Periodicity

• What is a transition metal?

  An element with a partly filled d-orbital
• Which d-block elements are not transition elements?

  Zinc and scandium
• What is periodicity?

  Characteristics of elements showing a repeating pattern with increasing atomic number
• What type of structure do Na, Mg, and Al have?

  Giant metallic structures
• Why does the melting point increase for Na, Mg, and Al?

  More outer shell electrons increase electrostatic attraction between positive metal ions + delocalised electrons
• What type of structure does silicon have?

  Giant covalent molecule/macromolecular
• What is the standard state formula for phosphorus?

  P$_4$
• What is the standard state formula for sulfur?

  S$_8$
• What type of forces do simple molecules have?

  Weak van der Waals forces between molecules
• What happens to atomic radius across Period 3?

  It decreases
• Why does atomic radius decrease across a period?

  Increased nuclear charge pulls electrons closer
• What are the exceptions to the trend of first ionisation energy?

  Group 2-3 and 5-6
• What causes the dip in first ionisation energy between groups 2 and 3?

  Transition from S orbital to P orbital
• What causes the dip in first ionisation energy between groups 5 and 6?

  Repulsion between paired electrons in orbitals
• Why does it become more difficult to remove electrons in successive ionisation energies?

  Positive ion has stronger attraction to electrons
• What indicates a big jump in successive ionisation energies?

  Breaking into an inner shell
• How can you identify which group an element is in using ionisation energies?

  The element is in the group before the big jump
• How are elements arranged in the periodic table?

  By proton number, not mass number
• What do elements in the same group have in common?

  Same number of outer shell electrons
• What do elements in the same period have in common?

  Same number of electron shells
• What happens to atomic radius as you go across period 3?

  Atomic radius decreases
• Why does atomic radius decrease across a period?

  Increased nuclear charge pulls electrons closer
• What happens to atomic radius as you go down a group?

  Atomic radius increases
• Why does atomic radius increase down a group?

  Extra electron shells are added
• What is the trend in melting points for metals in period 3?

  Melting points generally increase
• Why does magnesium have a higher melting point than sodium?

  Magnesium has a higher positive charge
• Why does silicon have a high melting point?

  Many strong covalent bonds require high energy to break
• Why does sulfur have a higher melting point than phosphorus?

  It has larger van der Waals forces between molecules
• What is the state of argon at room temperature?

  Monoatomic gas
• What happens to ionisation energy as you go down a group?

  Ionisation energy decreases
• Why does ionisation energy decrease down a group?

  Outer electrons are further from the nucleus
• What happens to ionisation energy as you go across a period?

  Ionisation energy increases
• Why does ionisation energy increase across a period?

  More protons increase nuclear attraction
• What is the significance of the exceptions in ionisation energy trends?

  They indicate subshell structure and electron repulsion
• What are the trends in melting points across period 3?

  1. Sodium, magnesium, aluminum: increase
  2. Silicon: much higher due to covalent bonds
  3. Phosphorus: lower due to van der Waals forces
  4. Sulfur: higher than phosphorus due to larger molecules
  5. Chlorine: lower due to smaller molecules
  6. Argon: lowest, monoatomic
• What type of forces do monoatomic molecules have?

  Weak van der Waals forces between atoms