Pages

Thursday, April 2, 2009

Homework 1 (due before 6th April 2009)

Dear 1CH304,

Critically comment the following quote:

"A An atom is a very small particle. It is able to be divided into smaller particles, known as protons, neutrons and electrons. These particles are sub-atomic particles and are the smallest particles of an atom. In addition, the atoms of an element are always identical. While the valence electrons of an atom are always degenerate. The chemical property of an atom is largely determined by the protons of the atom."

There are 5 errors in the above quote. Quote the relevant sentences and explain the error(s).

You may wish to this and/or that as resource materials to answer this question.

Suggested Answer
.... are the smallest particles of an atom

(1) This is not true as we have learned that protons, electrons and neutrons can be subdivided. However, we don't need to know the details.

the atoms of an element are always identical

(2) The existence of isotopes refute this statement. For example, the element hydrogen has 3 isotopes, 1H, 2H and 3H.

..valence electrons of an atom are always degenerate

(3) Degenerate means that the valence electrons are found on the same energy level. That is not true. Using oxygen as an example, it has 6 valence electrons. It's electronic configuration is 1s22s22p4. The 6 valence electrons are found on 2s and 2p. Clearly, 2s and 2p are of DIFFERENT energy levels.

..chemical property of an atom is largely determined by the protons of the atom

The above statement has two errors:
(4) It is the valence electrons of an atom that determines its chemical property.

(5) The protons and neutrons (hence the nucleus) affects the physical property.

Comments

Generally there are many good answers! I am pleased and I am confident we can expect better ones in the future. However, the accuracy of the explanation was quite weak.

(1) Atoms are very small particles. The atomic radius is close to 10-9 m, it is indeed very small!

(2) There are a few who struggled in their explanation of degenerate. The orbital in a subshell are degenerate, however two subshells are not degenerate. Interestingly, there are a few who did not know the meaning of degenerate.

(3) Some have left out the explanation and hence their answers were marked down as it did not adhere to the requirement of the question.

23 comments:

Chatterbox said...

"They are able to be divided into smaller particles, known as protons, neutrons and electrons."

This is not completely true as, electrons itself cannot be exactly called as a particle. But rather it can assume the form of a particle and a wave, hence the statement that says it is a smaller "particles" is not completely true.

"These particles are sub-atomic particles and are the smallest particles of an atom."

This is not really true because there are quarks that made up protons and electrons. Even though the statement itself is not completely wrong, as the quark theory will only apply when the question said smallest indivisible particle. The statement above may still be accepted in A level in the context that it says the smallest particle. (if i am not wrong >.<)

"In addition, the atoms of an element are always identical."

There are isotopes so this is also a mistake.

"While the valence electrons of an atom are always degenerate."

Not true, because the valence electrons itself are located in different subshells and orbitals with different energy levels.

" The chemical property of an atom is largely determined by the protons of the atom."

Not true as it is the electrons that are more prominent in determining the chemical property of an atom and it's magnetic properties.

Ren_aldy

Sam said...

1. "A atom a very small particle." Its a grammatical error though. Anyway, its suppose to be "AN atom IS a very small particle."

2. "These particles are sub-atomic particles and are the smallest particles of an atom." Its a common misconception that the subatomic particles are the smallest particles of an atom. However, as mentioned in your previous tutorial(if I remembered correctly), the sentence should be changed to "These particles are known as sub-atomic particles and are the smallest non-divisible particles of an atom." as there are photons and such that exist.

3. "In addition, the atoms of an element are always identical." This sentence is not true as there are cases where the atoms of an element is not identical since there are varied number of neutrons in the nucleus of the atoms. These are known as Isotopes. Hence, the sentence should be corrected to "In addition, the atoms of an element are not always identical, as some elements if not all of the elements have isotopes whereby the nucleus of the atoms differ in the number of neutrons for the same element."

4. "While the valence electrons of an atom are always degenerate." Okay, this sentence just somehow doesnt make sense to me. Rather, the sentence(in my opinion) should be "All orbitals in a subshell are always degenerate." Now, this makes more sense as it shows that all the orbitals (e.g. Px, Py and Pz) have the same energy level in a subshell(P).

5. "The chemical property of an atom is largely determined by the protons of the atom." This, is nonsense. The chemical property of an atom is dependent on the transfer and redistribution of electrons! Thus, the correct sentence will be "The chemical property of an atom is largely determined by the electrons of the atom."

I think there's still mistakes in my comments though =/

Jo said...

"In addition, the atoms of an element are always identical."

Not all atoms of an element are always identical, because there are isotopes, which have different number of neutrons. Thus not all atoms are identical.

Brandon said...

Edit 2:

“atoms of an element are always identical.”
Atoms of an element can differ as they can exist as isotopes, with identical number of protons but a different number of electrons in the nucleus of the atom [however most isotopes are unstable and fall apart during radioactive decay process]. This results in a variation of mass number, thus an average of the masses of the different isotopes is taken used as the relative atomic mass. (E.g. Chlorine-35 and Cholrine-37. Thus Chlorine has a RAM of 35.5)

“The chemical property of an atom is largely determined by the protons of the atom”
Often, the property of an atom is determined by the valence electrons found in the outer shell. This would result in a difference in reactivity of the atom. The reactivity is affected by the outer shell as the atom would be more reactive with 1 or 7 valence electrons as they want to form the stable octet structure as soon as possible.

“valence electrons of an atom are always degenerate”
Electrons( I corrected this) in different subshells have different energy levels. Hence only when the electrons are in the same subshell are they degenerate. This is due to the different energy of the different subshells which results in the order being filled. (From the least energy to highest energy) As the outermost quantum shell can have more than one subshell, the valence electrons of an atom would not be degenerate.

“These particles are sub-atomic particles and are the smallest particles of an atom”
Taken from WikiAnswers: Of the three basic particles that atoms are made of, the electron is the smallest. But there are smaller subatomic particles. There are a lot of them, actually. So many in fact that there is a particle zoo. If we look in the zoo for the smallest subatomic particle, we might find that the quark is a likely candidate. Even smaller is the string, which, though not a particle, may be the fundamental building block of matter.
Thus these are not the smallest particles of an atom. However, in our syllabus they are regarded as the smallest particle of an atom for simplicity sake. Hence these subatomic particles can be broken down further to even smallest subatomic particles. ( Protons and neutrons into quarks)

(I’m not sure of this point)
“They are able to be divided into smaller particles, known as protons, neutrons and electrons.”
Atoms are not divided into smaller particles as division of an atom would result in nuclei fission (production of nuclear energy). Hence divided is not the right term and it should state that an atom consists of smaller particles known as protons, neutrons and electrons.

Abbie said...

#1. "It -an atom- is able to be divided into smaller particles, known as protons, neutrons and electrons."

Atoms are the basic unit of matter and cannot be further divided. They consist of a nucleus, made up of protons and neutrons. Electrons circulate round the nucleus.

#2. " the atoms of an element are always identical."

Atoms of an element need not be identical. In the case of isotopes [eg hydrogen], the atoms have the same proton number but different nucleon number.

#3. "valence electrons of an atom are always degenerate"

Degenerate refers to having the same energy. One or more corresponding orbitals in a subshell have the same energy. Therefore, electrons in the corresponding orbitals in a subshell are degenerate. However, in the valence shell, more than one subshell is present. Hence, not all valence electrons are degenerate.

#4. "chemical property of an atom is largely determined by the protons of the atom"

The chemical property of an atom is largely determined by the valence electrons of the atom. Valence electrons of an atom governs the bonding of an atom.



#5. “These particles are sub-atomic particles and are the smallest particles of an atom”

In the Standard Model of physics, both protons and neutrons are composed of elementary particles called quarks. Quarks are a type of elementary particle and major constituents of matter. They combine to form composite particles called hadrons, the most well-known of which are protons and neutrons. Hence, protons and neutrons are not the smallest particles of an atom

clare said...

Mr kwok, my answers are shown as "...".
1.An atom is the "smallest indivisible unit of a particle.”
2.It is able to be divided into smaller particles, known as protons, neutrons and electrons.These particles are sub-atomic particles and are the "smallest particles of an atom that retain the chemical identity of the element.”
3. In addition, the atoms of an element are always identical. – This is not true as the atoms of an element can have varying neutrons,thus affecting the size of the nucleus(e.g, 35Cl and 37Cl).
4. While the valence electrons of an atom are always degenerate. – “Valence electrons do not degenerate, they are donated to other elements to achieve the stable electronic configuration."
5.The chemical property of an atom is largely determined by the protons of the atom.– "the chemical property of an atom is largely determined by the number of electrons the element has."

Scwj said...

Why this quote is wrong( I think ):

1:" A atom a very small particle "

This is a very vague statement. A "very small particle" can refer to many, many things, as it is arbitrary. A dust particle, for instance, can be a "very small particle". Rather, the correct definition of an atom is "a basic unit of matter", which should be used to avoid controversy.

2."These particles are sub-atomic particles and are the smallest particles of an atom"

The validity of this quote depends on how critical one is. Strictly speaking, neutrons, protons and electrons are not the smallest indivisible particles of an atom. For example, protons and neutrons are made up of even smaller particles known as quarks.

However, if one does not look too deeply into the matter, then yes, for layman purposes these particles are indeed the smallest particles in an atom.

3. "In addition, the atoms of an element are always identical."

This is false. The atoms of an element can exist in the form of isotopes- atoms with the same number of protons but a different number of neutrons. Hence, due to this difference in the number of particles in the nuclei, the atoms of a given element are not always identical.

4. " While the valence electrons of an atom are always degenerate."

This should be false. Take for example an element with 6 valence electrons, which fills up the sub-shells of ns np in the form of ns^2 and np^4. As the p sub-shell has a higher energy level as compared with the s sub-shell, the valence electrons occupying the orbitals in the p sub-shell would have a higher energy level than those occupying the s orbital. This can be explained because the np sub-shell would be further away from the nucleus than the ns sub-shell, and hence, causes the np sub-shell to experience less forces of attraction from the nucleus, resulting in greater energy levels.

Due to this difference in energy level between the valence electrons, they are not degenerate.

5. " The chemical property of an atom is largely determined by the protons of the atom"

This is a farcical statement. The chemical properties of an atom is largely determined by the number of valence electrons it possesses, not the number of protons in it. Due to this, elements with the same number of valence electrons exhibit similar chemical properties.

----

Regards,

Chia Wei Jie

Tim K said...

"It is able to be divided into smaller particles, known as protons, neutrons and electrons."
This quote neglects to mention that there is an exception. The Hydrogen-1 atom does not contain any neutrons.

"These particles are sub-atomic particles and are the smallest particles of an atom."
Protons, electrons and neutrons can be further divided into smaller particles known as quarks.

"In addition, the atoms of an element are always identical."
Isotopes of elements exist. These are different types of atoms of the same element, which contain different numbers of neutrons (and therefore also a different relative atomic mass).

"While the valence electrons of an atom are always degenerate."
The valence electrons of an atom may not necessarily come from orbitals in the same subshell. Therefore, the atom’s valence electrons may have different energy levels.

"The chemical property of an atom is largely determined by the protons of the atom."
An atom’s chemical properties are largely determined by its electrons, not by its protons.


-Timothy Kwok

nick lum said...

"The chemical property of an atom is largely determined by the protons of the atom."
--not entirely correct. the electrons and neutrons play a part too.

"In addition, the atoms of an element are always identical."
--incorrect. isotopes exist, thus not every single atom is alike, even for the same element.

"These particles are sub-atomic particles and are the smallest particles of an atom."
--partially incorrect. these are indeed sub-atomic particles but they are not the smallest known particles.

"An atom is a very small particle."
--expression error. an atom is not only very small, it is miniscule; smaller than the wavelength of visible light.

"While the valence electrons of an atom are always degenerate."
--incorrect. valence electrons can be of different subshells, meaning different energy levels.

Xiaomin said...

"These particles are sub-atomic particles and are the smallest particles of an atom. " - This is incorrect because they are not the smallest particles known in the atom.

"the atoms of an element are always identical" - This is incorrect due to the presence of Isotopes. Isotopes are atoms of the same element with the same number of protons but different number of neutrons. Hence, it is incorrect to suggest that the atoms of an element are always identical.

"The chemical property of an atom is largely determined by the protons of the atom" - This is incorrect because the chemical property of an atom is largely determined by the number of ELECTRONS not PROTONS of the atom.

"It is able to be divided into smaller particles, known as protons, neutrons and electrons" - The word divided is used in a wrong context. Instead, the word "categorized" should be used. The word divided seems to suggest that the atom can be separated into neutrons, protons and electrons, which is incorrect, because an atom is uncuttable, something that cannot be divided further.

"In addition, While the valence electrons of an atom are always degenerate." - This is incorrect as only p Atomic Orbitals for the same n (principal quantum number) are degenerate.

Anonymous said...

'the smallest particles of an atom.' The sub-atomic particles in an atom are not the smallest particles in an atom. 'atoms of an element are always identical.' Not all atoms in an element are the same; for example isotopes which are atoms with differing no. of neutrons. 'valence electrons of an atom are always degenerate' This is dependent on the orbitals in which the valence electrons are in. If they share the same subshell, then they are degenerate."The chemical property of an atom is largely determined by the protons of the atom." The chemical properties are in fact dependent upon the transfer and redistribution of electrons and thus the no. of electrons, not protons.
-kev

Chooijingyew said...

'It is able to be divided into smaller particles, known as protons, neutrons and electrons'.

An atom cannot be divided. The word comes from the Greek word atomos, which means something that cannot be divided further. While atoms consist of other particles, the atom itself cannot be divided.

'These particles are sub-atomic particles and are the smallest particles of an atom'.

The smallest particles of an atom are quarks and leptons. Protons are composed of two up quarks (electrical charge of +2/3 each) and one down quark (electrical charge of -1/3 each) while neutrons are composed of one up quark and two down quarks.

'In addition, the atoms of an element are always identical'.

Atoms of an element may have different numbers of neutrons. These are called isotopes.

'While the valence electrons of an atom are always degenerate'.

Valence electrons do not always have the same energy. An electron in an s-subshell would be at a different energy level compared to an electron in a d-subshell.

'The chemical property of an atom is largely determined by the protons of the atom'.

Chemical properties of atoms are determined by the valence electrons of the atom. This is because the valence electrons are involved in chemical bonding, not the protons. This is shown in the periodic table where elements in the same groups (and therefore having the same number of valence electrons) have similar chemical properties.

Dang Ngoc Dung said...

1. "An atom is a very small particle"
--> Not precise
--> An atom is the smallest particel of an element that retain the chemical identity of the element.

2. "These particles are sub-atomic particles and are the smallest particles of an atom"
--> protons and neutrons can be further divided in to smaller particles called quarks

3. "the atoms of an element are always identical"
--> isotopes are atoms of an element, containing the same number of protons but different numbers of neutrons in the nuclei.

4. "the valence electrons of an atom are always degenerate"
--> an atom can either gain or lose its valence electrons to achieve the noble gas configuration

5. "the chemical property of an atom is largely determined by the protons of the atom"
--> it is the valence electrons that determine the chemical property of an atom as they determine which bonds to form with which atom/molecule.

Benjamin said...

Hmwk 1

"An atom is a very small particle"
This statement is not specific enough. we all know that atoms are really tiny particles. It should be "an atom is the smallest particle of an element that still retain the checmical identity of the element."

"In addition, the atoms of an element are always identical. "
This statement is purely incorrect as we know that every element have at least one isotope, which has a differing number of neutrons in the nucleus.

"While the valence electrons of an atom are always degenerate."
This statment is wrong as in realtiy, the valence electrons have different energy levels due to their position on the different shells. for example, the ionization enrgy of an electron closer to the nucleus is higher than one in the othermost shell.

"The chemical property of an atom is largely determined by the protons of the atom."
this statment is entirely mistaken as the checmical property of an atom is determined by the number of valence electrons in the other most shell. the intesity of the checmical reaction depends on the number of shells/obitals that is completely filled up with electrons.


Sorry sir. thats all i could find. i could not find the fifth mistake in the paragraph.

benjamin
1sc1
ACJC

STORM-A-SAURUS said...

"These particles [protons, neutrons and electrons]... are the smallest particles of an atom."

This implies that protons, neutrons and electrons are of equal masses and sizes but protons and neutrons are similar in mass and size whereas electrons are 1840 times smaller than a proton/neutron.


"These particles ... are the smallest particles of an atom."

Protons, neutrons and electrons of an atom are made up of even smaller particles known as quarks. Quarks have electric charge values in fractions, such as positive two-thirds and negative one-third.


"In addition, the atoms of an element are always identical"

Isotopes of an element exist where the atoms of the same element have the same number of protons but a different number of neutrons.


"While the valence electrons of an atom are always degenerate."

The valence electrons of an atom may be from different subshells (for example the s-subshell and p-subshell) despite being in the same quantum shell (having the same principal quantum number).

As the energy levels of the subshells differ (the electrons in the p-subshell are more energetic than the electrons in the s-subshell of the same quantum number), the valence electrons do not have the same amount of energy, and are therefore not degenerate.


"The chemical property of an atom is largely determined by the protons of the atom."

Chemical properties of atoms are determined by the electrons in the atom. This is because the electrons of the atom, not the protons, are involved in bonding in chemical reactions.

Crystal said...

1. "These particles are sub-atomic particles and are the smallest particles of an atom."

Sub-atomic particles are not the smallest particles of an atom as there are quarks which make up the protons and neutrons.

2. "In addition, the atoms of an element are always identical."

Atoms of an element are not always identical, such as in the case of isotopes, which are atoms of the same element (same number of protons) with diferring numbers of neutrons.

3. "While the valence electrons of an atom are always degenerate."

It's the orbitals of the same subshell that have the same energy (degenerate).

4. "The chemical property of an atom is largely determined by the protons of the atom."

The chemical property of an atom is largely determined by the electrons of the atom.

Sorry Mr Kwok, I couldn't identify the last error.

Unknown said...

Errors:

1. It is able to be divided into smaller particles, known as protons, neutrons and electrons.

- An atom is indivisible. It is not divided into sub-atomic particles, it is made up of sub-atomic particles.

2. These particles are sub-atomic particles and are the smallest particles of an atom.

- Protons and neutrons are made up of smaller theoretical particles called quarks.

3. In addition, the atoms of an element are always identical.

- There are atoms of the same element which contain the same number of protons but different number of neutrons. These atoms are known as isotopes.

4. While the valence electrons of an atom are always degenerate.

- Valence electrons of an atom are not degenerate if they do not belong to the same type of orbital.

5. The chemical property of an atom is largely determined by the protons of the atom.

- The chemical property of an atom is largely determined by the number of valence electrons in the atom.

Ian Lee said...

"It is able to be divided into smaller particles" - Unable to be divided further into smaller particles

"The chemical property of an atom is largely determined by the protons of the atom." - Determined by electrons, not protons

"These particles are sub-atomic particles and are the smallest particles of an atom." - Not smallest, smaller ones like qwerks (sp) exist

"The atoms of an element are always identical." - Not always identical

"While the valence electrons of an atom are always degenerate." - Not always degenerate as valence shells have numerous subshells and the subshells have different energy levels

-IAN LEE RUI JIE

yauwan said...

1.
"...and are the smallest particles of an atom."
- protons, neutrons and electrons are not the smallest particles as for example, protons and neutrons are composed of theoretical particles called quarks in which are smaller.

2.
"...the atoms of an element are always identical."
-atoms of an element are not always identical as there each element would have at least one isotope in which they have different number of neutrons

3.
"...valence electrons of an atom are always degenerate."
-valence elctrons of an atom are not always degenerate as when there are more than 1 subshell in the quantum shell, the electrons are no longer degenerate.

4.
"The chemical property of an atom is largely determined by the protons of the atom."
-rather, the chemical prperties of an atom are largely determined by the number of valence electrons and and number of quantum shells.

5.
"An atom is a very small particle."
-atoms are not particles. rather they are conceptualised as wave-like packets and its properties only as probabilities.

Unknown said...

Hi Mr. Kwok, here is my answer:

1. "It is able to be divided into smaller particles, known as protons, neutrons and electrons."

The term "divided" is inappropriate as atoms are not exactly divided into smaller particles, that is nuclear fission. They are merely made up of protons, neutrons and electrons.

2. "These particles are sub-atomic particles and are the smallest particles of an atom."

Protons, neutrons and electrons are not the smallest particles of an atom. There are other smaller subatomic particles, eg. protons and neutrons can be broken down into quark

3. "In addition, the atoms of an element are always identical."

Atoms of an element are not always identical. An element may have several isotopes (atoms with the same number of protons but different number of neutrons) An example would be Chlorine-35 which has 18 neutrons, 17 protons and Chlorine-37 which has 20 neutrons, 17 protons)

4. "While the valence electrons of an atom are always degenerate."

Valence electrons of an atom are not always degenerate. Electrons in different subshells have different energy levels and different ionisation energies, hence, only valence electrons in the same subshells are degenerate.

5. "The chemical property of an atom is largely determined by the protons of the atom."

The chemical property of an atom is not largely determined by the protons of the atom but by its valence electrons.

Johanan said...

1)“These particles are sub-atomic particles and are the smallest particles of an atom” The protons and neutrons are not the smallest indivisible particles of an atom. Protons and neutrons are made up of smaller elementary particles known as quarks.

2)“In addition, the atoms of an element are always identical.” Atoms of an element are not necessarily identical; isotopes (Atoms with the same number of protons but different number of neutrons) exist.

3)“While the valence electrons of an atom are always degenerate “The valence electrons of an atom are not always degenerate. Electrons in the same subshell are degenerate. However, in the case where the valence shell has more than one subshell, (ns,np), the electrons are no longer degenerate since there are different subshells present in the one principle quantum shell.

4)“The chemical property of an atom is largely determined by the protons of the atom." The chemical properties of an atom are determined by the electrons of the atom rather than the electrons as it is the interactions between the electrons that give rise to the chemical properties (c.f. bonding)

5)“It is able to be divided” Atoms cannot be divided further? Or at least it would be extremely difficult to.

6)“… particles, known as protons, neutrons and electrons” Electrons do not exist as particles but rather due to the wave-particle duality nature of electrons, the exact location of a electron cannot be determined and this they cannot be classified as a particle at a specific point or location.

shagar said...

1. The atoms of an element are not always identical, they do differ in the form of isotopes with a different number of nuetrons, thus resulting in different nucleon numbers.

2. The valence electrons are not always degenerate, within the principal quantum shell, there are sub-shells with different energy levels.

3. The chemical property of an atom is determined by mainly the valence electrons.

4. Protons, neutrons and electrons, the sub-atomic particles are not the smallest particles of an atom.

5. The sub-atomic particles are not entirely particles, they exist as particles and waves and display both types of properties?

*5. An atom is unable to be divided into neutrons and protons and electrons, they are merely made up of those sub-atomic particles.

eileen said...

1. “An atom is a very small particle.“

An atom is the smallest particle of an element.

2. “These particles are sub-atomic particles and are the smallest particles of an atom. “

The protons, neutrons, and electrons are not the smallest particles and can be sub-divided further in to smaller particles like quarks.

3. “In addition, the atoms of an element are always identical.“

The atoms of an element are not identical as there are different isotopes of an element, where these isotopes have have atoms with the same number of protons and electrons but a different number of protons, and are therefore not identical.

4. “While the valence electrons of an atom are always degenerate.”

The valence electrons are not always degenerate as there are special cases for elements such as copper and chromium, where the valence electrons will be split into the 3d and 4s orbitals due to the 3d and 4s orbitals being very close in energy level, therefore it is ambiguous and priority is given to fill the 4s orbital over the 3d orbital as the 3d orbital is extremely unstable if not completely filled. Thus, the valence electrons will not be degenerate as there will be some electrons in 3d and some in 4s, orbitals with different energy levels.


5. “The chemical property of an atom is largely determined by the protons of the atom.”

This sentence is incorrect as the chemical properties of an atom of a particular element is determined largely by its number of valence electrons, which in turn determines the group in which it is placed in in the periodic table. Elements in the same groups have similar chemical properties, therefore the chemical properties of an atom is largely determined by its electrons.