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.