How were noble gases discovered?

If an isotope has an atomic number of 8 and a mass number of 18 how many neutrons

The compound methyl butanoate smells like apples. Its percent composition is 58.8% C, 9.8% H, and 31.4% O, and its molar mass is 102 g/mol. Calculate the empirical and molecular formulas for this compound.

Doppler shifted hydrogen absorption lines are seen in the spectrum of a star. The hydrogen line at 656.28 nm is seen to be shifted to 656.08 nm. Is the star moving towards or away from us, or can we not tell?

In your own words, describe two conditions that are necessary for an eclipse to occur

A 0.055 mol sample of formaldehyde vapor, CH2O, was placed in a heated 500 mL vessel and some of it decomposed. The reaction is CH2O (g) H2 (g) + CO (g) At equilibrium, the CH2O (g) concentration was 0.051 mol L-1.

What is the mass (in grams) of 9.09x10^24 molecules of methanol (CH3OH) ? AND How many moles of N are in 0.183g of N2O?

What are the basic building blocks of matter? A) molecules B) atoms C) electrons D) compounds

How does an atom with too few neutrons relative to protons undergo radioactive decay? * by converting proton to a neutron by converting a neutron to a proton by emitting an alpha particle

What is the chemical formula for the compound formed between sodium and iodine?

8. Write a balanced chemical equation showing how you could prepare each of the following salts from an acid-base reaction: KNO3, NaBr, and Cas.