Question

Periodic Trends in Group II

Objective

In this experiment, the trend in one of the several periodic properties for group II of the Periodic Table will be determined.

Introduction

Elements in the same group of the Periodic Table have similar chemical and physical properties that gradually change as one goes from one element in the group to the next. By observing the trends in properties, the elements can be arranged in the order in which they appear in the Periodic Table. In this experiment we will study the properties of the elements in Group II (2), the alkaline earth metals.

Group 2 – The Alkaline Earth Metals

The alkaline earth elements are in Group 2 of the Periodic Table. In this experiment Be, Mg, Ca, Ba, and Sr will be studied.   All of the alkaline earth metals are M²⁺ cations (Mg²⁺, Ca²⁺, etc.) when they combine with nonmetals in ionic compounds and when they are in aqueous solution. The reactivity of the cations of beryllium, barium, calcium, magnesium, and strontium will be examined. The metal cations will be reacted with water. The information will be used to rank the reactivity of the metal cations.

If a solution containing one of these cations is mixed with a solution containing an anion, the alkaline earth salt will precipitate if the compound containing those two ions is insoluble. The anions used for testing the alkaline earth cations in this experiment is OH

M_(s) + H₂O_(l)   ¾® M(OH)_2(s) + H_2(g)

The solubilities of the compounds of the alkaline earth cations and the anions show a smooth trend consistent with the order of the cations in the Periodic Table. That is, as we go from one end of the alkaline earth family to the other, the solubilities of the hydroxide salts either gradually increase or decrease. By determining the solubility trends in this experiment, the order of the alkaline earths in the Periodic Table will be able to be confirmed.

Pre-Lab Assignment

As preparation for this experiment, do the following:

• Open the prelab folder on Blackboard for this experiment and follow the instructions to prepare for this experiment.
• Watch the video in the folder. Use to fill in the data sheet and answer the questions.

PERIODIC TRENDS IN GROUP II REPORT SHEET Date: Name: Determine the Reactivity of Alkaline Earth Salts Table 1 - Observations of reactivity of Alkaline Earth Salts Metal Describe the reaction with water. Be Mg Ca Sr Ba Order of reactivity from most reactive to least reactive (use > symbol): Is the data consistent with the order of the Group 2 elements on the Periodic Table?

Answer 1

Solution : = 9 Metal Description of the reaction with water: Be Beryllium (Be) metal does not react with cold water due to its small size and high ionization Although, Beryllium reacts with steam at high temperature (tybically 70°c) give white beryllium- ene Oxide and hydrogen gas. - Be Os + H₂ g Be(s) H₂0 (8) (D. Mg utgois #tha (g) Magnesium (Mg) burns in steam to produce white magnesium oxide and hydrogen gas. Mg(s) + H₂O(g) Clean magnesium oibbon has a mild reaction with cold water and after some time H₂ lg bubbles form on its surface and the magnesium ribbon floats to the surfore. The reaction does not lost lorg as magnesium hydroxide boomed is insoluble in water and thus breventa magnesion from further reaction. mg (OH)₂ Mg(s) H2 Ogg H₂ (9) (s (ii) Ca Calcium (Ca) reacts with slowly with cold water. This is in contrast with magnesium (mg), immediately above calcium in the beriodic table, which is virtually un reactive with cold water. The reaction forms calcium hydroxide and hydrogen gas. Cars, +2thoce The reaction is exothermic in nature. Ca(OH), (09) + Hz (g)

(iv) Sr Stronfrum (Sr) reacts with water quicker than calcium and slower than borium (Bo), to form stvortium hy shoxide , Sn (OH),, and hydrogen gas. Srg + 2H₂0 g & Sr (OH)₂ + H₂ LG The strontium metal sinks in water and after a short time bubbles of hydrogen gas stuck to the surface of the metal. Strontium is water insoluble, but it does react with water. (v) Ba with Barium (Ba) reacts readily and vigourously Cold water to form barium hydroxide, Balor, and hydrogen gas (H₂). Ba(s) + 2H₂O ce Bo(OH), H₂ g The reaction is highly exothermic and the hyckoxide is more scluble than that of strontium hydroxide SvOH), and calcium hydroxide Ca (OH), Q2) Order of reactivity from most reactive to least reactive := Ba> or> ca) mg > Be. VO Yes, the data is consistent with the order of the Group-2 elements on the beriodic table.