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Syllabus
Syllabus
The relative electrical charges of the particles in atoms are:
Students should be able to use the nuclear model to describe atoms.
Atoms are very small, having a radius of about 0.1 nm (1 x 10-10 m).
The radius of a nucleus is less than 1/10 000 of that of the atom (about 1 x 10-14 m).
Almost all of the mass of an atom is in the nucleus.
The relative masses of protons, neutrons and electrons are (right):
What does this mean?
What does this mean?
What are subatomic particles?
What are subatomic particles?
Sub-atomic means smaller than an atom.
There are dozens of sub-atomic particles but at GCSE we worry about 3:
Protons, Neutrons and Electrons.
Not all are found in the same part of the atom.
The centre of the atom is the nucleus - it contains almost all the mass of the atom and all the "heavy" particles (Protons and Neutrons).
The electrons have almost no mass and are found far from the nucleus in shells.
As their name suggests, neutrons are neutral and have no electric charge.
Equally obviously, Protons are Positively charged (+1)
And since atoms have no overall charge, this tells us that ele
ctrons must be negative (-1)
The AQA syllabus is happy for us to treat the relative mass of the electron as 0, provided that we know it is not exactly 0.
In other words, it's too small to matter even though it can be measured.
And since all the "heavy" subatomic particles (neutrons and protons) are in the nucleus that means that almost all the mass of the atom is in the nucleus.
How big is an atom?
How big is an atom?
Really small is a good answer - but not good enough for a GCSE examiner.
They are happy for you to say that atoms have a radius of about 0.1 nm (1 x 10-10 m).
But that doesn't help most pupils in Year 9.
We know that there are 100 cm in a metre so 1cm is one hundredth of a metre = 1/100 m, which we can write in Standard form as 1x10-2 m
We know that there are 1000 mm in a metre so 1mm is one thousandth of a metre = 1/1,000 m, which we can write in Standard form as 1x10-3 m
A nanometer (nm) is one billionth of a metre 1/1,000,000,000 m, which we can write as 1x10-9 m
The radius of a typical atom is about 1/10 nm or 1x10-10 m
How big is a nucleus?
How big is a nucleus?
Really really small is a good answer - but that's not good enough for a GCSE examiner either.
They want you to know that the nucleus is about 1/10,000 the size of the atom.
So, if an atom has a radius of about 1 x 10-10 m, a nucleus must have a radius of 1 x 10-14 m.
If you don't really understand standard scientific notation for number yet, don't worry.
You'll do them in Maths eventually.
For now, you could just learn that atoms are around 0.1 nm and nuclei are 10,000 times smaller
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