Lesson focus: protonA tiny particle with a positive charge, found in the nucleus of an atom. number fixes elementA substance made of only one type of atom, such as oxygen or iron. identity; electronA tiny particle with a negative charge that moves around the outside of an atom. number fixes atomic charge.
Describe atomic structure and distinguish a neutral atomThe tiny particle that everything is made of; each element has its own kind of atom. from an ionAn atom (or group of atoms) that has an electric charge because it has gained or lost electrons..
Build on earlier learning
The particle modelRefine the general word particle into an atomic model with internal structure.
You will be successful when you can…
- Locate three subatomic particles.
- State relative charges and masses.
- Use proton number to identify an element.
- Calculate simple ion charge.
Words that carry the science
- atom
- Smallest particle of an element retaining its chemical identity.
- proton
- Nuclear particle with relative charge +1 and mass about 1.
- neutron
- Nuclear particle with charge 0 and mass about 1.
- electron
- Particle with charge −1 and very small relative mass.
- ion
- Charged particle formed when electrons are gained or lost.
Separate identity, mass and charge
01Most mass is in a tiny nucleus
protonA tiny particle with a positive charge, found in the nucleus of an atom. and neutronA tiny particle with no charge, found in the nucleus of an atom. occupy the nucleus; electronA tiny particle with a negative charge that moves around the outside of an atom. occupy surrounding regions. Diagrams greatly enlarge the nucleus and are not to scale.
02Protons define the element
Atomic/proton number is the number of protons. Most hydrogen atomThe tiny particle that everything is made of; each element has its own kind of atom. have one proton and no neutron, so “all nuclei contain neutrons” is false.
03Electrons change charge
Equal proton and electron numbers give neutrality. Losing electrons gives a positive ionAn atom (or group of atoms) that has an electric charge because it has gained or lost electrons.; gaining gives a negative ion.
Build an atom
The number of protons decides the element. Neutrons add mass but not charge; atoms of one element with different numbers of neutrons are isotopes. Electrons fill shells (2, then 8, then 8); if they do not match the protons, you have an ion.
Proton Neutron Electron
Controls
Find an ion charge
A particle has 12 protons and 10 electrons.
- Proton charge total = +12.
- Electron charge total = −10.
- Net charge = +12 − 10 = +2.
- It is a 2+ ion; 12 protons still define magnesium.
How to make the reasoning visible: Charge = proton number − electron number.
Atomic count table
Determine neutrality or charge.
| Protons | Neutrons | Electrons | Classification |
|---|---|---|---|
| 6 | 6 | 6 | Neutral carbon atom |
| 8 | 8 | 10 | Oxide ion, 2− |
| 11 | 12 | 10 | Sodium ion, 1+ |
| 1 | 0 | 1 | Common hydrogen atom |
Which count determines element identity?
Why is the hydrogen row important?
Use the table. Why is the neutral carbon atom neutral?
Check your understanding
Answer from memory, then check against the suggested answer.
What is atom?
What is proton?
What is neutron?
What charge does an electron have?
Where are protons and neutrons found?
A particle gains one electron. Does its element change?
Why is an atom mostly empty space yet matter feels solid?
An atom has 11 protons and 11 electrons. It loses one electron. What is its charge now?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
An atom has 9 protons, 10 neutrons and 9 electrons. It then gains one electron.
Explain why the atom has no overall charge before it gains the electron.
(1)Complete the sentence about the atom after it gains the electron.
(2)It now has electrons, so its overall charge is (positive, negative or neutral).
Explain whether the element changes.
(1)Total for this question: 4 marks
Command word: Show the charge calculation and identify the invariant proton number.