2.1 The Nuclear Atom

Open Ended

If the number of protons and electrons in an atom are the same, why can’t we define the atomic number in terms of the number of electrons in the atom?

Multiple Choice

An atom of phosphorus has an atomic number of 15 and a mass number of 31. How many neutrons does it contain?

• 15

• 16

• 31

• 46

Multiple Choice

Complete the following sentence:

'Different isotopes of the same element have...'

• ...the same number of protons, but differing numbers of neutrons and electrons.

• ...the same number of neutrons, but differing numbers of protons and electrons.

• ...the same number of protons and neutrons, but differing numbers of electrons.

• ...the same number of protons and electrons, but differing numbers of neutrons.

Multiple Choice

Four isotopes of lead include lead-204, lead-206, lead-207, and lead-208.  The average atomic mass of lead is 207.2.  Which isotope of lead is likely to be the most abundant.

• 204

• 208

• 206

• 207

Multiple Choice

Element Z has 2 natural isotopes. One isotope has a mass of 15.0 amu and a relative abundance of 30%. The other isotope has a mass of 16.0 amu and a relative abundance of 70%. Estimate the average atomic mass for this one element.

• 15.0 amu

• 15.7 amu

• 16.0 amu

• 16.9 amu