An isotope refers to elements with the same atomic number but different numbers of neutrons.

Hydrogen is the most abundant element in the universe.

Transition elements play an important role in chemical reactions.

My friend lives in Arkansas.

He has the spirit of mutual concession.

You can put out oversized garbage every first Saturday of the month.

I love histology classes.

My grandmother is very kind.

My grandfather is healthy and living a long life.

He is the main organizer of this event.