Inorganic Chemistry

Introduction to Chemistry - Definition of Chemistry
Introduction to Chemistry - Branches of Chemistry

By the end of the lesson, the learner should be able to:

- Explain the meaning of Chemistry as a field of science
- Discuss the branches of Chemistry
- Connect Chemistry to everyday products like soap, medicine and plastics

- Identify the main branches of Chemistry
- Classify substances according to branches of Chemistry
- Link Chemistry branches to career opportunities in medicine, agriculture and manufacturing

- Discuss with peers the meaning of Chemistry as a field of science
- Discuss with peers the branches of Chemistry
- Categorise daily items into branches of Chemistry

- Search for information using electronic and/or print media on branches of Chemistry
- Match everyday items with related branches of Chemistry
- Present findings to class members

What is Chemistry and why do we study it?
How do the different branches of Chemistry relate to items we use daily?

- Front Row Chemistry Grade 10 pg. 1
- Digital devices
- Samples of everyday products

- Front Row Chemistry Grade 10 pg. 2
- Digital devices
- Product samples with labels

- Oral questions - Observation - Written exercises
- Observation - Written exercises - Peer assessment

Inorganic Chemistry

Introduction to Chemistry - Chemistry in daily life (Manufacturing and Materials)

By the end of the lesson, the learner should be able to:

- Explain the role of Chemistry in manufacturing industry
- Discuss Chemistry applications in advanced materials development
- Relate Chemistry to the production of items like plastics, fuels and cosmetics

- Brainstorm the importance of Chemistry in manufacturing
- Examine products and identify chemical components
- Discuss applications of Chemistry in materials development

How does Chemistry contribute to the products we use every day?

- Front Row Chemistry Grade 10 pg. 3
- Samples of manufactured products
- Digital devices

- Oral questions - Group discussions - Written exercises

Inorganic Chemistry

Introduction to Chemistry - Chemistry in daily life (Food, Energy and Biotechnology)

By the end of the lesson, the learner should be able to:

- Describe the role of Chemistry in food industry and renewable energy
- Explain applications of Chemistry in biotechnology and agriculture
- Connect Chemistry to food preservation, solar cells and crop improvement

- Discuss Chemistry applications in food industry
- Search for information on renewable energy and biotechnology
- Share findings with classmates for discussion

How does Chemistry help in food production and energy generation?

- Front Row Chemistry Grade 10 pg. 3
- Food product labels
- Digital devices

- Written exercises - Observation - Oral questions

Inorganic Chemistry

Introduction to Chemistry - Careers in Chemistry

By the end of the lesson, the learner should be able to:

- Identify career opportunities related to Chemistry
- Analyse how gender stereotyping influences career choices
- Envision future career paths in fields like pharmacy, medicine and engineering

- Search for information on career opportunities related to Chemistry
- Discuss how gender stereotypes influence career choices
- Suggest ways to reduce gender stereotypes in careers

What careers can one pursue after studying Chemistry?

- Front Row Chemistry Grade 10 pg. 4
- Digital devices
- Career information materials

- Oral questions - Written assignments - Group presentations

Inorganic Chemistry

Introduction to Chemistry - Drug prescription and dosage
Introduction to Chemistry - Effects of drug and substance use

By the end of the lesson, the learner should be able to:

- Define the terms drug, prescription and dosage
- Differentiate between proper drug use and substance abuse
- Recognise the importance of following medical prescriptions for personal health

- Examine the effects of drug and substance use in day-to-day life
- Develop awareness materials on risks of substance abuse
- Make informed decisions about avoiding harmful substances

- Discuss with peers the meaning of drug, prescription and dosage
- Examine case studies on proper drug use
- Discuss consumer rights to drug information

- Brainstorm effects of drug and substance use
- Develop posters to sensitise peers on risks of substance abuse
- Present findings to class members

What is the difference between medicine and drug abuse?
What are the consequences of drug and substance abuse?

- Front Row Chemistry Grade 10 pg. 6
- Medicine packages with labels
- Digital devices

- Front Row Chemistry Grade 10 pg. 6
- Manila paper and markers
- Digital devices

- Oral questions - Written exercises - Observation
- Project work - Peer assessment - Observation

Inorganic Chemistry

Introduction to Chemistry - Laboratory safety and consumer protection

By the end of the lesson, the learner should be able to:

- Identify rights and responsibilities in a learning environment
- Demonstrate proper safety practices in the laboratory
- Apply safety rules to protect oneself and others during practical work

- Brainstorm on learner's rights and responsibilities to a safe learning environment
- Examine product certification marks and labels
- Create safety posters for display

How can we maintain a safe learning environment in the Chemistry laboratory?

- Front Row Chemistry Grade 10 pg. 10
- Safety equipment
- Product labels
- Manila paper

- Observation - Written exercises - Project work

Inorganic Chemistry

The Atom - Sub-atomic particles

By the end of the lesson, the learner should be able to:

- Describe the structure of the atom
- Identify the location and properties of protons, neutrons and electrons
- Relate atomic structure to understanding matter around us

- Review with peers the concept of the structure of the atom
- Discuss the properties of sub-atomic particles
- Model the structure of an atom using locally available materials

What particles make up an atom?

- Front Row Chemistry Grade 10 pg. 14
- Modelling materials
- Charts showing atomic structure

- Observation - Oral questions - Model assessment

Inorganic Chemistry

The Atom - Atomic number and mass number

By the end of the lesson, the learner should be able to:

- Define atomic number and mass number
- Calculate the number of protons, neutrons and electrons in atoms
- Use atomic notation to identify elements in everyday materials

- Discuss the relationship between atomic number, mass number and electrons
- Calculate sub-atomic particles for given elements
- Draw atomic structures using dots and crosses

How do we determine the number of particles in an atom?

- Front Row Chemistry Grade 10 pg. 15
- Periodic table
- Exercise books

- Written exercises - Oral questions - Individual assessment

Inorganic Chemistry

The Atom - Dalton's and Rutherford's atomic models
The Atom - Bohr's atomic model and Rutherford Gold Foil experiment

By the end of the lesson, the learner should be able to:

- Describe Dalton's and Rutherford's atomic models
- Compare different atomic models
- Value the contributions of scientists in advancing our understanding of matter

- Explain Bohr's planetary model of the atom
- Analyse the Rutherford Gold Foil experiment
- Connect scientific discoveries to modern technology like medical imaging

- Search for information on historical development of atomic models
- Draw diagrams of Dalton's and Rutherford's models
- Discuss limitations of each model

- Watch simulation on Rutherford Gold Foil experiment
- Discuss Bohr's contributions to atomic theory
- Compare models and identify improvements

How did scientists discover the structure of the atom?
What did the Rutherford Gold Foil experiment reveal about atomic structure?

- Front Row Chemistry Grade 10 pg. 16
- Printed diagrams of atomic models
- Digital devices

- Front Row Chemistry Grade 10 pg. 17
- Digital devices with internet
- Simulation videos

- Written exercises - Observation - Peer assessment
- Oral questions - Written exercises - Observation

Inorganic Chemistry

The Atom - Definition and examples of isotopes

By the end of the lesson, the learner should be able to:

- Define the term isotopes
- Identify isotopes of common elements
- Relate isotopes to applications in medicine and carbon dating

- Brainstorm the meaning of isotopes
- Examine isotopes of carbon and hydrogen
- Discuss similarities and differences between isotopes

Why do some atoms of the same element have different masses?

- Front Row Chemistry Grade 10 pg. 17
- Periodic table
- Charts showing isotopes

- Oral questions - Written exercises - Individual assessment

Inorganic Chemistry

The Atom - Calculating relative atomic mass

By the end of the lesson, the learner should be able to:

- Define relative atomic mass
- Calculate the relative atomic mass of elements from isotopic abundances
- Apply RAM calculations to understand element composition in fertilisers and medicines

- Discuss the meaning of relative atomic mass
- Calculate RAM using percentage abundances
- Solve practice problems on RAM

How do we calculate the average mass of atoms with different isotopes?

- Front Row Chemistry Grade 10 pg. 18
- Calculators
- Worked examples

- Written exercises - Individual assessment - Oral questions

Inorganic Chemistry

The Atom - Practice on relative atomic mass calculations

By the end of the lesson, the learner should be able to:

- Apply the formula for calculating relative atomic mass
- Solve problems involving unknown isotopic abundances
- Use RAM values to predict element behaviour in chemical reactions

- Practice calculating RAM for various elements
- Solve problems involving unknown variables
- Share solutions with peers for review

How can we determine isotopic abundance from relative atomic mass?

- Front Row Chemistry Grade 10 pg. 19
- Calculators
- Practice worksheets

- Written exercises - Peer assessment - Individual assessment

Inorganic Chemistry

The Atom - Relationship between energy levels and orbitals
The Atom - Order of filling electrons in orbitals

By the end of the lesson, the learner should be able to:

- Explain the relationship between energy levels and orbitals
- Identify s and p orbitals in atoms
- Connect electron arrangement to element properties like conductivity

- Describe the order of filling electrons in orbitals
- Apply the Aufbau principle in writing electron configurations
- Predict element reactivity based on electron arrangement

- Discuss energy levels and sub-shells
- Draw diagrams showing energy levels and orbitals
- Discuss electron capacity of different orbitals

- Carry out activities to illustrate order of filling orbitals
- Practice filling electrons in order
- Discuss with peers the filling sequence

How are electrons organised around the nucleus?
Why do electrons fill orbitals in a specific order?

- Front Row Chemistry Grade 10 pg. 20
- Diagrams of orbitals
- Coloured pencils

- Front Row Chemistry Grade 10 pg. 21
- Energy level diagrams
- Exercise books

- Oral questions - Written exercises - Observation
- Written exercises - Oral questions - Observation

Inorganic Chemistry

The Atom - Writing electron configuration (Elements 1-10)

By the end of the lesson, the learner should be able to:

- Write electron arrangement using s and p notation
- Apply notation to elements 1-10
- Use electron configuration to explain why neon is used in lighting

- Draw electron arrangements for elements 1-10 using s and p notation
- Practice writing configurations
- Compare configurations with peers

How do we represent electron arrangement using s and p notation?

- Front Row Chemistry Grade 10 pg. 22
- Periodic table
- Exercise books

- Written exercises - Individual assessment - Peer assessment

Inorganic Chemistry

The Atom - Writing electron configuration (Elements 1-10)

By the end of the lesson, the learner should be able to:

- Write electron arrangement using s and p notation
- Apply notation to elements 1-10
- Use electron configuration to explain why neon is used in lighting

- Draw electron arrangements for elements 1-10 using s and p notation
- Practice writing configurations
- Compare configurations with peers

How do we represent electron arrangement using s and p notation?

- Front Row Chemistry Grade 10 pg. 22
- Periodic table
- Exercise books

- Written exercises - Individual assessment - Peer assessment

Inorganic Chemistry

The Atom - Writing electron configuration (Elements 11-20)

By the end of the lesson, the learner should be able to:

- Write electron arrangement for elements 11-20 using s and p notation
- Identify patterns in electron configurations
- Connect electron arrangement to element uses in batteries and construction

- Draw electron arrangements for elements 11-20
- Identify patterns across periods
- Share work with classmates for review

How does electron configuration change across periods?

- Front Row Chemistry Grade 10 pg. 22
- Periodic table
- Exercise books

- Written exercises - Oral questions - Individual assessment

Inorganic Chemistry

The Atom - Modelling atomic structure

By the end of the lesson, the learner should be able to:

- Create models of atomic structure
- Demonstrate understanding of sub-atomic particle arrangement
- Connect atomic structure to properties of materials like metals and non-metals

- Select elements and create atomic models
- Display models to classmates for peer review
- Share experiences of making atomic models

How can we represent atomic structure using models?

- Front Row Chemistry Grade 10 pg. 23
- Locally available materials
- Modelling clay

- Project work - Peer assessment - Observation

Inorganic Chemistry

The Atom - Modelling atomic structure

By the end of the lesson, the learner should be able to:

- Create models of atomic structure
- Demonstrate understanding of sub-atomic particle arrangement
- Connect atomic structure to properties of materials like metals and non-metals

- Select elements and create atomic models
- Display models to classmates for peer review
- Share experiences of making atomic models

How can we represent atomic structure using models?

- Front Row Chemistry Grade 10 pg. 23
- Locally available materials
- Modelling clay

- Project work - Peer assessment - Observation

Inorganic Chemistry

The Periodic Table - Historical development

By the end of the lesson, the learner should be able to:

- Describe the historical development of the periodic table
- Identify contributions of Mendeleev and Moseley
- Value scientific collaboration that led to the modern periodic table

- Brainstorm on historical development of the periodic table
- Search for information on contributions of scientists
- Discuss evolution of the periodic table

How did scientists organise elements into the periodic table?

- Front Row Chemistry Grade 10 pg. 24
- Digital devices
- Printed periodic tables

- Oral questions - Written exercises - Group discussions

Inorganic Chemistry

The Periodic Table - Arrangement into groups and periods

By the end of the lesson, the learner should be able to:

- Arrange elements into groups and periods
- Relate electron arrangement to position in periodic table
- Use the periodic table to identify elements in common materials

- Arrange the first 20 elements into groups and periods
- Discuss relationship between electron configuration and position
- Complete periodic table activities

Why are elements arranged in groups and periods?

- Front Row Chemistry Grade 10 pg. 26
- Periodic table charts
- Exercise books

- Written exercises - Observation - Oral questions

Inorganic Chemistry

The Periodic Table - Alkali metals and alkaline earth metals
The Periodic Table - Halogens and noble gases

By the end of the lesson, the learner should be able to:

- Identify chemical families in the periodic table
- Describe properties of alkali metals and alkaline earth metals
- Connect chemical families to uses like sodium in street lights and calcium in bones

- Describe properties of halogens and noble gases
- Compare different chemical families
- Relate noble gas stability to their use in light bulbs and balloons

- Identify chemical families of elements
- Discuss characteristics of Group I and II elements
- List elements in each chemical family

- Discuss characteristics of Group VII and VIII elements
- Compare properties of different chemical families
- Present findings to classmates

What are chemical families and why are they important?
Why are noble gases called inert gases?

- Front Row Chemistry Grade 10 pg. 28
- Periodic table
- Charts showing chemical families

- Front Row Chemistry Grade 10 pg. 28
- Periodic table
- Digital devices

- Oral questions - Written exercises - Group discussions
- Written exercises - Oral questions - Observation

Inorganic Chemistry

The Periodic Table - Duplet and octet rule

By the end of the lesson, the learner should be able to:

- Explain the stability of atoms
- Apply duplet and octet rules
- Understand why elements react to become stable like salt formation

- Discuss with peers the stability of atoms
- Examine electron configurations of stable atoms
- Identify elements that follow duplet or octet rule

Why are some atoms stable while others are reactive?

- Front Row Chemistry Grade 10 pg. 29
- Periodic table
- Diagrams of stable configurations

- Oral questions - Written exercises - Observation

Inorganic Chemistry

The Periodic Table - Formation of cations

By the end of the lesson, the learner should be able to:

- Predict the type of ion formed from electron arrangement
- Draw ionic structures of cations
- Connect cation formation to properties of metals like conductivity

- Discuss how metallic atoms lose electrons
- Draw ionic structures of cations
- Write ionic equations for cation formation

How do metal atoms form positive ions?

- Front Row Chemistry Grade 10 pg. 30
- Exercise books
- Diagrams showing ion formation

- Written exercises - Individual assessment - Oral questions

Inorganic Chemistry

The Periodic Table - Formation of anions

By the end of the lesson, the learner should be able to:

- Explain how non-metallic atoms form anions
- Draw ionic structures of anions
- Relate anion formation to salt production in food industry

- Discuss how non-metallic atoms gain electrons
- Draw ionic structures of anions
- Compare cation and anion formation

How do non-metal atoms form negative ions?

- Front Row Chemistry Grade 10 pg. 31
- Exercise books
- Diagrams showing anion formation

- Written exercises - Peer assessment - Oral questions

Inorganic Chemistry

The Periodic Table - Writing electron configuration of ions using s and p notation
The Periodic Table - Valency of elements

By the end of the lesson, the learner should be able to:

- Write electron arrangement of ions using s and p notation
- Compare electron configurations of atoms and ions
- Apply ionic configurations to understand compound formation

- Define valency and determine valency from group number
- Identify valencies of common elements
- Use valency to predict how elements combine in fertilisers and medicines

- Write electron configurations for various ions
- Compare configurations of atoms and their ions
- Practice with different elements

- Discuss the relationship between valency and oxidation number
- Infer valency from electron arrangement
- Complete tables showing valencies

How does electron configuration change when ions form?
What is valency and how is it determined?

- Front Row Chemistry Grade 10 pg. 32
- Periodic table
- Exercise books

- Front Row Chemistry Grade 10 pg. 33
- Periodic table
- Valency charts

- Written exercises - Individual assessment - Observation
- Oral questions - Written exercises - Individual assessment

Inorganic Chemistry

The Periodic Table - Elements with variable oxidation numbers

By the end of the lesson, the learner should be able to:

- Identify elements with variable oxidation numbers
- Explain why some elements show variable valency
- Connect variable valency to rust formation (iron) and paint pigments (lead)

- Discuss elements with variable oxidation numbers
- Examine examples like iron, copper and lead
- Practice identifying oxidation states

Why do some elements have more than one oxidation number?

- Front Row Chemistry Grade 10 pg. 34
- Periodic table
- Examples of compounds

- Written exercises - Oral questions - Observation

Inorganic Chemistry

The Periodic Table - Elements with variable oxidation numbers

By the end of the lesson, the learner should be able to:

- Identify elements with variable oxidation numbers
- Explain why some elements show variable valency
- Connect variable valency to rust formation (iron) and paint pigments (lead)

- Discuss elements with variable oxidation numbers
- Examine examples like iron, copper and lead
- Practice identifying oxidation states

Why do some elements have more than one oxidation number?

- Front Row Chemistry Grade 10 pg. 34
- Periodic table
- Examples of compounds

- Written exercises - Oral questions - Observation

Inorganic Chemistry

The Periodic Table - Common radicals and their valencies

By the end of the lesson, the learner should be able to:

- Define radicals and identify common radicals
- State valencies of common radicals
- Apply knowledge of radicals to understand compound names in cleaning products

- List examples of radicals and their valencies
- Discuss characteristics of radicals
- Practice identifying radicals in compounds

What are radicals and how do they combine with other elements?

- Front Row Chemistry Grade 10 pg. 35
- Charts showing radicals
- Exercise books

- Written exercises - Oral questions - Individual assessment

Inorganic Chemistry

The Periodic Table - Deriving formulae using valencies

By the end of the lesson, the learner should be able to:

- Derive chemical formulae using valencies
- Apply the cross-over method
- Write correct formulae for compounds used in daily life like baking soda and salt

- Practice writing formulae using valencies and oxidation states
- Apply cross-over method to derive formulae
- Verify formulae with peers

How do we write chemical formulae using valencies?

- Front Row Chemistry Grade 10 pg. 36
- Valency charts
- Exercise books

- Written exercises - Individual assessment - Peer assessment

Inorganic Chemistry

The Periodic Table - Deriving formulae using valencies

By the end of the lesson, the learner should be able to:

- Derive chemical formulae using valencies
- Apply the cross-over method
- Write correct formulae for compounds used in daily life like baking soda and salt

- Practice writing formulae using valencies and oxidation states
- Apply cross-over method to derive formulae
- Verify formulae with peers

How do we write chemical formulae using valencies?

- Front Row Chemistry Grade 10 pg. 36
- Valency charts
- Exercise books

- Written exercises - Individual assessment - Peer assessment

Inorganic Chemistry

The Periodic Table - Formulae of compounds with same valency

By the end of the lesson, the learner should be able to:

- Write formulae for compounds with elements of same valency
- Simplify chemical formulae appropriately
- Apply formula writing to common compounds like table salt (NaCl)

- Practice writing formulae for compounds with same valencies
- Simplify formulae to lowest terms
- Complete exercises on formula writing

How do we simplify chemical formulae?

- Front Row Chemistry Grade 10 pg. 37
- Exercise books
- Worked examples

- Written exercises - Oral questions - Individual assessment

Inorganic Chemistry

The Periodic Table - Formulae of compounds with same valency

By the end of the lesson, the learner should be able to:

- Write formulae for compounds with elements of same valency
- Simplify chemical formulae appropriately
- Apply formula writing to common compounds like table salt (NaCl)

- Practice writing formulae for compounds with same valencies
- Simplify formulae to lowest terms
- Complete exercises on formula writing

How do we simplify chemical formulae?

- Front Row Chemistry Grade 10 pg. 37
- Exercise books
- Worked examples

- Written exercises - Oral questions - Individual assessment

Inorganic Chemistry

The Periodic Table - Formulae of compounds with different valencies

By the end of the lesson, the learner should be able to:

- Write formulae for compounds with different valencies
- Apply the cross-over method correctly
- Derive formulae for compounds like carbon dioxide and sulphuric acid

- Practice writing formulae for compounds with different valencies
- Apply cross-over method systematically
- Share solutions with classmates

How do we write formulae when elements have different valencies?

- Front Row Chemistry Grade 10 pg. 37
- Exercise books
- Practice worksheets

- Written exercises - Peer assessment - Individual assessment

Inorganic Chemistry

The Periodic Table - Formulae of compounds containing radicals

By the end of the lesson, the learner should be able to:

- Write formulae for compounds containing radicals
- Apply brackets correctly for polyatomic ions
- Write formulae for fertilisers like ammonium sulphate and calcium phosphate

- Practice writing formulae with radicals
- Use brackets for polyatomic ions when necessary
- Complete exercises on compounds with radicals

How do we write formulae for compounds with radicals?

- Front Row Chemistry Grade 10 pg. 38
- Radical valency charts
- Exercise books

- Written exercises - Individual assessment - Oral questions

Inorganic Chemistry

The Periodic Table - Formulae of compounds containing radicals

By the end of the lesson, the learner should be able to:

- Write formulae for compounds containing radicals
- Apply brackets correctly for polyatomic ions
- Write formulae for fertilisers like ammonium sulphate and calcium phosphate

- Practice writing formulae with radicals
- Use brackets for polyatomic ions when necessary
- Complete exercises on compounds with radicals

How do we write formulae for compounds with radicals?

- Front Row Chemistry Grade 10 pg. 38
- Radical valency charts
- Exercise books

- Written exercises - Individual assessment - Oral questions

Inorganic Chemistry

The Periodic Table - Writing word equations

By the end of the lesson, the learner should be able to:

- Represent chemical reactions using word equations
- Identify reactants and products
- Describe reactions occurring in cooking and cleaning

- Write word equations for simple chemical reactions
- Identify reactants and products in reactions
- Practice converting descriptions to word equations

How do we represent chemical reactions using words?

- Front Row Chemistry Grade 10 pg. 39
- Exercise books
- Reaction examples

- Written exercises - Oral questions - Observation

Inorganic Chemistry

The Periodic Table - Writing symbol equations

By the end of the lesson, the learner should be able to:

- Convert word equations to symbol equations
- Write correct chemical formulae in equations
- Represent reactions like burning magnesium and rusting of iron

- Convert word equations to symbol equations
- Apply correct formulae in equations
- Practice writing symbol equations

How do we write chemical equations using symbols?

- Front Row Chemistry Grade 10 pg. 39
- Exercise books
- Formula charts

- Written exercises - Individual assessment - Peer assessment

Inorganic Chemistry

The Periodic Table - Writing symbol equations

By the end of the lesson, the learner should be able to:

- Convert word equations to symbol equations
- Write correct chemical formulae in equations
- Represent reactions like burning magnesium and rusting of iron

- Convert word equations to symbol equations
- Apply correct formulae in equations
- Practice writing symbol equations

How do we write chemical equations using symbols?

- Front Row Chemistry Grade 10 pg. 39
- Exercise books
- Formula charts

- Written exercises - Individual assessment - Peer assessment

Inorganic Chemistry

The Periodic Table - Balancing chemical equations

By the end of the lesson, the learner should be able to:

- Balance chemical equations using appropriate coefficients
- Apply the law of conservation of mass
- Relate balanced equations to industrial processes like fertiliser production

- Write balanced chemical equations for simple reactions
- Practice balancing various equations
- Share solutions with classmates for review

Why must chemical equations be balanced?

- Front Row Chemistry Grade 10 pg. 40
- Exercise books
- Practice worksheets

- Written exercises - Individual assessment - Oral questions

Inorganic Chemistry

The Periodic Table - Balancing chemical equations

By the end of the lesson, the learner should be able to:

- Balance chemical equations using appropriate coefficients
- Apply the law of conservation of mass
- Relate balanced equations to industrial processes like fertiliser production

- Write balanced chemical equations for simple reactions
- Practice balancing various equations
- Share solutions with classmates for review

Why must chemical equations be balanced?

- Front Row Chemistry Grade 10 pg. 40
- Exercise books
- Practice worksheets

- Written exercises - Individual assessment - Oral questions