What is the center of an atom called?

What part of an atom has a positive charge?

How many elements are there in the world?

What two things are found in the nucleus of an atom?

What have a negative charge?

What have a neutral charge (or no charge)?

What part of the atom is the most dense, and where most of the mass is found?

An atom is made up of mostly ___________________________

A substance that cannot be broken down into anything simpler is _____________________.

A substance made up of two or more different elements is _______________________.

An example of a compound is _________________.

An example of an element is _______________ (pick all that apply).