Understanding the Periodic Table and Isotopes

What does the atomic number of an element represent?

• The number of neutrons in an atom

• The number of protons in an atom

• The total number of nucleons in an atom

• The average mass of the element

What is the significance of the decimal places in the mass number on the periodic table?

• They represent the number of electrons

• They show the number of isotopes

• They indicate the average atomic mass

• They are a result of measurement errors

Why can't we simply average the coursework and final exam scores to get a student's final grade?

• Because the coursework score is always lower

• Because the final exam score is always higher

• Because the scores are not percentages

• Because the coursework and final exam have different weightings

What is an isotope?

• An element with a different number of electrons

• An element with a different number of protons

• An element with a different atomic number

• An element with a different number of neutrons

What is the mass number of an isotope?

• The average mass of the isotope

• The number of protons in the isotope

• The number of neutrons in the isotope

• The total number of protons and neutrons in the isotope

Which isotope of magnesium is the most abundant in nature?

• Magnesium-27

• Magnesium-26

• Magnesium-25

• Magnesium-24

How is the average atomic mass of an element calculated?

• By using a weighted average of all naturally occurring isotopes

• By taking the mass of the most abundant isotope

• By adding the masses of all isotopes and dividing by the number of isotopes

• By averaging the atomic numbers of all isotopes

What is the relative abundance of magnesium-25 in nature?

• 78.7%

• 33%

• 10%

• 11.3%

Why might the calculated average atomic mass not match the periodic table exactly?

• Because the periodic table is outdated

• Because of the use of relative atomic mass

• Because isotopes are not real

• Because of rounding errors

What does the term 'relative atomic mass' refer to?

• The mass of an element compared to hydrogen

• The average mass of an element's isotopes

• The mass of the most common isotope

• The mass of an element compared to carbon