Post-Lab: Periodic Trends and the Properties of Elements

Locate the following metals on the periodic table: magnesium, potassium, and sodium. Based on your answers to Questions #4 and 5, rank these metals in order of their expected activity, from most active to least active.

Potassium, Sodium, Magnesium

Litmus paper changes color in acidic (red) and basic (blue) solutions. The word alkaline is a synonym for basic. Why are the two words, "alkaline" and "earth" used to name the Group IIA metals?

Alkaline earth metals turn the litmus paper blue, which depicts that are basic. Alkaline earth metals are usually derived from minerals found naturally in the earth. For example, limestone.

In Part B, which alkaline earth metal formed the most precipitates? The fewest?

Barium (chloride) formed the most precipitate, and magnesium (chloride) formed the least precipitate.

Which group IIA metal, magnesium or calcium, is more active? Cite your evidence.

Calcium is a more active metal compared to magnesium. When reacting calcium with water it started to fix and bubbled with then turned into a steam. After it formed a precipitate and turned opaque in color. When reaction magnesium with water, it had no reaction and also had no reaction with the litmus test.

Rank the three metals tested in Part A from most active to least active.

Calcium, Magnesium, Aluminum

Which period 3 metal, magnesium or aluminum, is more active? Cite your evidence.

Magnesium is more active than aluminum. When reacting magnesium with HCl, it started to slowly fiz after we let it react for some time. Also, instead of looking more like a metal (shiny), it changed to a more white color. The initial temperature of magnesium was 21.9℃, and the final temperature of magnesium was 29.5℃, which clearly indicates that a reaction had occurred.

Using Equation 1 in the Background Section as an example, write a chemical equation for each precipitate-forming reaction that was observed for strontium in Part B. Include the abbreviations (aq) and (s) to show what compound is responsible for the precipitate in each case.

Na2CO3 (aq) + SrCl2 (aq) → 2 NaCl (aq) + SrCO3 (s) Na2SO4 (aq) + SrCl2 (aq) → SrSO4 (s) + 2 NaCl (aq)

Write a general statement describing the periodic trend in metal activity across a group (vertical column) of the periodic table.

The periodic trend in metal activity across a group is as one goes down a group, there is an increase of metal activity. For example, calcium is more active than magnesium.

Write a general statement describing the periodic trend in metal activity within a period (horizontal row) of the periodic table.

The periodic trend in metal activity within a period (horizontal row) of the periodic table is as one goes across (left to right) the period, the less reactive or the less the metal has activity. For example, aluminum has less activity than magnesium.

Write a general statement that describes the periodic trend in the solubility of alkaline earth metal compounds.

The periodic trend in the solubility of alkaline earth metal compounds is that as one goes down a group, it increases in activity. For example, barium has more activity than strontium or calcium.

Use the solubility pattern observed for the known and unknown alkaline earth compounds in Part B to deduce the identity of the unknown alkaline earth metal. Explain your reasoning.

The unknown alkaline earth compound in Part B is strontium chloride (SrCl2) because compared to the other reactions (MgCl2, CaCl2, BaCl2) strontium chloride formed a precipitate with Na2CO3, and Na2SO4 which were the same reactions for the unknown. Therefore, the unknown alkaline earth compound in Part B is strontium chloride (SrCl2).