Rutherford postulated the existence of some neutral particle having mass similar to proton but there was no direct experimental evidence. Several theories and experimental observations eventually led the discovery of neutron.
Answer:
The rows on the periodic table are called periods. All the elements in a period have valence electrons in the same shell. The number of valence electrons increases from left to right in the period. When the shell is full, a new row is started and the process repeats.
Explanation:
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