Explanation:
Take shelter in a hard wall building
Close doors and windows cut off ventilation
Answer:
They have similar properties, because they share similar amounts of electrons in their outer shell, valence electrons! This means they will only be able to interact with other elements with those electrons so they often show similar properties.
Explanation:
Atoms of the same element with different mass numbers are called isotopes
Their atomic number increases
Well people say the world's going to end soon so people need to find another planet to live on they're thinking about Mars at the moment