Hmh Chemistry

Chlorine has a total of 17 electrons and 7 valence electrons. Why are these two numbers different?

• Valence electrons are the electrons in the innermost orbital.

• Valence electrons are the electrons in the outermost energy shell.

• Some electrons are located in the nucleus of the atom.

• Some electrons are located outside the atom.

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Why does the mass number for an element differ from the average atomic mass for that element?

• The mass number only accounts for the number of protons, while the average atomic mass only accounts for the average number of neutrons.

• The mass number accounts for the number of protons and neutrons, while the average atomic mass only accounts for the average number of protons.

• The mass number accounts for the mass of each isotope. The average atomic mass is a weighted average of the number of neutrons.

• The mass number only accounts for the mass of protons and neutrons, while the average atomic mass is a weighted average of the masses of the isotopes.

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Strontium has an atomic number of 38 and an atomic mass number of 88. Therefore it has how many PROTONS?

• 38

• 50

• 88

Strontium has an atomic number of 38 and an atomic mass number of 88. Therefore it has how many NEUTRONS?

• 38

• 50

• 88

Strontium has an atomic number of 38 and an atomic mass number of 88. Therefore it has how many ELECTRONS?

• 38

• 50

• 88

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Electron-dot notation shows only the electrons in which part of the atom?

• innermost

• outermost

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The electrons in the outermost energy shell of an atom are called _______.

• valence electrons

• orbital electrons

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The valence electrons __________ involved in chemical reactions.

• are

• are not

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Elements with a full outer energy shell are typically _________.

• very reactive

• unreactive

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A scientist picks up a sample of an element. She thinks it might be a metal. Which of the following properties would support her conclusion? Select all correct answers.

• element is shiny

• element is dull

• element partially conducts electricity

• element is a good conductor of electricity

• element is very brittle