A physical change is any change in a substances form that does not change its chemical makeup. Examples of physical changes are breaking a stick or melting ice. A chemical change occurs when atoms of a substance are rearranged, and the bonds between the atoms are broken or formed. HOPE THIS HELPS!!
Answer:
20 km
Explanation:
he walks 10 km + another 10 km so 20 :)
They both have two electron shells. Period indicates number of shells.
I mole is the answer I believe