Understanding the atom

Based on his research of the atom, James Chadwick concluded that

• a cathode ray has a negative charge

• the electrons are found in an electron cloud

• the nucleus contains neutrons as well as protons

• the mass of an atom is concentrated in its center

Two atoms of different elements will definitely have different numbers of

• nuclei

• protons

• neutrons

• electrons

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What allowed scientists to see an individual atoms for hte first time?

• cathode ray tubes

• photographic plates

• compound microscopes

• scanning tunneling microscopes (STM)

An ion that has a negative charge is formed when an atom

• loses neutroons

• loses electrons

• gains neutrons

• gains electrons

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Two neutral atoms that have the same atomic number and different mass numbers are

• ions

• isotopes

• alpha particles

• different elements

The ____ is a weighted average that reflects the abundance of different isotopes.

• ions

• average atomic mass

• mass number

• elements

The ____ is determined by adding the number of protons and neutrons in an atom.

• neutrons

• mass number

• atomic number

• elements

The element's ____ and the number of protons in the nucleus of its atoms are always the same.

• atomic number

• mass number

• average atomic mass

• protons

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_____ are atoms of the same element that have different numbers of neutrons.

• Elements

• Protons

• Ions

• Isotopes

Alpha decay releases ____

• nothing

• 1 proton

• alpha particle

• high energy electron

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