Trends in chemical reactivity with water

Trends in chemical reactivity with water

Chemical reactivity

Reactivity refers to the likelihood or intensity with which an atom reacts with other substances. Because chemical processes rely on electron transfer/interaction, this is primarily defined by how easily electrons can be removed (ionisation energy) and how urgently they want to take the electrons of other atoms (electronegativity).

Metals a period reactivity decreases as you move from left to right over time.

As you move further to the left and down the periodic table, the higher the reactivity, the easier it is for electrons to be given or taken away.

Nonmetals – Our reactivity increases as we move from left to right. As we move through the group, our response rate decreases. The greater the electronegativity, the more active the electron exchange. The higher the electronegativity, the higher you move up and to the right on the periodic table.

The chemical reaction of water

Water-reactive compounds strongly reduce chemicals that undergo a chemical reaction with water on their own. Alkali metals, which range from sodium to caesium, and alkaline earth metals, which range from magnesium to barium, are two prominent examples.

Some water-reactive chemicals, such as organometallics and sulfuric acid, are also pyrophoric and should be kept dry. Acid-resistant gloves and a face shield are required, and the procedure should be performed in fume hoods.

The reactivity series ranks metals according to how easily they react. Less reactive metals are displaced from their complexes as more reactive metals react with water.

Alkali metals

The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table; they all react quickly, if not explosively, with cold water, displacing hydrogen. The Group 1 metal (M) is oxidised to metal ions, and water is reduced to hydrogen gas (H₂) and the hydroxide ion (OH). As the periodic table progresses, the alkali metals, also known as Group 1 metals, become more reactive.

Alkaline earth metals

Similar to Group 1 metals, alkaline earth metals  (Be, Mg, Ca, Sr, Ba, and Ra) are the second most reactive metals in the periodic table, increasing reactivity as the period increases. Beryllium (Be) is the only alkaline earth metal that, even when heated to red heat, does not react with water or steam. Beryllium also has a tough outer oxide layer that restricts its reactivity at low temperatures. Magnesium has a minor reaction with water, but when it is combined with steam or water vapour, it produces white magnesium oxide and hydrogen gas. Metal hydroxide is formed when a metal reacts with cold water. Metal oxide is formed when a metal, such as magnesium reacts with steam as a result of metal hydroxides breaking when heated. Despite the fact that calcium, strontium, and barium hydroxides are only marginally water-soluble, they produce enough hydroxide ions to make the surrounding environment basic. Hydroxides are formed when metals react with cold water. Oxides are formed when metals react with steam. When a metal reacts with cold water or steam, hydrogen is always produced.

Reactions of metals with water

When a metal reacts with water, it produces metal hydroxide and hydrogen. 

Sodium reacts violently when it comes into contact with water. 

Na + H2O → NaOH + H2

Water reacts quickly with calcium.

Ca + H2O → Ca(OH)2 

Because calcium hydroxide is  only slightly soluble in water, after saturation, solid calcium hydroxide forms and the solution turns milky.

Reactivity of alkali metals with water

Alkali metals from Group 1 of the periodic table include lithium, sodium, potassium, rubidium, cesium, and francium. Alkaline earth metals such as beryllium, magnesium, calcium, strontium, barium, and radium comprise group 2. However, beryllium does not react with water, and francium is far too rare and unstable to be useful in this context. When mixed with water, alkaline earth metals have a lower reactivity than alkali metals.

Lithium – Because lithium is nearly half the density of water, its reaction with water is relatively slow and gentle. It fizzes on the water’s surface, releasing hydrogen and eventually producing a clear lithium hydroxide solution.

Sodium – When sodium metal reacts with water, the resulting heat instantly melts the metal into a grey-silver ball. The hydrogen gas produced during the reaction propels the ball across the water’s surface, leaving a white trail of sodium hydroxide that eventually dissolves into a clear solution. Hydrogen is known to self-ignite and burn with an orange flame. Larger pieces of sodium metal may explode when they come into contact with water.

Potassium – It is a soft, silver-white metal that, when combined with water, produces hydrogen and potassium hydroxide. The heat from this reaction ignites the hydrogen, producing a bright bluish-pink flame. In water, potassium metal, like sodium metal, has the potential to explode.

Rubidium – It is a flammable, soft metal that can self-ignite when exposed to air. It reacts violently in water, producing hydrogen and rubidium hydroxide, which ignites due to the heat of the reaction.

Cesium – It is a silver-gold alkali metal that is liquid at room temperature and has a high reactivity. It burns in the air and explodes in the water, releasing hydrogen and the most powerful base ever discovered, cesium hydroxide.

Magnesium – It can be found in a variety of minerals, including dolomite, asbestos, and soapstone. Magnesium is a powerful element that is both light and strong. Unless the water is extremely hot, magnesium has a weak reaction. It produces hydrogen and magnesium oxide when exposed to steam.

Calcium – It is the fifth most common element in the periodic table and the third most common metal on the planet (after iron and aluminium). Natural materials containing it include limestone, marble, and chalk. When calcium metal is combined with water, it emits hydrogen gas, resulting in a cloudy white calcium hydroxide solution.

Barium – It is a delicate silver-white metal that oxidises quickly in air and is only found in nature when combined with other elements. When it reacts quickly with water, it produces barium hydroxide and hydrogen.

Strontium – It is a silver-white metal that, like barium, oxidises rapidly in the air. When strontium is submerged in water, it sinks and, after a short time, hydrogen bubbles form on the metal’s surface. When strontium reacts with water, strontium hydroxide and hydrogen are formed.

Radium – It is a whitish radioactive metal that forms a black nitride layer in the air when it rapidly combines with nitrogen. Its use has declined as researchers have discovered safer materials to treat cancer and other diseases. Radium decomposes quickly in water, producing radium hydroxide and hydrogen.

Conclusion

Reactivity alludes to the probability or power with which an iota responds with different substances. Since synthetic cycles depend on electron move/communication, this is basically characterised by how effectively electrons can be taken out (ionisation energy) and how critically they need to take the electrons of different iotas (electronegativity).

Metals, a timeframe reactivity diminishes as you move from left to directly over the long haul.