1.5 Size and mass of atoms

• How does atomic size change across a period in the periodic table?

  Decreases
• What happens to the atomic radius when the nuclear charge increases?

  Decreases
• What are the primary components that determine atomic mass?

  Protons and neutrons
• What does atomic size refer to?

  Diameter or radius of atom
• How does atomic size relate to chemical reactivity?

  Larger atoms are more reactive
• Atomic radius increases with the number of electron shells.


  True
• What primarily determines the atomic mass of an atom?

  Protons and neutrons
• Steps to calculate average atomic mass

  1️⃣ Multiply the mass of each isotope by its relative abundance

  2️⃣ Sum the products
• What is the mass number of carbon-12?

  12
• What is the significance of atomic size trends in the periodic table?

  Chemical reactivity
• Larger atoms are more chemically reactive due to having more valence electrons.


  True
• Describe the general trends in atomic size across the periodic table.

  1️⃣ Atomic size increases down a group

  2️⃣ Atomic size decreases across a period
• Atomic mass is expressed in atomic mass units
• Atomic size generally increases down a group and decreases across a period
• Larger atoms are more chemically reactive because they have more valence electrons
• What effect does increasing nuclear charge have on atomic radius?

  Decreases atomic radius
• Atomic mass is expressed in atomic mass units
• What is the average atomic mass of an element with two isotopes: Isotope A with 10 amu and 75% abundance, and Isotope B with 12 amu and 25% abundance?

  10.5 amu
• Match the concept with its definition:

  Atomic mass ↔️ Weighted average of isotope masses

  Mass number ↔️ Total number of protons and neutrons
• Atomic size generally increases down a group
• As the number of electron shells increases, the atomic radius also increases
• The increasing number of electron shells down a group increases the atomic radius.


  True
• Match the atomic component with its properties:

  Protons ↔️ Positively charged

  Neutrons ↔️ Neutral charge
• Atomic size increases down a group in the periodic table.

  True
• Trends in atomic size across the periodic table

  1️⃣ Increases down a group

  2️⃣ Decreases across a period
• Match the trend in atomic size with its effect on the periodic table:

  Down a group ↔️ Larger atoms

  Across a period ↔️ Smaller atoms
• Protons have a mass of approximately 1 atomic mass unit.


  True
• Atomic mass is the total number of protons and neutrons in an atom.

  False
• Atomic mass is measured in atomic mass units