Week 5 -G2- Content

Question 1

Group 2: Properties and Trends

Answer 1

• These metals are silvery, like group 1.
• Like Group 1, they have low densities (not low
  charge densities!)
• Their density increases down the group, but their
  bond strength does not.
• Atoms of the Group 2 elements are smaller than the
  neighboring Group 1 elements as a consequence of
  the greater nuclear charge of the Group 2 elements.

Question 2

Metling Points of Alkali Earth Metals:

Answer 2

• There is a higher charge density in the ions of group
  2, and this increases the melting points of the pure
  metals drastically over the alkali metals:
• Stronger metallic bonding in the alkaline earth metals
  (than the alkali metals)
• Higher melting points, greater enthalpies of
  atomization, greater hardness than the alkali metals

Question 3

Chemistry of Alkali Earth Metals:

Answer 3

• Good reducing agents. Proportional to atomic number.
• Although not as violently reactive toward water as the alkali
  metals, all the alkaline earths react with acids to generate
  hydrogen.

Question 4

Magnesium’s Special Reactivity:

Answer 4

• The reaction with CO2
  is the reason that Mg fires cannot
  be extinguished using a regular fire extinguisher!
• Mg metal will insert itself in C-X bonds, where X is a
  halogen (mainly Cl and Br). Compounds of this nature are
  called Grignard reagents”

Question 5

Magnesium aluminum alloys:

Answer 5

-Used for casting (as opposed to
forging). This makes them easier to
shape into complex components.

• Increases the material’s
  strength

-don’t
require heat treatment.

Question 6

Diagonal Relationships:

Answer 6

-Charge density helps dictate properties
and reactivities:

• Diagonal relationships (top of the
  periodic table) are based on this idea
• This relationship breaks down elsewhere
  on the periodic table, but you can still
  look at charge density to compare

Question 7

Beryllium

Answer 7

-Used in the windows of X-ray
tubes (air stable and it is the
most transparent material for Xrays.

-Doesn’t react with water, but forms very strong, borderline-covalent bonds with water

• Beryllium can react in both an acid and base environment to produce
  different sp

Question 8

Radium:

Answer 8

• Radioactive!
• Used in the mid 1900s to paint
  the hands and numbers of clocks
  and watches

Question 9

Alkali Earth Ions:

Answer 9

• Always in the +2 oxidation state
• Ionic radii increase down the group (but are smaller
  than alkali metals)
• Form ionic bonds,
• Higher charge density than alkali metals
• Unlike Alkali metals, the salts of alkaline earth metals
  are generally not water soluble

Question 10

Calcium Chloride in Hot Packs:

Answer 10

• This is the basis of hard water and the basics
  of cement and mortar
• Calcium chloride is cheap to produce , exothermic,

Question 11

Biological Aspects of Group II : (Mg and Ca)

Answer 11

• Magnesium is in chlorophyll and is critical
  for photosynthesis
• Mg2+ and Ca2+ are present in body fluids.
  Mg within the cells and calcium outside of
  cells
• Ca2+ critical for blood clotting, muscle
  contractions