Chemistry --- Elements,Compounds and Mixtures

baiyun SG

Please help. Thank you.

Molecules may be made up of atoms of the same element or atoms of different elements.

As defined in Chemistry Matters, a compound as a pure substance that contains two or more elements chemically combined.

I am confused, from some of the examples; I noticed that a compound is made of a combination of different elements. Are there examples of compounds with a combination of the same element ie two or more elements of the same type chemically bonded together?

UltimaOnline SG

Please help. Thank you.

Molecules may be made up of atoms of the same element or atoms of different elements.

As defined in Chemistry Matters, a compound as a pure substance that contains two or more elements chemically combined.

As long as it contains more than one element, it's called a compound.

Eg. Diamond is an allotrope of an element of carbon. Graphite is another allotrope of an element of carbon. Diamond and graphite are not compounds.

Eg. Water H2O is a compound of hydrogen and oxygen. Hydrogen peroxide H2O2 is another compound of hydrogen and oxygen.

Baiyun, go ahead and post examples here, and I'll tell you if they are compounds or non-compounds (ie. pure elements).

baiyun SG

As long as it contains more than one element, it's called a compound.

Thank you for your fast reply.

In this case, what does more than one element mean?Does it refer to different elements?

Can a compound be formed by more than one element of the same kind?

boboko SG

Examples of elements: Carbon, Hydrogen, Oxygen, Sodium, Potassium.

More than one element refers to different elements.
E.g. We cannot say Oxygen gas (O2) consists of 2 oxygen element (wrong!!!), but 2 oxygen atoms form oxygen gas.

Element is not a quantitative term and all elements are different (because of their proton number -> A level syllabus).

Et1j 12 SG

Compound – must be made up of two or more same atoms or different atoms throught covalent or ionic bond.

eg for compound that make up of two same atoms (hydrogen H2, Oxygen O2)

baiyun SG

Compound – must be made up of two or more same atoms or different atoms throught covalent or ionic bond.

eg for compound that make up of two same atoms (hydrogen H2, Oxygen O2)

Two same atoms chemically bonded together ----- Isn't this a molecule not a compound?

Please help to clarify.Thank you.

TTFU SG

A molecule may consist of atoms of a single chemical element, as with oxygen (O₂), or of different elements, as with water h20.

TTFU SG

eg for compound that make up of two same atoms (hydrogen H2, Oxygen O2)

Two same atoms chemically bonded together ----- Isn't this a molecule not a compound?

Please help to clarify.Thank you.

I dont think o2 is a compound. Its a molecue. Why is it a molecue ? cause it has 2 oxygen atom, For more info, you can check out wikipedia.

UltimaOnline SG

O2, molecular oxygen, is obviously NOT a compound.

UltimaOnline SG

To be precise O2 is known as dioxygen, the most common allotrope of the element oxygen.

Other well-known allotrope of oxygen is ozone (aka trioxygen).

UltimaOnline SG

When WhiteCloud made her/his latest post on the Primary 6 Question, I noticed I missed out on answering one of her/his previous questions.

You appear to have a confusion about "molecule" vs "compound", in your statement above.

A molecule can be either of an element, or of a compound. Atoms on the other hand, can only be of elements.

Eg1. O2 is a molecule of the element oxygen.

Eg2. H2O is a molecule of the compound water, aka hydrogen hydroxide, aka dihydrogen monoxide, aka hydrogen(I) oxide. (Consisting of two elements - hydrogen and oxygen).

Out of curiosity, is WhiteCloud a tutor or concerned parent, in asking these questions?

baiyun SG

Hi UltimaOnline

Thank you for your reply.

I am a parent.

Interesting, what makes you think I am a tutor?

Best wishes

UltimaOnline SG

Hi UltimaOnline

Thank you for your reply.

I am a parent.

Interesting, what makes you think I am a tutor?

Best wishes

Hi baiyun,

In addition to students, parents and tutors also seek help on homework questions in this forum. A parent would have been my first guess, a tutor second, because your maturity as expressed by your written style makes you unlikely to be a student (if you were one, you'd probably be a tertiary student, eg. in the Uni; but since you asked a secondary school chemistry question, this probably rules you out as a student, and therefore more likely a parent instead). Your child is in secondary 1 this year?

Out of curiosity (and only if you don't mind sharing), what is your own personal qualification? In the area of Arts, Science or Commerce? If Science, which of the 3 sciences?

I'm curious because you gave a very well written answer to the physics/biology questions in this thread, but at the same time in this current thread (ie. on this page), you appeared to have some confusion on fundamental chemistry principles. No offence intended, I'm just genuinely curious as to this puzzling observation.

baiyun SG

Hi UltimaOnline

My kid is in Sec One.

I've asked this particular question, so I’ve to read up so as to gain a better understanding.

Best wishes