Tom tells Greta that his father, an astronomer, is planning a scientific experiment to study another galaxy. Using a powerful telescope, Tom's father will record data of shifts in light patterns and track their different sources every 30 seconds. He will later study the data. Greta says that this is not an experiment. Which of these reasons supports Greta's statement? It is not performed in a lab.

There are too many variables.

It does not have a control group.

It uses only theoretical predictions.

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

Express the following number in scientific notation. 0.026890 =

What causes different colors to appear in the sky? the absorption of light by air molecules the reflection of light by bodies of water the greenhouse effect in earth's atmosphere the scattering and reflection of light by dust particles