periodicity

• How are elements arranged in the periodic table?

  By proton number
• What do the groups in the periodic table represent?

  Columns where elements have the same number of electrons in their outer shell
• How many electrons do group one elements have in their outer shell?

  One electron
• What happens to the reactivity of group one elements as you go down the group?

  It increases
• What is the trend in atomic radius as you go across period 3?

  The atomic radius decreases
• What causes the decrease in atomic radius across a period?

  Increased nuclear charge pulling electrons closer to the nucleus
• What is the effect of shielding on atomic radius across a period?

  It remains similar, allowing nuclear charge to have a greater effect
• What happens to atomic radius as you go down a group?

  The atomic radius increases
• Why does the atomic radius increase down a group?

  Due to the addition of extra electron shells
• What is the trend in melting points for the first three elements in period 3?

  There is a general increase in melting points
• What type of bonding do sodium, magnesium, and aluminum exhibit?

  Metallic bonding
• Why does magnesium have a higher melting point than sodium?

  Magnesium has a greater positive charge and more delocalized electrons
• What type of structure does silicon have?

  A giant covalent structure
• What determines the melting point of phosphorus?

  Van der Waals forces
• Why does sulfur have a higher melting point than phosphorus?

  Because sulfur has larger Van der Waals forces due to its larger molecular size
• What is the melting point trend for chlorine and argon?

  Chlorine has a higher melting point than argon
• What is ionization energy?

  The minimum amount of energy required to remove one mole of electrons from one mole of atoms in the gaseous state
• What is the effect of shielding on ionization energy?

  More shielding means less energy is required to remove an electron
• How does atomic size affect ionization energy?

  Bigger atoms require less energy to remove an electron due to greater distance from the nucleus
• What happens to ionization energy as you go down a group?

  Ionization energy decreases
• Why does ionization energy decrease down a group?

  Due to increased atomic radius and shielding
• What is the trend in ionization energy as you go across a period?

  Ionization energy increases
• What causes the increase in ionization energy across a period?

  Increased nuclear charge with similar shielding
• What is the significance of the exceptions in ionization energy trends?

  They provide evidence for subshell structure and electron repulsion
• Why does aluminum have a lower ionization energy than magnesium?

  Because its outer electron is in a higher energy subshell and is slightly shielded
• What is the reason for the decrease in ionization energy for sulfur compared to phosphorus?

  Electron repulsion in the same orbital reduces the energy needed to remove an electron
• What are the key concepts related to periodicity that should be included in exam answers?

  • Shielding
  • Nuclear charge
  • Atomic radius
  • Trends in ionization energy
• What are the different blocks of elements in the periodic table?

  • S-block: Elements with outer electrons in the S orbital
  • P-block: Elements with outer electrons in the P orbital
  • D-block: Transition metals with outer electrons in the D orbital
  • F-block: Lanthanides and actinides with outer electrons in the F orbital