Chemical Families; Patterns in properties

• Atomic radius decreases across periods due to increasing nuclear charge pulling electrons closer to the nucleus.
• Ionization energy is the amount of energy required to remove an electron from an atom or molecule.
• Elements in the same group have similar physical and chemical properties
• Trends in physical and chemical properties of elements in the same group vary down the group
• Elements in the same group constitute a chemical family
• Group I elements are called Alkali metals, except Hydrogen which is a non-metal
• Alkali metals include: Lithium, Sodium, Potassium, Rubidium, Caesium, Francium
• All alkali metals have one electron in the outer energy level, making them monovalent
• Alkali metals donate/lose the outer electron to have oxidation state M+
• The number of energy levels increases down the group from Lithium to Francium
• Atomic size increases with the number of energy levels, e.g., Potassium has a larger atomic size than Sodium
• Atomic radius is the distance between the nucleus and the outermost energy level, measured in nanometers (n)
• Ionic radius is the distance between the nucleus of an ion and the outermost energy level, also measured in nanometers (n)
• Atomic and ionic radius increase down the group as the number of energy levels increases
• Electropositivity increases as atomic radius increases
• Ionization energy decreases down the group as atomic radius increases
• Alkali metals are soft and easy to cut, with the ease of cutting increasing down the group
• Alkali metals have a shiny grey metallic luster when freshly cut
• Alkali metals have relatively low melting and boiling points compared to common metals like Iron
• Alkali metals are good thermal and electrical conductors
• Alkali metals react with air/oxygen and burn in air/oxygen to form metal oxides
• Alkali metals react with water to form hydroxides and hydrogen gas
• Alkali metals react with chlorine to form metal chlorides
• Some uses of alkali metals include making sodium cyanide, seasoning food, and coolant in nuclear reactors
• Alkaline earth metals include: Beryllium, Magnesium, Calcium, Strontium, Barium, Radium
• All alkaline earth metal atoms have two electrons in the outer energy level
• Alkaline earth metals are divalent and donate/lose the two outer electrons to have oxidation state M 2+
• The number of energy levels increases down the group from Beryllium to Radium
• Atomic radius and ionic radius of alkaline earth metals increase down the group as the number of energy levels increases
• Electropositivity of alkaline earth metals increases with increase in atomic radius/size
• 1st ionization energy decreases down the group for alkaline earth metals as the atomic radius increases
• 2nd ionization energy is always higher than the 1st ionization energy
• Atomic radius of alkali metals is higher than that of alkaline earth metals
• Alkaline earth metals are not soft and easy to cut like alkali metals
• Alkaline earth metals are ductile, malleable, and have high tensile strength
• Alkaline earth metals have a shiny grey metallic luster when freshly polished
• Alkaline earth metals have a relatively high melting/boiling point compared to alkali metals
• Alkaline earth metals are good thermal and electrical conductors
• Observations:

  • Effervescence/fizzing/bubbles with dilute sulphuric(VI) and nitric(V) acids
  • Little effervescence/fizzing/bubbles with calcium and dilute sulphuric(VI) acid
  • Colourless gas produced that extinguishes a burning splint with an explosion/"pop" sound
  • No gas produced with Nitric(V) acid
  • Colourless solution is formed
• Explanation:

  • Dilute acids react with alkaline earth metals to form a salt and produce hydrogen gas
  • Nitric(V) acid is a strong oxidizing agent that quickly oxidizes the hydrogen produced to water
  • Calcium is very reactive with dilute acids, so a very small piece of very dilute acid should be used