During the Precambrian, Earth's first atmosphere is theorized to have been composed of a poisonous mixture of helium and hydrogen gases. When Earth's crust began to cool, the makeup of the atmosphere changed.

Yes.

Explanation:

Yes, early Earth's atmosphere was formed from the poisonous mixture of helium and hydrogen gases. But with the passage of time when Earth's crust began to cool, the composition of the atmosphere changed and carbondioxide and water concentration in the atmosphere increases due to carbondioxide gas emission from the volcanoes and evaporation of water from water bodies present on the surface of earth.