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Questions

Explanations

1 Which change occurs when an atom in an excited state returns to the ground state?

(1) Energy is emitted.

(2) Energy is absorbed.

(3) The number of electrons decreases.

(4) The number of electrons increases.

2 The valence electrons in an atom of phosphorus in the ground state are all found in

(1) the first shell       (3) the third shell

(2) the second shell (4) the fourth shell

3 Which two elements have the most similar chemical properties?

(1) beryllium and magnesium

(2) hydrogen and helium

(3) phosphorus and sulfur

4 Which phrase describes a compound that consists of two elements?

(1) a mixture in which the elements are in a variable proportion

(2) a mixture in which the elements are in a fixed proportion

(3) a substance in which the elements are chemically combined in a variable proportion

(4) a substance in which the elements are chemically combined in a fixed proportion

5 The formula mass of a compound is the

(1) sum of the atomic masses of its atoms

(2) sum of the atomic numbers of its atoms

(3) product of the atomic masses of its atoms

(4) product of the atomic numbers of its atoms

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