1. Atomic Structure Learning Objectives: Do I know.. The structure of an atom? About the relative size of the nucleus? That atoms of a given element have the same number of protons in the nucleus? The meaning of the terms ‘atomic number’ and ‘mass number’?

2. Starter Think, Pair and Share… True or False…? ◦ Atoms cannot be split up into anything smaller. ◦ Atoms are solid objects and nothing can pass through them. ◦ There are millions of different kinds of atoms. ◦ No-one has ever seen an atom.

3. Starter Think, Pair and Share… True or False…? ◦ Atoms cannot be split up into anything smaller. ◦ Atoms are solid objects and nothing can pass through them. ◦ There are millions of different kinds of atoms. ◦ No-one has ever seen an atom. False!

4. What is an atom made of? All matter is made up of particles called atoms. These atoms are made up of even simpler sub- atomic particles. These are called protons, electrons, and neutrons. Challenge Draw the diagram to the left. Can you add these labels? Nucleus Proton Neutron Electron shells Electron

5. What is an atom made of? At the centre of an atom is a positive nucleus. If the atom was the size of the O2 arena, the nucleus would be the size of a table tennis ball! The nucleus is made up of positive protons, and neutral neutrons. The nucleus is surrounded by electrons. These electrons are arranged in layers, or shells, sometimes these shells are called energy levels. Nucleus Proton Neutron Electron Electron Shells

6. What is an atom made of? Complete your table using the information about sub-atomic particles around the room. ParticleRelative ChargeRelative MassWhere in the atom is it found? Proton+ 11In the nucleus Neutron01In the nucleus Electron- 1Almost 0 (actually 0.0005) In shells surrounding the nucleus

7. Atomic number and mass number So far scientists have identified 118 different types of atom. This means there are 118 different elements. Each element has a fixed number of protons in its nucleus. Look at Lithium (Li) on your Periodic Table

8. Atomic number and mass number Lithium looks like this on the table, this is known as the ‘nuclear symbol.’ Li 7 3 We know that the ‘Li’ is the chemical symbol for lithium, but what do those numbers mean? This is the atomic number for lithium. This number tells us how many protons are in the nucleus. No other element has the same atomic number as lithium. This is the mass number. The mass number of an atom is the total number of protons and neutrons in the nucleus.

9. Atomic number and mass number The chemical symbol for Phosphorus (P) is shown below. How many protons and neutrons are in its nucleus? P 31 15

10. Atomic number and mass number The atomic number is 15. This is the number of protons in the nucleus. The mass number is 31. This is the total number of protons and neutrons in the nucleus. So, 31 – 15 = 16. P 31 15

11. Test Yourself 1. Using the chemical symbols shown for these atoms, write down the numbers of protons and neutrons in the nucleus of each atom. 2. An atom of potassium (K), has 19 protons and 20 neutrons in its nucleus. Write down the chemical symbol for this atom. O 16 8 Na 23 11

12. Test Yourself Swap your work with the person sitting next to you. 1. Oxygen (O) has 8 protons and 8 neutrons. Sodium (Na) has 11 protons, and 12 neutrons. 2. The nuclear symbol for potassium should look like this: K 39 19