Grade 9 · Ions and Our Health · Ionic Compounds and Health
Ionic Bonding
How oppositely charged ions attract to build giant ionic lattices.
Learning objectives
- Describe the transfer of electrons in ionic bonding.
- Explain why ionic compounds have no overall charge.
- Relate lattice structure to properties such as high melting point.
NGSS alignment
HS-PS1-4
Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
HS-PS1-2
Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
HS-PS1-3
Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.
MYP criteria
- Criterion A — Knowing and Understanding
- Criterion B — Inquiring and Designing
ENGAGE
Why is salt so hard to melt?
Think about it
Candle wax melts in your hand, but table salt needs about 801 degrees C. What holds salt together so strongly?
EXPLAIN
Electron transfer and lattices
In ionic bonding a metal atom transfers electrons to a non-metal atom. The oppositely charged ions then attract each other strongly in all directions, forming a giant regular lattice.
- Na loses 1 electron; Cl gains 1 electron.
- Na+ and Cl- attract electrostatically.
- The ratio of ions balances the charges, so the compound is neutral overall.
- Many strong attractions must be broken to melt the lattice - hence the high melting point.
Watch out
Solid ionic compounds do not conduct electricity: the ions are locked in place. They conduct when molten or dissolved, because then the ions can move.
Interactive simulation · PhET
Atomic Interactions
Explore how attraction and repulsion change with distance between particles.
While you explore
- At what distance is attraction strongest?
- How does this relate to ions holding together in a lattice?
Key vocabulary
- Ionic lattice
- A regular 3D arrangement of alternating positive and negative ions.
Practice questions
0/2 correct
Level 1
In ionic bonding, electrons are...
Level 2
Why do ionic compounds have high melting points?
MYP criterion tasks
Level 4 · Criterion B
Design an investigation to determine how the concentration of a salt solution affects its electrical conductivity.
Reflect & track
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