1.2.1 Arrangement of elements

• What is the atomic number of an element defined as?

  Number of protons
• What does the electron configuration of an atom describe?

  Electron distribution
• The period number in the Periodic Table corresponds to the highest occupied electron shell
• Atomic radius decreases from left to right across a period.


  True
• What are periodic trends driven by in the Periodic Table?

  Increasing nuclear charge
• What happens to ionization energy as you move down a group in the Periodic Table?

  Decreases
• What does the mass number of an atom represent?

  Protons and neutrons
• Steps to describe the arrangement of elements in the Periodic Table based on electron configurations:

  1️⃣ Assign electron shells

  2️⃣ Distribute electrons among shells

  3️⃣ Identify valence electrons
• Electron shells are numbered 1, 2, 3, and so on, moving further from the nucleus.


  True
• The period number in the Periodic Table corresponds to the highest occupied electron shell
• What are groups in the Periodic Table?

  Vertical columns
• Periods in the Periodic Table are arranged vertically.

  False
• Periodic trends are influenced by the number of protons and the arrangement of electrons.


  True
• Electronegativity increases down groups.

  False
• The Periodic Table classifies elements into three main categories: metals, nonmetals, and metalloids.
• The atomic number determines an element's position in the Periodic Table.


  True
• What does the period number in the Periodic Table correspond to?

  Highest occupied shell
• Elements in the same group share the same number of valence electrons
• Periodic trends are driven by the increasing nuclear charge
• Electronegativity increases from left to right across a period.

  True
• The atomic number of an element is the number of protons in its nucleus.

  True
• Why is the atomic number unique to each element?

  Number of protons
• Valence electrons are located in the outermost shell
• How many electrons can the third electron shell hold?

  18
• Elements in the same group have the same number of valence electrons.


  True
• Elements in the same group share the same number of valence electrons in their outermost shell.
• Match the feature with the corresponding term:

  Horizontal rows ↔️ Periods

  Vertical columns ↔️ Groups
• As you move down a group, the atomic radius of elements increases because additional electron shells are added.
• The atomic radius decreases as you move across a period.


  True
• Metalloids are located on the left side of the Periodic Table.

  False
• The atomic number is unique to each element
• Electron shells are numbered to represent different energy levels
• What does the group number in the Periodic Table indicate about an element?

  Valence electrons
• What happens to ionization energy as you move down a group?

  Decreases
• Atomic radius decreases from left to right across a period
• The increasing nuclear charge and decreasing shielding of valence electrons impact chemical reactivity
• The symbol for the atomic number is Z
• What do electron shells represent in an atom?

  Energy levels
• How many electrons can the first electron shell hold?

  2
• Match the period number with the shell occupied and the number of elements in that period:

  Period 1 ↔️ Shell 1, 2 elements

  Period 2 ↔️ Shell 2, 8 elements

  Period 3 ↔️ Shell 3, 8 elements