Atomic Masses

Question 1

How is the mass of an atom found?

Answer 1

Comparing masses of atoms to carbon-12, using idea of reactive atomic mass

Question 2

What is the unit for atomic mass?

Answer 2

Unified atomic mass unit: u

Question 3

When is the relative isotopic mass the same as the mass number?

Answer 3

For isotopes

Question 4

What assumptions are made when weighing atoms?

Answer 4

• Neglected tiny contribution electrons make
• Both proton and neutrons have masses of 1.0u

Question 5

What is the relative atomic mass of an element?

Answer 5

Weighed mean mass of an atom of an element compared with 1 twelfth of mass of a carbon-12 atom

Question 6

What contributions do isotopes make to the overall mass?

Answer 6

• Percentage abundance of isotope
• Relative mass of isotope

Question 7

What is the relative isotopic mass?

Answer 7

Atomic mass of isotope compared with 1 twelfth of carbon-12 atom mads

Question 8

What is the relative molecular mass?

Answer 8

All relative atomic masses of each atom making up a molecule added together

Question 9

Which compounds don’t exist as simple molecules?

Answer 9

Giant structures

Question 10

Why is the relative formula mass better than the relative molecular mass when weighing giant structures?

Answer 10

Involve adding masses of thousands of atoms together, giving an extremely large number

Question 11

What is a formula unit?

Answer 11

Whatever is written in chemical formula