7.1.7
Atoms & Ions
After reading these notes, test your knowledge with free interactive questions on Seneca — used by over 10 million students.
Atoms and Ions
Atoms have no overall electrical charge. When an atom becomes charged by gaining or losing electrons it becomes an ion.

Atoms are neutral
- In an atom, the number of electrons is equal to the number of protons in the nucleus.
- Atoms have no overall electrical charge.
Positive ions
- Atoms turn into positive ions if they lose one or more outer electrons.
Negative ions
- Atoms turn into negative ions if they gain one or more electrons.
1Forces & Motion
1.1Basics of Motion
1.1.1Average Speed1.1.2Acceleration1.1.3Distance & Displacement1.1.4Velocity1.1.5Adding Vectors1.1.6Distance-Time Graphs1.1.7Speed-Time Graphs 11.1.8Speed-Time Graphs 21.1.9Initial & Final Speed, Acceleration, Distance1.1.10Average Speed - Calculations1.1.11Acceleration - Calculations1.1.12Uniform Acceleration - Calculations1.1.13Grade 9 - Motion1.1.14Exam-Style Questions - Graphs of Motion
1.2Forces
1.3Effects of Forces
1.3.1Momentum - No Impulse1.3.2Momentum1.3.3Momentum: Law of Conservation1.3.4Force & Momentum Change1.3.5Momentum - Safety1.3.6Change in Momentum - Calculations1.3.7Momentum - Calculations1.3.8Mass1.3.9Weight1.3.10Centre of Mass1.3.11Gravity - Calculations1.3.12Free Fall1.3.13Air Resistance & Friction1.3.14Graphs of Motion with Air Resistance1.3.15Turning Effect1.3.16Moments1.3.17Equilibrium1.3.18Moments - Calculations1.3.19Exam-Style Questions - Moments
1.4Stopping Distance
1.5Forces & Elasticity
1.5.1Stretching, Bending & Compressing1.5.2Elastic Deformation vs Inelastic Deformation1.5.3Hooke's Law1.5.4Hooke's Law - Equation1.5.5Hooke's Law - Spring Experiments1.5.6Hooke's Law - Calculations1.5.7Elastic Potential - Calculations1.5.8End of Topic Test - Forces1.5.9Exam-Style Questions - Elastic Potential
2Electricity
2.1Electricity in Homes
2.2Current & Potential Difference
2.3Resistance & Power
2.4Electric Circuits
2.4.1Circuit Diagrams2.4.2Circuit Symbols2.4.3Diodes2.4.4LDRs & Thermistors2.4.5Series Circuits2.4.6Resistors in Series2.4.7Series Circuits - Calculations2.4.8Parallel Circuits2.4.9Parallel Circuits in Practice2.4.10End of Topic Test - Electricity2.4.11Grade 9 - Circuits2.4.12Exam-Style Questions - Electrical Circuits
3Waves
3.1Wave Basics
3.2Waves at a Boundary
3.3Electromagnetic Spectrum
3.4Sound Waves
3.5Communications
4Energy Resources & Energy Transfers
4.1Energy Changes
4.1.1Energy Stores4.1.2Conservation of Energy4.1.3Examples of Energy Conversion4.1.4Kinetic Energy Stored4.1.5Gravitational Potential Energy Stored4.1.6Elastic Potential Energy Stored4.1.7Changes in Kinetic Energy - Calculations4.1.8Changes in GPE - Calculations4.1.9Changes in EPE - Calculations4.1.10Mechanical Work Done4.1.11Mechanical Work Done - Equation4.1.12Power4.1.13Mechanical Work - Calculations4.1.14Electrical Work Done- Calculations
4.2Energy Losses & Efficiency
4.3Energy Resources
5Solids, Liquids & Gases
5.1Density & Pressure
5.2Changing State
6Magnetism & Electromagnetism
6.1Magnetism
6.2Electromagnetism
6.3Electromagnetic Induction
6.4Transformers
6.4.1Transformers6.4.2Transformer Equation6.4.3Step-Up & Step-Down Transformers6.4.4Principles of Transformer Operation6.4.5High-Voltage Transmission & Transformers6.4.6Transformers - Calculations6.4.7Transformers 2 - Calculations6.4.8Energy in Transformers6.4.9Power Losses in Cables6.4.10End of Topic Test - Magnetism6.4.11Grade 9 - Transformers6.4.12Exam-Style Questions - Transformers
7Radioactivity & Particles
7.1Atoms
7.2Radioactivity
7.2.1Radioactive Decay7.2.2Types of Radiation7.2.3Three Types of Emission7.2.4Ionising vs Penetration7.2.5Nuclear Fission7.2.6Nuclear Reactors7.2.7Nuclear Fission - Uncontrolled Chain Reaction7.2.8Radioactive Decay7.2.9Decay Equations7.2.10Nuclear Fission Equation7.2.11Half Life & Background Radiation7.2.12Measuring Half-Life From a Graph7.2.13Background Radiation7.2.14Practical Applications of Radiation7.2.15Ions & Ionising Radiation7.2.16Safety Precautions7.2.17Peer Review7.2.18End of Topic Test - Radioactivity & Particles7.2.19Grade 9 - Radioactivity & Particles7.2.20Exam-Style Questions - Radioactive Decay
8Astrophysics
8.1Motion in the Universe
8.2Evolution of Stars
Jump to other topics
1Forces & Motion
1.1Basics of Motion
1.1.1Average Speed1.1.2Acceleration1.1.3Distance & Displacement1.1.4Velocity1.1.5Adding Vectors1.1.6Distance-Time Graphs1.1.7Speed-Time Graphs 11.1.8Speed-Time Graphs 21.1.9Initial & Final Speed, Acceleration, Distance1.1.10Average Speed - Calculations1.1.11Acceleration - Calculations1.1.12Uniform Acceleration - Calculations1.1.13Grade 9 - Motion1.1.14Exam-Style Questions - Graphs of Motion
1.2Forces
1.3Effects of Forces
1.3.1Momentum - No Impulse1.3.2Momentum1.3.3Momentum: Law of Conservation1.3.4Force & Momentum Change1.3.5Momentum - Safety1.3.6Change in Momentum - Calculations1.3.7Momentum - Calculations1.3.8Mass1.3.9Weight1.3.10Centre of Mass1.3.11Gravity - Calculations1.3.12Free Fall1.3.13Air Resistance & Friction1.3.14Graphs of Motion with Air Resistance1.3.15Turning Effect1.3.16Moments1.3.17Equilibrium1.3.18Moments - Calculations1.3.19Exam-Style Questions - Moments
1.4Stopping Distance
1.5Forces & Elasticity
1.5.1Stretching, Bending & Compressing1.5.2Elastic Deformation vs Inelastic Deformation1.5.3Hooke's Law1.5.4Hooke's Law - Equation1.5.5Hooke's Law - Spring Experiments1.5.6Hooke's Law - Calculations1.5.7Elastic Potential - Calculations1.5.8End of Topic Test - Forces1.5.9Exam-Style Questions - Elastic Potential
2Electricity
2.1Electricity in Homes
2.2Current & Potential Difference
2.3Resistance & Power
2.4Electric Circuits
2.4.1Circuit Diagrams2.4.2Circuit Symbols2.4.3Diodes2.4.4LDRs & Thermistors2.4.5Series Circuits2.4.6Resistors in Series2.4.7Series Circuits - Calculations2.4.8Parallel Circuits2.4.9Parallel Circuits in Practice2.4.10End of Topic Test - Electricity2.4.11Grade 9 - Circuits2.4.12Exam-Style Questions - Electrical Circuits
3Waves
3.1Wave Basics
3.2Waves at a Boundary
3.3Electromagnetic Spectrum
3.4Sound Waves
3.5Communications
4Energy Resources & Energy Transfers
4.1Energy Changes
4.1.1Energy Stores4.1.2Conservation of Energy4.1.3Examples of Energy Conversion4.1.4Kinetic Energy Stored4.1.5Gravitational Potential Energy Stored4.1.6Elastic Potential Energy Stored4.1.7Changes in Kinetic Energy - Calculations4.1.8Changes in GPE - Calculations4.1.9Changes in EPE - Calculations4.1.10Mechanical Work Done4.1.11Mechanical Work Done - Equation4.1.12Power4.1.13Mechanical Work - Calculations4.1.14Electrical Work Done- Calculations
4.2Energy Losses & Efficiency
4.3Energy Resources
5Solids, Liquids & Gases
5.1Density & Pressure
5.2Changing State
6Magnetism & Electromagnetism
6.1Magnetism
6.2Electromagnetism
6.3Electromagnetic Induction
6.4Transformers
6.4.1Transformers6.4.2Transformer Equation6.4.3Step-Up & Step-Down Transformers6.4.4Principles of Transformer Operation6.4.5High-Voltage Transmission & Transformers6.4.6Transformers - Calculations6.4.7Transformers 2 - Calculations6.4.8Energy in Transformers6.4.9Power Losses in Cables6.4.10End of Topic Test - Magnetism6.4.11Grade 9 - Transformers6.4.12Exam-Style Questions - Transformers
7Radioactivity & Particles
7.1Atoms
7.2Radioactivity
7.2.1Radioactive Decay7.2.2Types of Radiation7.2.3Three Types of Emission7.2.4Ionising vs Penetration7.2.5Nuclear Fission7.2.6Nuclear Reactors7.2.7Nuclear Fission - Uncontrolled Chain Reaction7.2.8Radioactive Decay7.2.9Decay Equations7.2.10Nuclear Fission Equation7.2.11Half Life & Background Radiation7.2.12Measuring Half-Life From a Graph7.2.13Background Radiation7.2.14Practical Applications of Radiation7.2.15Ions & Ionising Radiation7.2.16Safety Precautions7.2.17Peer Review7.2.18End of Topic Test - Radioactivity & Particles7.2.19Grade 9 - Radioactivity & Particles7.2.20Exam-Style Questions - Radioactive Decay
8Astrophysics
8.1Motion in the Universe
8.2Evolution of Stars
Practice questions on Atoms & Ions
Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.
- 1
- 2How does the loss of electrons affect the charge of an atom?Multiple choice
- 3
- 4
- 5
Unlock your full potential with Seneca Premium
Unlimited access to 10,000+ open-ended exam questions
Mini-mock exams based on your study history
Unlock 800+ premium courses & e-books