1.5 Size and mass of atoms

• What does the atomic number represent in an atom?

  Number of protons
• Match the atomic feature with its definition:

  Nucleus ↔️ Central core of atom

  Protons ↔️ Positively charged particles

  Neutrons ↔️ Neutral particles

  Electrons ↔️ Negatively charged particles
• What is the value of 1 atomic mass unit (u) in kilograms?

  1.66 x 10^-27 kg
• Atomic mass is the mass of a single atom, while atomic weight is the weighted average of the masses of all isotopes of an element.
• Atomic weight is the mass of a single atom.

  False
• What is the atomic radius of an atom?

  Half the distance between nuclei
• The atomic radius reflects the extent of the electron cloud
• What particles are found in the nucleus of an atom?

  Protons and neutrons
• Electrons are negatively charged particles that orbit the nucleus
• Isotopes of an element have the same number of protons but different numbers of neutrons.

  True
• How is atomic weight calculated?

  Average mass considering isotopes
• The Van der Waals radius is half the distance between the nuclei of two non-bonded atoms
• Greater shielding increases the atomic size.


  True
• Atomic size decreases across a period due to a consistent shielding effect.
• Atomic mass generally increases across a period due to increasing nuclear charge.

  True
• The structure of an atom consists of a central nucleus containing protons and neutrons, with electrons orbiting the nucleus.
• Isotopes of an element have the same atomic number but different mass numbers.


  True
• The standard unit for measuring atomic mass is the atomic mass unit (u) or dalton (Da).
• Atomic mass includes the mass of protons, neutrons, and electrons.


  True
• Atomic mass is the mass of a single atom, measured in atomic mass units or daltons
• Match the concept with its definition:

  Atomic Mass ↔️ Mass of a single atom

  Atomic Weight ↔️ Weighted average mass of isotopes
• The Van der Waals radius accounts for overlapping electron clouds.

  False
• Match the measurement with its description:

  Atomic Radius ↔️ Distance between bonded atoms

  Van der Waals Radius ↔️ Distance between non-bonded atoms
• Electrons are positively charged particles.

  False
• What is the approximate mass of a proton in atomic mass units?

  1 u
• Atomic mass is measured in atomic mass units or daltons
• Match the concept with its calculation:

  Atomic Mass ↔️ Mass of protons, neutrons, electrons

  Atomic Weight ↔️ Average mass considering isotopes
• What happens to atomic size when nuclear charge increases?

  Decreases
• Across a period, atomic size decreases due to increasing nuclear charge.
• What is the primary factor causing atomic size to increase down a group?

  Increased shielding
• Why does atomic size increase down a group in the periodic table?

  Additional electron shells
• Atomic mass increases down a group because more protons and neutrons are added to the nucleus.