Homework
Private study work (bring notes to show me next lesson) ;
• Read pages 6 – 7 in your text book and complete the practice questions on each double page spread
• Look at the following websites
• http://www.chemguide.co.uk/atoms/prope rties/gcse.html#top
• http://www.chemnotes.org.uk/f321.html
• Topic 1, concentrate on atomic structure

Look at the information below.
What does it tell you?
Write down anything you can think of.
35
17
Cl
37
17
Cl
35.5
17
Cl
37
17
Cl
-1
24
11
Na
+1

Sunday, 12 April 2020

Atomic Structure
• (a) describe protons, neutrons and electrons in terms of relative charge and relative mass;
• (b) describe the distribution of mass and charge within an atom;
• (c) describe the contribution of protons and neutrons to the nucleus of an atom, in terms of atomic (proton) number and mass (nucleon) number;
• (d) deduce the numbers of protons, neutrons and electrons in:
– (i) an atom given its atomic and mass number,
– (ii) an ion given its atomic number, mass number and ionic charge;
• (e) explain the term isotopes as atoms of an element with different numbers of neutrons and different masses;

Remember this is a model. It is the nuclear model of an atom.
Nucleus contains protons and neutrons
ELECTRON – negative (-1), mass
1/2000 (so small compared to the nucleus we say it is negligible).
Occupy shells around the nucleus
NEUTRON – neutral (0), same mass as proton (“1”)
-
-
+
+
PROTON – positive (+1), same mass as neutron (“1”)
Draw a labelled diagram for the structure of the atom.
This can be any atom or just a generic diagram.

Relative mass Relative charge Subatomic particle
Proton 1 +1
Neutron electron, e -
1
1/2000
0
-1

If you imagine an atom being the size of Wembley stadium, the nucleus would be about the size of a football on the centre spot.
The electrons would be two peas flying around the whole stadium. The rest of it: emptiness.

Protons, neutrons and electrons are not evenly distributed in an atom.
The protons and neutrons exist in a dense core at the centre of the atom. This is called the nucleus .
The electrons are spread out around the edge of the atom.
They orbit the nucleus in layers called shells .
In an atom the number of positive protons is the same as the number of negative electrons.

Nucleus contains protons and neutrons, overall charge is positive.
Most of an atoms mass is found here.
Most of the atom is empty space.
Electrons give the atom it’s overall size and shape.
An atom has no overall charge because the number of positive protons is the same as the number of negative electrons.

An actual AS chemistry exam question
White boards

The number of protons is what determines which element it is.
8 protons = oxygen
2 protons = helium
But the number of neutrons can vary.
If the neutrons vary then what else will vary?
If neutrons vary then so does the atoms….
….mass!

Definition:
• Isotopes are atoms of the same element with different numbers of neutrons.
• Isotopes of an element will have:
– different masses
– the same number of protons and electrons
– different numbers of neutrons
• Isotopes of an element react in exactly the same way because reactions involve electrons, neutrons have no effect on chemical reactions.

Mass number (nucleon number) total number of protons and neutrons in the nucleus
Element symbol
A
Z
X
Symbol for an isotope
Atomic (proton) number
1) Number of protons in the nucleus – defines the element
2)All atoms of the same element have the same number of protons

Chlorine -35 and -37 are examples of isotopes
Different mass numbers mean different numbers of neutrons
18 neutrons
(35 – 17)
35
17
Cl
17
37 Cl
20 neutrons
(37 – 17)
The atomic numbers are the same. Both isotopes have 17 electrons and 17 protons
Remember
Number of neutrons = mass number – atomic number

Carbon is a mixture of three isotopes, for each of them complete the table:
13
6
14
6
Isotope
Mass number
Atomic Number
No. of neutrons
White boards
12
6

Actual year 12 exam question
White boards

What is an ion?
It is an atom that is charged.
How does this happen?
Either by gaining or losing one or more electrons.
Definition
An ion is a positively or negatively charged atom or (covalently bonded) group of atoms
(a molecular ion)

• Ions have different numbers of protons and electrons

White boards
Complete the table:
Ion
23
11
+ 35
17
-
Mass number, A
Atomic Number, Z
No. of protons
No. of neutrons
No. of electrons
Overall charge

White boards

Complete on worksheet
Q 1

More Exam Questions
We will look at more exam questions for this topic.
This is work that we have covered at GCSE, but it is important that we understand these topics as they are fundamental ideas in chemistry and you will constantly come back to them.
Also it is good to look at exam papers. Some questions will look similar, that is because they are!
This means you can easily pick up marks or lose
marks if you constantly make the same mistakes.
Look at past exam papers and mark schemes. Use them to help with your revision. See what the key words are that the exam board are looking for and see what the key things are that they are not looking for.
Just like with GCSE they are freely available on the internet.

Complete the following exam questions on the worksheet
Q 2

Q 2

Q 2 ii

Q 3

Q 3

Q 3

Q 4

Q 5

Q 6

Ionic formula

a) How many protons, neutrons and electrons are in the following atoms and ions?
b) Which are atoms and ions? How do you know?
1) 17
3
Li 2) 24
11
Na 3) 19
9
F 4) 55
26
Fe
5) 39
19
K + 6) 19
9
F 7) 39
20
Ca 2+ 8) 17
8
O 2-

1. Hydrogen, deuterium and tritium are all isotopes of each other. a) Identify one similarity and one difference between these isotopes.
b) Deuterium can be written as 2 H. Determine the number of protons, neutrons and electrons in a neutral deuterium atom.
c) Write a nuclear symbol for tritium, given that it has 2 neutrons.
2. A certain atom X has one less proton and two more neutrons than K. What are its atomic number and mass number?
3. Explain in terms of sub atom particles, why C-12 and C-14 are isotopes

Atomic Structure
• (a) describe protons, neutrons and electrons in terms of relative charge and relative mass;
• (b) describe the distribution of mass and charge within an atom;
• (c) describe the contribution of protons and neutrons to the nucleus of an atom, in terms of atomic (proton) number and mass (nucleon) number;
• (d) deduce the numbers of protons, neutrons and electrons in:
– (i) an atom given its atomic and mass number,
– (ii) an ion given its atomic number, mass number and ionic charge;
• (e) explain the term isotopes as atoms of an element with different numbers of neutrons and different masses;