How Atoms Combine
Atoms combine with other atoms by losing, gaining, or sharing electrons so that they can become more stable.
Practice This ConceptMain explanation
Teacher explanation
The outermost shell of an atom controls its combining behaviour. Atoms with incomplete outer shells tend to combine in a way that gives them a stable electronic arrangement, often similar to noble gases.
Example
Sodium loses one electron and chlorine gains one electron to form sodium chloride, while two hydrogen atoms share electrons with oxygen to form water.
Simple analogy
Outer shell decides bonding behaviour.
Common confusion
Students often say atoms combine simply because they want to become bigger. The better exam reason is stability of the outermost shell.
Exam tip
Mention outermost-shell stability and the method of combination: loss, gain, or sharing of electrons.
Answer writing and exam use
1-mark use
Write the exact meaning of how atoms combine in one clean line.
2-mark use
Define how atoms combine and add one example or condition.
3-mark use
Explain how atoms combine, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
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