Atoms of which element have two protons and two electrons?
a. hydrogen
b. helium
c. lithium
d. carbon

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

Calculate the estimated density of each ball. use the formula d = m/v where d is the density, m is the mass, and v is the volume. record your calculations in table a of your student guide. given that the density of water is 1.0 g/cm3, make a prediction about whether each ball will float in water. record your prediction in table a. what is the estimated density of the table tennis ball? record your answer to the nearest hundredth

Which of these features are formed when hot groundwater is forced out through cracks in the earth's surface?