Why do elements in the same periods have diffrent properties​

Elements in the same period have different properties because the number of valence electrons in their outermost shells differ. In a given column or group, all elements have the same number of electrons in their outermost shells.

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astronomers such as edwin hubble.

away from the curb

explanation:

the wheels would then hit the curb if it started to rolling, decreasing the chance of an accident.