1. The atomic number of an atom is the number of ______ in the atom's nucleus.

2. Elements are made from a single type of _______.

3. What element has an atomic number of 1?

4. What are the different physical forms of an element called?

5. According to the article, how many elements are there in the current periodic table?

6. To what family of elements do the elements helium, neon, and argon belong to?

7. What family of elements has only one electron in the outer shell making them very reactive?

8. What is the name of the chart that scientists use to keep track of the elements?

9. What is the most common element in the universe?

10. What are atoms of the same element that have a different number of neutrons called?