Henry Cavendish, of the Royal Society of London, discovered that water was composed of: two parts “inflammable air” and one part “dephlogisticated air” two parts “dephlogisticated air” and one part “fixed air” two parts “fire air” and one part “dephlogisticated air” two parts “fixed air” and one part “inflammable air” two parts “fixed air” and one part “phlogiston”

A. The first shell corresponds to the first energy level, and it can hold up to 2 electrons. Hydrogen has one proton, so it has 1 electron and one vacancy. A helium atom has 2 protons, 2 electrons, and no vacancies. B. The second shell corresponds to the second energy level, and it can hold up to 8 electrons. Carbon has 6 electrons, so its first shell is full. Its second shell has 4 electrons and four vacancies. Oxygen has 8 electrons and two vacancies. Neon has 10 electrons and no vacancies. C. The third shell corresponds to the third energy level, and it can hold up to 8 electrons. A sodium atom has 11 electrons, so its first two shells are full; the third shell has one electron. Thus, sodium has seven vacancies. Chlorine has 17 electrons and one vacancy. Argon has 18 electrons and no vacancies. Figure It Out: Which of these models have unpaired electrons in their outer shell?

Oxygen (O) is a(n) _______; the oxygen we breathe (O2) is a(n) _______; and the carbon dioxide we exhale is a(n) _______. a. compound; molecule; element b. atom; compound; element c. element; atom; molecule d. atom; element; molecule e. element; molecule; compound

Jenny mixes up a batch of pancake batter, then stirs in some chocolate chips. As she is waiting for the first few pancakes to cook, she notices the chocolate chips sinking to the bottom of the clear glass mixing bowl. The chocolate- chip batter is an example of a________. solvent solute solution suspension

A molecule into which a radioisotope has been incorporated can be used as an ____________. a. compound c. salt b. tracer d. acid

Which of the following statements is not true? Water is polar Water stabilizes temperature Water is essential for life Water is the most abundant molecule in the Earth’s atmosphere.

Discuss Concepts You place a metal pan full of water on the stove and turn on the heat. After a few minutes, the handle is too hot to touch but the water is only warm. How do you explain this observation?

An _________ substance repels water. a. acidic c. hydrophobic b. basic d. polar

Explain why water is an excellent solvent.

A molecule that donates electrons becomes _________, and the one that accepts the electrons becomes ________ . a. reduced; oxidized c. oxidized; reduced b. ionic; electrified d. electrified; ionic