How many oxygen atoms are there in 32.8 g of Na2SO4?

Which of the following elements is classified as a chalcogen?

Electron Affinity (EA) generally increases (∆E becomes more negative) from left to right on the Periodic Table. However, P has a lower EA than Si, even though it is further to the right. Which statement below best describes why?

In the resonance form of ozone (O3) shown below, what is the formal charge on the central O atom?

Which of the following elements is classified as an Alkaline Earth Metal?

Visible/UV emission spectroscopy can be used to identify the presence of elements in an unknown sample. Some characteristic wavelengths of common elements are shown below: Ag: 328.1 nm        Fe: 372.0 nm Au: 267.6 nm       K: 404.7 nm Ba: 455.4 nm        Mg: 285.2 nm Ca: 422.7 nm        Na: 589.6 nm Cu: 324.8 nm       Ni: 341.5 nm If an unknown sample is burned and emits light with a frequency of 5.088 x 1014 Hz, which element above is most likely present in the sample?

Which of the following is the correct electron box diagram for a ground-state nitrogen atom?

Which of the following elements is classified as a rare earth metal?

Consider the balanced chemical equation below: 2 NO + O2 → 2 NO2 Which molecular-level representation corresponds to this process?

Which of the following elements has the largest effective nuclear charge (Zeff)?