no longer have all the same properties--the interactions with the rest of the nucleus influence the effective mass of the nucleons, and the spin state of the "proton" must be considered in the context of the whole nucleus. It is also virtually impossible to remove a proton from a nucleus (a nucleus can emit a β⁺ particle and a neutrino to convert a proton in the nucleus into a neutron in the nucleus, and nuclear reactions can lead to emission of neutrons which then decompose into protons and electrons and neutrinos, but I am not aware of any radioactive decay that involves a proton being expelled*) In short, it is best to consider the nucleus as a unit, and think of the proton and neutron counts of the nucleus as good accounting tools, but it's probably best not to think of the nucleus as actually consisting of an aggregation of protons and neutrons.

*EDIT: I stand corrected--proton emission is a thing, but it only happens under extreme conditions (https://en.wikipedia.org/wiki/Proton_emission ). My point still stands: protons in the nucleus ≠ lone protons.

[evan_au]

So a hydrogen ion and a proton are identical. No chance a hydrogen ion contains more than a proton? Something to anchor a proton for example.

Perhaps part of the confusion comes from the difference between the conditions typically used by Physicists and Chemists:
- Physicists at the Large Hadron Collider strip the electron off a hydrogen atom, and inject the remaining positive proton into an extreme vacuum, guided by electric and magnetic fields. There is nothing physical for the proton to interact with (until it is smashed into another proton traveling the opposite direction at nearly the speed of light).
- Chemists typically take hydrogen which is part of a molecule (eg acetic acid), and dissolve it in water. Some of the hydrogen atoms lose their electron, becoming a positive hydrogen ion. (The electron is left with the remainder of the acetic acid molecule, which now becomes a negative ion). The hydrogen ion (which is a proton) is surrounded by around 50 or so water molecules, all oriented so their more negative oxygen side tends to face the proton's positive charge.

A chemist's "cluster of 50 water molecules+a proton (plus acetate? ions)" behaves very differently from the physicist's "proton in a vacuum".

[PmbPhy]

A proton on its own is not a hydrogen atom, you need to add an electron.

It can be thought of as an atom. A proton is a hydrogen ion which is a hydrogen atom with an electron missing.