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Chemistry / Re: What is the proton number in NH3 and NH4+?

« on: 24/07/2019 17:31:14 »

If you add a proton to the actual nucleus of a chloride ion (which has 17 protons and 18 electrons), it becomes an argon atom (with 18 protons and 18 electrons). However, if you don't combine nuclei, and just "stick" the proton "in" the electron cloud of the chloride it forms a molecules of hydrogen chloride (which has 18 electrons surrounding a nucleus with 17 protons and a nucleus with 1 proton.)

Cl^– + H⁺ → HCl (chemical reaction)
Cl^– + H⁺ → Ar (nuclear reaction)

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Chemistry / Re: What is the proton number in NH3 and NH4+?

« on: 24/07/2019 16:45:34 »

Could you explain this point in an easy way please 'each proton just has to be its own nucleus, ie a H+ ion.'?

The atom is bonded to a positive hydrogen ion.

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Chemistry / Re: What is the proton number in NH3 and NH4+?

« on: 24/07/2019 03:49:05 »

Like I said in another of your threads, the number of protons in a given element never changes. Nitrogen always has 7 protons, regardless of what molecule it is in or what its electric charge is. The number of protons is what defines the element. If the number of protons was different, it would no longer be nitrogen.

I also agree with you but I am confused about why N got positivie charge on it. As I know positive charge means proton. one positive charge means one extra proton. could you explain it, please?

Yes, protons have positive charge. But, as has been pointed out many times, changing the number of protons in the nucleus changes the identity of the element. Instead, electrons are exchanged between atoms. Any atom (or molecule) with an equal number of protons and electrons in it will be neutral, any atom (or molecule) with more electrons than protons will be negatively charged (magnitude of charge scales linearly with the difference is), and any atom (or molecule) with fewer electrons than protons will be positively charged (again magnitude of charge scales linearly with the difference is.)

Note that it is also possible to add one or more protons to an atom (or molecule) without changing the element. each proton just has to be its own nucleus, ie a H⁺ ion. Chemists and biologists will often talk about the "protonation state" of a species, meaning how many of theoretically exchangeable protons are still on there.

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Chemistry / Re: What is the proton number in NH3 and NH4+?

« on: 23/07/2019 22:24:29 »

Like I said in another of your threads, the number of protons in a given element never changes. Nitrogen always has 7 protons, regardless of what molecule it is in or what its electric charge is. The number of protons is what defines the element. If the number of protons was different, it would no longer be nitrogen.

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Chemistry / Re: How to find sigma and pi bond?

« on: 23/07/2019 12:09:55 »

The COOH part has a pi bond between the C atom and one of the O atoms. That is the fourth.

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Chemistry / Re: What is the proton numbers of carbon in CH3+?

« on: 23/07/2019 07:57:33 »

Carbon always has six protons. It wouldn't be carbon otherwise.

Now, how many electrons does carbon have in this state 5 or 6? and what is the hybridization state of carbon here SP^3 or SP^2?

If it has a +1 charge, then it has one fewer electron than normal, which would be 5. The methyl cation is isoelectronic with a single borane unit (BH₃), which has sp² hybridization.

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Chemistry / Re: In this reaction How many electrons carbon anion has?

« on: 23/07/2019 06:37:14 »

Where do the carbon get the extra electron for the negetive charge?

Presumably by taking it from some other atom before it became involved in the reaction that this thread is about.

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Chemistry / Re: What is the proton numbers of carbon in CH3+?

« on: 23/07/2019 06:33:15 »

Carbon always has six protons. It wouldn't be carbon otherwise.

The positive charge would be due to the carbon losing an electron somehow.

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Chemistry / Re: In this reaction How many electrons carbon anion has?

« on: 22/07/2019 16:53:53 »

H⁺ has no electrons (just one proton--this reaction is a "protonation")
There are a total of 10 electrons in CH₃^– (6 from the C atom, 1 for each of the 3 H atoms, and 1 extra electron for the negative charge.) Two of these electrons form the inner "core" of the carbon atom (a full 1s orbital), and the remaining 8 electrons are all in the "valence." We can think of there bing 2 electrons in each of the 3 C-H bonds, and another 2 electrons as a lone pair on C.

When the H⁺ comes close to the electrons in the lone pair, it will be attracted electrostatically, and will get closer and closer until it is trapped and "bonded." The product molecule, CH₄ is neutral and has 10 electrons (the proton didn't bring any electrons with it.) The mechanism can be represented by a single curved and double-headed arrow, pointing from the lone pair of the methyl anion (CH₃^– and going to the proton (H⁺).

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Chemistry / Re: How many protons and electrons of C and Cl are in this compound?

« on: 22/07/2019 15:38:18 »

Every H atom has 1 proton and 1 electron
Every C atom has 6 protons and 6 electrons
Every Cl atom has 17 protons and 17 electrons

These are all conserved when the atoms come together to form (neutral) molecules.

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Chemistry / Re: CH3+ and CH3- ions?

« on: 21/07/2019 10:44:53 »

https://en.wikipedia.org/wiki/Methyl_group#Methyl_cation

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Chemistry / Re: How to calculate the valency of 'Al' in 'Al2O3'?

« on: 05/10/2018 12:24:25 »

Do you know (or can you find out) the valency of oxygen?

Yes -2.3 = -6

OK, so what must the valency of the aluminium in the oxide be in order for the material to be neutral overall?

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Chemistry / Re: How to calculate the valency of 'Al' in 'Al2O3'?

« on: 05/10/2018 09:34:10 »

Even if you don't know the valency of oxygen, suppose the valency of Al is x and O is y, then you need the simplest integer solution to 2x = 3y, which is obviously x = 3, y = 2.

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Chemistry / Re: Why NO₂- ion got the negative charge?

« on: 17/09/2018 16:43:49 »

From the associated cation. If you take the case of nitrous acid then it takes it from the hydrogen, or for sodium nitrite then it takes it from the sodium.

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Chemistry / Re: Why NO₂- ion got the negative charge?

« on: 16/09/2018 17:38:47 »

In order to have the octet of each atom filled, an extra electron is required. Here is a website that shows the structure of the nitrite ion. Count the number of valence electrons that each atom contributes: https://chemfiesta.org/2015/09/18/resonance-structures/

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Chemistry / Re: Why are the half-filled and fully filled orbitals more stable?

« on: 09/09/2018 21:46:54 »

The exchange benefit comes whether the orbital is filled or not.

If all p orbitals are half filled, then there are 3 equivalent electrons (one in each p orbital, and all with the same spin, let's say it's "up"). If all the p orbitals are filled then there are two sets of 3 equivalent electrons (the three "up" electrons can exchange, and the three "down" electrons can exchange.)

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Chemistry / Re: How to find the equivalent weight?

« on: 05/09/2018 19:37:35 »

It is an acid/ base reaction.
A proton is transferred, which is pretty much the definition.

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Chemistry / Re: How to find the equivalent weight?

« on: 05/09/2018 05:39:48 »

So, which compounds take part in oxidation-reduction reactions?

Any compound can take part in an oxidation-reduction reaction as long as the result of the reaction is a change of the oxidation state of the atoms present. In order to know if an oxidation state has been changed, you need to be able to count how many electrons "belong" to particular atoms. If an atom gains electrons, then it has been reduced. If it loses electrons, it has been oxidized. For example, take the following reaction:

2Ca + O₂ → 2CaO

In this reaction, the two calcium atoms and the two oxygen atoms start out with an oxidation state of zero because they are neutral. After the reaction, the calcium atoms have lost electrons to the oxygen atoms, forming Ca²⁺ and O^2-. Since the calcium atoms lost electrons, they were oxidized. Since the oxygen atoms gained electrons, they were reduced.

and what's the name of this reaction?

It's an acid-base reaction. An acid is a substance that donates protons whereas a base is a substance that accepts protons. More specifically, that is the definition of a "Bronsted acid" or a "Bronsted base".

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Chemistry / Re: If I break H2SO4, what should I get?

« on: 03/09/2018 03:39:26 »

If I break H2SO4, we get 2H⁺ and SO₄²⁻. Is it possible to write the same form in a different way such as 2H⁺ to H⁺⁺ and SO₄²⁻ to 2SO₄⁻? Do they mean the same thing?

I'm afraid not. The number in front of the chemical symbol is a statement of how many moles of the substance there are. In order to keep the equation balanced, the total number of moles of each atom much remain constant. Changing the charge is also not equivalent. H⁺ means that the hydrogen atom has a net charge of +1. Changing that to H⁺⁺ or H²⁺ would mean that you are increasing the net charge on the ion from +1 to +2, so that it is no longer the same kind of ion. In fact, hydrogen cannot have a charge greater than +1, since it is a bare nucleus and as such has no more electrons that it can lose.

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Physics, Astronomy & Cosmology / Re: How to find the velocity?

« on: 01/09/2018 11:33:29 »

A totally different approach, which needs a lot less calculus:
When I see the (x,y) position of an object described as (x=a*sin(ωt), y=a*cos(ωt) ), I deduce that we are seeing an object which is in a circular orbit around the origin = (0,0).

Now, a circular orbit is:
(1) not moving towards the origin
(2) and it's not moving away from the origin
(3) And the velocity is not moving in the same direction as the line from the origin to the point, which is the same as (2)
(4) in fact, the velocity is moving at right-angles (perpendicular) to the line from the origin to the point. This is what continually bends the path around in a circle.

Whether a qualitative answer like this will make the examiner happy is another story!