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?
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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