Atomic structure

The mass number of an element that has 18 protons, 18 electrons, and 19 neutrons is _____.

• 12.5
• 13
• 25
• 37

The atomic number of an element that has 9 protons, 9 electrons, and 10 neutrons is _____.

• 9
• 10
• 19
• 28

If the number of electrons in an atom changes you make a(n) __________________.

• ion
• isotope
• new element
• isomer

Which statement about subatomic particles is true?

• Protons, neutrons, and electrons all have about the same mass.
• Unlike protons or neutrons, electrons have no mass.
• Neutrons have no charge and no mass.
• An electron has far less mass than either a proton or neutron.

Which of the following is unique for any given element?

• the number of neutrons
• the charge on the electrons
• the number of protons
• the mass of a neutron

Which statement is true about oxygen-17 and oxygen-18?

• They do not have the same number of protons.
• Their atoms have an identical mass.
• They are isotopes of oxygen.
• The have the same mass number.

The mass number of a single atom  is

• the sum of the protons and neutrons in the atom.
• twice the number of protons in one atom of the element.
• a ratio based on the mass of a carbon-12 atom.
• a weighted average of the masses of the element’s isotopes.

Two isotopes of carbon are carbon-12 and carbon-14.  These isotopes differ from one another by two protons.

• true
• false

Changing the number of neutrons in an atom changes its...

• element type.
• mass.
• charge.
• atom type.

When there are the same number of protons and electrons in an atom, that atom is a...

• positive ion.
• negative ion.
• unstable isotope.
• neutral atom.