Q1
What does an atom consist of?
AA nucleus and electrons
BOnly electrons
COnly a nucleus
DNothing specific
ICSEClass 7 (ICSE)ScienceCh 11 · Topic 2
Practice and Revision - Atoms, Molecules and Radicals
Let us practise and revise what we learned about atoms, molecules and radicals. Atoms are the basic units of elements, molecules form when a
Core concept
An atom consists of a nucleus (containing protons and neutrons) surrounded by electrons, forming the basic building block of matter.
How it works
A molecule forms when two or more atoms bond together, like O₂ (oxygen molecule) or H₂O (water molecule).
Why it matters
A radical, like the hydroxide ion (OH⁻), is a group of atoms that behaves as a single unit and carries a charge in chemical reactions.
Key detail
Understanding atoms, molecules, and radicals is fundamental to understanding chemical reactions and how substances combine.
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Quick notes
• An atom has a nucleus with protons and neutrons.
• Electrons surround the nucleus.
• A molecule forms when atoms bond together.
• Examples: O2, H2O.
• A radical is a group of atoms acting as one unit.
• Example: hydroxide ion (OH-).
• Radicals carry a charge in reactions.
• These concepts are fundamental to chemistry.