Question 1
Why does losing an electron produce a positive ion?
Need a hint for Question 1?
The proton number identifies an element.
Check Question 1
There are now more protons than electrons.
STUDENT SPACE · TOPIC 1
Compounds and ions
Distinguish mixtures from compounds and explain how ions form.
The essentials
- Compounds contain different elements chemically combined in a fixed ratio. Mixtures have variable composition and can be separated physically.
- A chemical change forms new substances. A physical change does not.
- Positive ions form when atoms lose electrons. Negative ions form when atoms gain electrons. The nucleus stays unchanged.
Key vocabulary
| English | Chinese |
|---|---|
| compound | 化合物 |
| cation | 阳离子 |
| anion | 阴离子 |
Quick practice
Try each question before opening its hint or answer. Use paper for calculations and diagrams.
Question 2
An oxygen atom gains two electrons. Give its ion symbol and electronic configuration.
Need a hint for Question 2?
Add two electrons to the eight in a neutral oxygen atom.
Check Question 2
O²⁻, with electronic configuration 2,8.
Question 3
Explain why Na⁺ is still sodium.
Need a hint for Question 3?
What determines an element's identity?
Check Question 3
It still has 11 protons. The proton number identifies the element.
Use the matching chapter worksheet. Attempt independently, compare your reasoning with your partner, then bring unresolved questions to your teacher.
PREDICT · TRY · EXPLAIN · 3–5 MINUTES
Ions, lattices and conductivity
Predict which states conduct. Change the state, then explain what carries charge.
1 · Form the ions
Na has electron arrangement 2,8,1. Cl has 2,8,7.
Na (2,8,1) → e⁻ → Cl (2,8,7)
Predict the charge on each atom after the transfer.
2 · Test conductivity
Na⁺Cl⁻Na⁺Cl⁻Na⁺Cl⁻Cl⁻Na⁺Cl⁻Na⁺Cl⁻Na⁺Na⁺Cl⁻Na⁺Cl⁻Na⁺Cl⁻
Predict: can charged particles move through this sample?
Molten salt is melted; aqueous salt is dissolved in water. These are different processes. This schematic shows mobility, not a full electrolysis circuit.