S2.1 Ionic Model

S2.1 Ionic Model

​Common Compounds...

​Common Metals

​Ionic

Covalent

Metallic

​Ionic

Covalent

Metallic

Step 1: ​Test the distilled water (covalent) first.
Step 2: Test the solid salt (ionic).
Step 3: Test the copper electrode (metallic).
Step 4: Does the salt dissolve in water and does the resulting solution conduct?
Step 5: Does the sugar dissolve in water and does the resulting solution conduct?
Step 6: Does the wax dissolve in water & conduct?

​Ionic

Covalent

Metallic

​Heat the solid salt and sugar on a hotplate.
Which melts?

​REVIEW: Ions vs Neutral Atoms

​Cations vs Anions

​If the ion’s charge is positive, we call it a cation. (Hint: the “t” looks like a “+”). If the charge is negative, we call it an anion.

Categorize

Options (11)

He

Cu

O

Cu²⁺

Li⁺

Li

F

F^-

O^2-

Ti³⁺

N^3-

Organize these options into the right categories

Neutral Atom

Cation

Anion

​Predicting Charges: Method 1 - Data Booklet

​Step 1: Simply Look up the charges:

​Advantage: No human error & fast.

Disadvantage: If the question asks you to explain, this won’t help.

Note: Hydrogen gains or loses based on the situation.

Multiple Choice

What is the charge of the common ion of sulfur?

• 1+

• 1-

• 2+

• 2-

• 3-

Multiple Select

Which of the following ions does Manganese form? (There may be more than 1 correct answer)

• Mn⁺

• Mn²⁺

• Mn³⁺

• Mn⁴⁺

• Mn⁵⁺

​G:

​1

​2

​13

​14

​15

​16

​17

​18

​

• The nonmetals gain electrons to fill their valence shell (makes them more stable):

  • Group 14: gain 4 electrons to form 4- ions
    Ex: C forms C^4-

  • Group 15: gain 3 electrons to form 3- ions

  • Ex: N forms N^3-

  • Group 16: gain 2 electrons to form 2- ions

  • Ex: O forms O^2-

  • Group 17: gain 1 electron to form 1- ions.

  • Ex: F forms F-

​The metals lose their valence electrons so that the remaining valence shell is full (more stable).

• Group 1 metals lose 1 valence electron, forming 1+ ions.

  Ex: Li forms Li⁺

• Group 2 metals lose 2 valence electrons, forming 2+ ions.
  Ex: Mg forms Mg²⁺

​Predicting Charges: Method 2 -
Group Numbers

​Advantage: Fast

Disadvantage: Does not work for transition metals.

Multiple Choice

An element is in group 1, what charge will its common ion have?

• +1

• +2

• -1

• -2

Multiple Choice

Nitrogen is a nonmetal in group 15, what ion will it form?

• N⁺

• N^-

• N²⁺

• N^2-

• N^3-

​Predicting Charges: Method 3 - Electron Configuration

​Step 1: Classify it as a nonmetal or metal.

Step 2: Write out its electron configuration.

Step 3: If it’s a nonmetal, it will gain electrons to fill any unfilled sublevels.

​O^2-

​Predicting Charges: Method 3 - Electron Configuration

Step 4: If it’s a metal that isn’t a transition metal, it will lose any electrons in its highest energy level

Na⁺

​Predicting Charges: Method 3 - Electron Configuration

Step 5: If it’s a transition metal, the it loses the 4s electrons first. Other ions are formed by losing the number of 3d electrons that correspond to what is in the data booklet.

​Advantage: Best method of explanation for all elements.

Disadvantage: Takes longer.

Multiple Choice

What ion will the metal aluminum form?

• Al⁺

• Al²⁺

• Al³⁺

• Al⁴⁺

Multiple Choice

What ion will the non-metal bromine form?

• Br^-

• Br^2-

• Br^3-

• Br^4-

• Br^5-

​Monatomic vs Polyatomic Ions

​Ions made of one atom are called monatomic. If they are made of more than one atom, they are called polyatomic ions. They can be cations or anions.

Categorize

Options (8)

Li⁺

Fe³⁺

Br^-

S^2-

NO₃^-

NH₄⁺

CO₃^2-

SO₄^2-

Organize these options into the right categories

Monatomic

Polyatomic

Memorization

The IB expects you to memorize the formula (including charge) and name of the following 7 polyatomic ions:

Match

Match the following

• Carbonate

• Hydrogencarbonate

• Hydroxide

• Ammonium

CO₃^2-

HCO₃^-

OH^-

NH₄⁺

• CO₃^2-

• HCO₃^-

• OH^-

• NH₄⁺

Multiple Choice

Which of the following is the phosphate ion?

• PO₄^3-

• PO₄^2-

• PO₃^4-

• PO₃^2-

• PO₄³⁺

Draw

Write the chemical formula of the sulfate ion.

​Nature of the Ionic Bond

​Formation of Ionic Bonds

​Result from a transfer of electrons, usually from a metal to a nonmetal.

​Criss Cross Rule (Empirical Formula for Ionic Compounds)

​This is a shortcut to save time.
Step 1: Write the cation on the left, anion on the right.
Step 2: The numbers swap to become subscripts, get rid of the +/- signs.
Step 3: If a polyatomic ion is given a subscript, enclose it in brackets first.
Step 4: If the subscripts you criss-crossed can be simplified, do it!

Draw

What is the formula for the compound made from the Na⁺ and S^2- ions?

Draw

What is the formula for the compound made from the Cu³⁺ and O^2- ions?

Draw

What is the formula for the compound made from the Cu²⁺ and O^2- ions?

Draw

What is the formula for the compound made from the Al³⁺ and NO₃^- ions?

Draw

What is the formula of the compound made from calcium reacting with fluorine?

Draw

What is the formula of the compound made from lithium reacting with sulfate?

Draw

What is the formula of the compound made from aluminum reacting with phosphate?

​Naming Rules

​Your teacher will demo how to name these:
1) Na₂S
2) CuO
3) NH₄Cl
4) Ca(NO₃)₂

​Naming Rules

​Your teacher will demo how to name these:
1) Na₂S
2) CuO
3) NH₄Cl
4) Ca(NO₃)₂

​Names to Formulas

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​Giant Ionic Lattice

​Ionic compounds form giant ionic lattices in which ions of opposite charges surround one another and form ionic bonds. To us, they look like crystals.

​The giant ionic lattice allows us to explain the physical properties of ionic compounds.

​Lattice Enthalpy (Energy)

​Lattice enthalpy (energy) measures how much energy is needed to break all the ionic bonds in one mole of an ionic compound into gaseous ions.

​Examples: NaCl(s) → Na⁺(g) + Cl^-(g)              MgCl₂(s) → Mg²⁺(g) + 2Cl^-(g)

​In other words, lattice enthalpy measures the strength of the ionic bond or how difficult it is to overcome the electrostatic attraction between ions.

​Factors Affecting Lattice Enthalpy

​Analyze the lattice enthalpy values (larger value = stronger ionic bonding) in Table 16 of the Data Booklet. Try to connect your explanations to electrostatic attraction.

Drag and Drop

Factor 1: As the ionic radius ​

Placeholder

, the lattice enthalpy ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

increases

decreases

Multiple Choice

Factor 2: Lattice enthalpy decreases as ionic radius increases primarily because:

• The larger ionic radii correlate to more electron repulsion, decreasing electrostatic attraction.

• The smaller distance between larger ions causes weaker electrostatic attraction.

• The larger distance between larger ions causes weaker electrostatic attraction.

• The larger ionic radii correlate to higher nuclear charge, leading to weaker electrostatic attraction.

Drag and Drop

Factor 2: As the ionic charge​ , the lattice enthalpy ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

increases

decreases

Multiple Choice

Factor 2: Lattice enthalpy increases as ionic charge increases primarily because

• Higher charge means fewer energy levels, causing stronger electrostatic attraction.

• Higher charge causes repulsion between ions, increasing their attraction.

• Higher charge means fewer electrons, so they is less electron-electron repulsion.

• Higher charge causes stronger electrostatic attraction between ions.

​Ionic Physical Property 1: Solid at Room Temp

​Ionic compounds are solid at room temperature because of their high lattice enthalpy means a high temperature is needed before the ionic bonds can be weakened enough to melt or vaporize.

For example, in NaCl, each Na⁺ and each Cl^- ion is surrounding by 6 other ions. Thus you need to weaken or break a lot of bonds to get an ion to be free of the giant ionic lattice.

​Ionic Physical Property 2: Low Volatility

Volatility refers to the tendency of a substance to vaporise. 

• A substance with high volatility has weak attractions between particles, leading to a high vapor pressure.

• Ionic compounds have low volatility because the strong attractions between ions leads to a low vapor pressure (the ions stay in the lattice).

​Ionic Physical Property 3: Conductivity

​In order for a substance to conduct electricity at a state, it must have FMCPs (Freely Moving Charged Particles). Let’s explore these…

Sugar and Salt Solutions - Solutions | Ionic | Covalent - PhET Interactive Simulations

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​Ionic Physical Property 4: Solubility

​Many ionic compounds are soluble in polar solvents like water because the positive and negative ends of the solvent molecule are attracted to the + and - charges of the ions. 

​Note: Not all ionic compounds are soluble in water. Several other factors play into whether it is overall favorable.

​We can see this process in the Micro tab of the simulation on the next slide.

Sugar and Salt Solutions - Solutions | Ionic | Covalent - PhET Interactive Simulations

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