Helium has two protons, two neutrons and two electrons. what is the charge of this atom?
a. 0
b. 2
c. 4
d. more information is needed.

This chart lists four kinds of polymers and their sources. what can be known about all four polymers, despite their differences? they come from living things. they share ionic carbon bonds. they are at least 100 monomers long. they are made of repeating subunits.

What happens to isotopes that are unstable?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation: