Periodic Activity of Metals
Publication No. 12620
Elements are classified based on similarities, differences and trends in their properties, including their chemical reactions. The reactions of alkali and alkaline earth metals with water are pretty spectacular chemical reactions. Mixtures bubble and boil, fizz and hiss and may even smoke and burn. Introduce the study of the periodic table and periodic trends with this exciting demonstration of the activity of metals.
(for each demonstration)
Calcium turnings, Ca, 0.3 g*
Lithium metal, Li, precut piece*
Magnesium ribbon, Mg, 3-cm*
Sodium metal, Na, precut piece*
Phenolphthalein, 1% solution, 2 mL*
Water, distilled or deionized, 600 mL
Beaker, Berzelius (tall-form), Pyrex®, 500-mL, 4
Forceps or tongs
Petri dishes, disposable, 4*
*Materials included in kit.
Lithium and sodium are flammable, water-reactive, corrosive solids; dangerous when exposed to heat or flame. They react violently with water to produce flammable hydrogen gas and solutions of corrosive metal hydroxides. Hydrogen gas may be released in sufficient quantities to cause ignition. Do NOT “scale up” this demonstration using larger pieces of sodium or lithium! These metals are shipped in dry mineral oil. Store them in mineral oil until immediately before use. Do not allow these metals to stand exposed to air from one class period to another or for extended periods of time. Purchasing small, pre-cut pieces of lithium and sodium greatly reduces their potential hazard. Calcium metal is flammable in finely divided form and reacts upon contact with water to give flammable hydrogen gas and corrosive calcium hydroxide. Magnesium metal is a flammable solid and burns with an intense flame. Perform this demonstration in a well-ventilated lab only. Do not handle any of the metals with bare hands. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. All students or spectators should also be wearing chemical splash goggles during this demonstration. Use a Class D powder fire extinguisher such as dry sand for reactive metals. Please review current Safety Data Sheets for safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Use tongs or forceps to remove unreacted magnesium from its beaker. Dispose of excess magnesium metal according to Flinn Suggested Disposal Method #26a. Do not dispose of any of the other reaction mixtures until all of the metal in each has completely reacted. The resulting basic solutions in each beaker can be neutralized and disposed of according to Flinn Suggested Disposal Method #10.
“Sodium is a soft, silver-white solid. Upon exposure to air it gradually develops a white oxide coating. It can be cut with a knife. It is less dense than water and reacts spontaneously and vigorously on contact with water. The metal piece appears to pop or sizzle on the surface and a smoky white gas forms. The metal may ignite on the surface of the water in the vicinity of the smoke. The products are hydrogen gas and sodium hydroxide. The hydrogen gas that is formed ‘pops’ and briefly ignites. Sodium hydroxide makes the solution basic (red) to phenolphthalein indicator.”
Student Worksheet PDF
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesAsking questions and defining problems
Developing and using models
Planning and carrying out investigations
Analyzing and interpreting data
Disciplinary Core IdeasHS-PS1.A: Structure and Properties of Matter
HS-PS1.B: Chemical Reactions
Cause and effect
Systems and system models
Energy and matter
Structure and function
Stability and change
MS-ESS3-1: Construct a scientific explanation based on evidence for how the uneven distributions of Earth’s mineral, energy, and groundwater resources are the result of past and current geoscience processes.
Answers to Questions
(a) Alkali metals (b) Alkaline earth metals
Na > Li > Ca >> Mg
Metal activity increases in the directions the arrows point.
Potassium metal is dangerously reactive with water (and air). It is more reactive than both sodium and calcium. Metal activity increases going down a column in the periodic table.
a. 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
b. Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
Sodium reacts with water to form hydrogen gas and sodium hydroxide, according to the following balanced chemical equation.
2Na(s) + 2H2O(l) → H2(g) + 2NaOH(aq) + Heat
As sodium metal reacts with water, a great deal of heat is generated. The sodium melts and seems to float or bob on the water surface. The oxide coating that may have dulled the metal disappears and sodium’s silvery gray, metallic character is more apparent. The evolution of hydrogen gas is evident in the production of a white smoke, which pops and ignites as it is heated above its flash point. The formation of sodium hydroxide, a strong base, is inferred from the color change observed with phenolphthalein, an acid–base indicator. Phenolphthalein is colorless in neutral or slightly basic solutions (pH <8) and red in more basic solutions (pH >10). Between pH 8 and 10 phenolphthalein appears various shades of pink.
The balanced chemical equations for reactions of other active metals with water are given.
2Li(s) + 2H2O(l) → H2(g) + 2LiOH(aq)
Ca(s) + 2H2O(l) → H2(g) + Ca(OH)2(aq)
Of the four metals tested, sodium is the most active and magnesium is the least active. Magnesium does not react with water under these conditions (it may react slightly in hot water). The order of metal reactivity is Na > Li, Ca >> Mg. Periodic trends in the activity of metals are generally attributed to differences in their ionization energies. The activity of metals increases as the value of their first ionization energy decreases. Within a vertical column (group or family) of elements in the periodic table, ionization energy decreases from top to bottom. As a result, metal activity increases going down a column in the periodic table (K > Na > Li; Ca > Mg). Across a horizontal row (period or series) in the periodic table, ionization energy also increases from left to right. As a result, metal activity decreases from left to right across a row in the periodic table (Na >> Mg; K >> Ca).
This activity was adapted from The Periodic Table, Flinn ChemTopic™ Labs series, Volume 4. Cesa, I., Editor; Flinn Scientific: Batavia, IL (2002).