atomic structure & properties practice

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

How many neutrons does uranium-239 have

• 92
• 147
• 239
• 331

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 atoms that have different mass numbers?

• They do not have the same number of protons.
• Their atoms have different number of neutrons.

• They are isotopes of oxygen.
• The have the same number of neutrons

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.

The dense center region of an atom

• electron cloud
• core
• nucleus
• centrino

An atom has 10 protons and a mass number of 18. It has __ neutrons

• 10
• 18
• 28
• 8

How many protons are present in a phosphorus atom with a mass number of 31?

• 15
• 16
• 31
• 46