# Ions

pHun Reactions - 10SCIE

2021

## Akoranga 5 Mahi Tuatahi

• 10 min: Finish making or practise your flashcards
• 10 min: Complete the electron configuration worksheet

## Ngā Whāinga Ako

1. Can describe why ions form and identify the difference between cations & anions
2. Locate groups 1, 2, 16, 17, 18 elements on the periodic table and identify their number of valence electrons
3. Describe how ionic bonds are formed from the transfer of electrons

Write the date and ngā whāinga ako in your book

## Ions

An atom or molecule that has gained or lost electrons, and has become charged.

• Atoms are more stable when they have a full valence (outer) shell
• Atoms with an almost full valence shell will take electrons from other atoms
• Atoms with not many valence electrons will donate electrons to other atoms

### Tauria/Example: Sodium Fluoride

• Sodium only has one valence electron, and can donate it
• Fluorine is only one electron away from a full shell, so will take one
• Sodium becomes positively charged because it lost an electron
• Fluorine becomes negatively charged because it gained an electron
• They are attracted together and form sodium fluoride
• This is called an ionic bond - a bond between ions

### Tauria/Example: Sodium Chloride

• Sodium only has one valence electron, and can donate it
• Chlorine is only one electron away from a full shell, so will take one
• Sodium becomes positively charged because it lost an electron
• Chlorine becomes negatively charged because it gained an electron
• They are attracted together and form sodium chloride

### Which Atoms Form Ions?

• Only atoms in groups 1, 2, 16, and 17 ions
• Groups are vertical columns on the periodic table

Open your periodic table an find groups 1, 2, 16 and 17

Highlight these columns and add a label saying they will form ions.

1. Open to your ionic configuration diagrams
2. Look at the valence shell of groups 1, 2, 16, 17 and 18
3. Pātai: What do all the elements in each group have in common?
• Elements in group 1 have 1 valence electron
• Elements in group 2 have 2 valence electrons
• Elements in group 18 have a full valence shell
• Elements in group 17 are missing 1 electron
• Elements in group 16 are missing 2 electrons

### What is Special About Group 18?

• They have a full valence shell
• This means they do not want to take or give any electrons
• This means they are already very stable
• This means they do not react!

## Akoranga 7 Mahi Tuatahi

Work in pairs to answer these questions:

1. What is the formula of the hydrogen ion?
2. What is the formula of the oxide ion?
3. What is the formula of the iron (II) ion?
4. What is the name of the $$OH^{-}$$ ion?
5. What is the name of the $$Cl^{-}$$ ion?

## Ngā Whāinga Ako

1. Be able to define cation and anion
2. Be able to name ionic compounds

Write the date and ngā whāinga ako in your book

### Cations

Cation: An atom that has lost electrons to become positively charged

• Pātai Tahi: Write three examples of cations using your knowledge of ions
• Pātai Rua: Use your periodic table to determine what type of elements form cations

### Anions

Anion: An atom that has gained electrons to become negatively charged

• Pātai Tahi: Write three examples of anions using your knowledge of ions
• Pātai Rua: Use your periodic table to determine what type of elements form anions