Here, we learn chemistry of alkali metals(group 1 elements) of s block. Occurrence. reactions, physical properties of group 1 elementsare discussed in this tutorial. Usually, group 1 elements of s block are very reactive and exist as compounds. Their only valence is one.
Elements of alkali metals
| Atomic Number | Element Name | Element Symbol |
|---|---|---|
| 3 | Lithium | Li |
| 11 | Sodium | Na |
| 19 | Potassium | K |
| 37 | Rubidium | Rb |
| 55 | Caesium | Cs |
| 87 | Francium | Fr |
In room temperature condition, Hydrogen element exists as H2 gas andrest of others are solid.
Electron Configuration of alkali metals
Those elements have only one electron in their last shell. Commonly, we can show it as1s2 2s22p6.. ns1
Example:
Na - 1s2 2s22p63s1
K - 1s2 2s22p63s23p64s1
Reactions of alkali metals
Alkali metals are very reactive due to existence of only one electron in their last shell. Lot of compounds of these alkalimetal's are soluble in water. Most solids of alkali metal compounds take white colour.
Reactivity of alkali metals change down the group
Observe the reaction of lithium, sodium and potassium reaction with water. You can clearly see a difference of reactions. Potassium reacts vigorously with water and lithium slowly reacts.
When going down the group, atomic radius of metal increases. To have very good reactivity for metals, ease of eliminating electrons should be high (electrons should be removed easily). When atomic radius increases, elimination of last shell electrons gets more easier. So going down the group, reactivity increases.
- Reactivity of sodium is higher than lithium.
- Reactivity of potassium is higher than sodium.
Water and alkali metals reactions
Alkali metals react with water and emit hydrogen and relevant metal hydroxide are given. These metal hydroxides are strong bases anddissolve very well in water.
Reaction of potassium with water is a highly flammable.
2Na + 2H2O = 2NaOH + H2
Solid sodium metal reacts with water to produce aqueous sodium hydroxide and hydrogen gas.
Acids and alkali metals reaction
Alkali metals react with strong acids(HCl , HNO3 , H2SO4) and emit hydrogen gas and produce relevant alkali metal salt.
2Na + 2HCl = 2NaCl + H2
2K + H2SO4 = K2SO4 + H2
Hydrogen and alkali metals reaction
Metal hydrides (H-) are given as products.
2Na + H2 = 2NaH
Those ionic hydrides have H- ions. These ionic hydrides react with compoundswhich can supply H+ ions. Therefore these hydrides behave as strong reducing agents.So they alkali metal hydrides react with water, alcohols,ammonia and alkyne to eliminate hydrogen gas.
Alkali metal hydrides with proton donors
Reactions of air and alkali metals
Liquid Li reacts (burning) with oxygen gas and make lithium oxide.
Sodium, potassium react with Oxygen and make relevant Oxide of metal.
4Na + O2 = 2Na2O
4K + O2 = 2K2O
When sodium, potassium and other alkali metals at below periods is heated in a hot air stream, alkali metal peroxides are formed.
2Na + O2 = Na2O2
2K + O2 = K2O2
Also potassium, rubidium can make super oxides. Alkali metal superoxides are colourful.
Rb + O2 = RbO2
Reaction of water with alkali metal oxides
Above metal oxides can react with water and make metal hydroxides.
Na2O + H2O = 2NaOH
K2O + H2O = 2KOH
Halogen and alkali metals
group IA elements react with halogen and form alkali metalhalides.Sodium chloride, potassium bromide are some examples to alkali metal halides.
2Na + Cl2 = 2NaCl
Nitrogen and alkali metals
Only lithium reacts with nitrogengas and forms lithium nitride (Li3N) which is a red solid.
6Li + N2 = 2Li3N
Li3N reacts with water and and produceammonia gas andlithium hydroxide.
Li3N + 3H2O = 3LiOH + NH3
Sulfur and alkali metals
Sodium reacts sulfur form metal sulfide when heat is supplied.
2Na + S = Na2S
Those sulfides can react with dilute acids.And hydrogen sulfide gas is released.
class="reaction-equations"Na2S + HCl = 2NaCl + H2S
Ammonia and group IA metals
Sodium reacts with ammonia to produce hydrogen gas and NaNH2. In this reaction ammonia behave as an acid.
2Na + NH3 = NaNH2 + H2
Reaction with phosphorus and alkali metals
Sodium reacts with phosphorous in the presence of heat and produce sodium phosphide.
3Na + P = Na3P
Reaction of hydrogen sulfide and group IA metals
Sodium reacts with hydrogen sulfide (H2S) to give metal sulfide and H2 gas. Due to release of hydrogen gas,hydrogen sulfide is an acidic gas.
2Na + H2S = Na2S + H2
Alkali metal halides
The alkali metal halides have high melting points and they are colourless crystalline solids.
Ex: NaCl , KBr
These alkali metal halides are prepared by the reaction of appropriate oxide, hydroxide or carbonate with aqueous hydrohalic acid(HF, HCl, HBr, HI)
Stability of alkali metal halides
Fluorides of alkali metals are most stable while iodides of alkali metals are least stable.
Melting and boiling points of alkali metal halides
Melting and boiling points of alkali metal halides decreases with the increase in atomic mass of the halides as:
F- > Cl- > Br- > I-
As an example, melting point of NaCl is higher than NaBr.
For given halide ion, melting and boiling points of LiX is always less than NaX.
Solubility of alkali metal halides
All alkali metal halide compounds are solublein water exception of LiF. LiF is insoluble in water due to its high lattice energy because of small cation and smallanion size. Other halide ions of lithium are soluble in ethanol, acetone, ethyl acetate. LiCl is soluble in pyridine.CsI has also low solubility due to smaller hydration energy of its two ions.
Salts of oxo acids
Alkali metals are electropositive metals. Therefore they form salts with oxo acids.
What are the oxo acids?
Oxo acids are those in which the acidic proton which is on a hydroxyl group with an oxo group attached to thesame acid. Carbonic acid (H2CO3), sulfuric acid (H2SO4),phosphoric acid (H3PO4) are some examples.
The alkali metals form salts with all oxo acids. These alkali metal oxo salts are generally soluble in water and thermallystable. But Li2CO3 is not stable to heat and decomposes readily. LiHCO3 does notexist as a solid.
Carbonates and bicarbonates of alkali metals
Carbonates of alkali metals are stable to heat (except lithium carbonate). The stability of thosecarbonates are increased down the group.
LiHCO3 does not exist as a solid. Li2CO3 is not stable to heat as otheralkali earth metal carbonates. Lithium carbonate and alkali earth metal carbonates decompose to metaal oxideand carbon dioxide gas when heat is given.
Bicarbonates of alkali metals (except Llithium bicarbonate) decomposes into the carbonates, carbon dioxide and water.
Colours of super oxides of alkali metals
| Alkali metal | Alkali metal super oxide | Colour |
|---|---|---|
| Potassium | KO2 | Orange |
| Potassium | RbO2 | Brown |
| Potassium | KO2 | Dark Orange |
Why LiCl is soluble in organic solvents?
Li+ has very high polarizing power. Therefore LiCl is covalent in nature. Being covalent in nature,it is soluble in organic solvents.
Why potassium is much reactive than sodium?
Both potassium and sodium are alkali metals and form +1 ions. Sodium is located at third period and potassium is located at fourth period in the periodic table. So radius of potassium is higher than sodium. When radius is higher, eliminating an electron is much easy.
So, potassium can eliminate its last shell electron more easily than sodium atom. So potassium reacts so fast than sodium and reactivity of potassium much higher than sodium.
What are the factors of anomalous behavior of lithium?
- Small size of atom and ion
- high ionization enthalpy
- absence of d- orbitals in its valence shell
What are the precipitates formed by alkali metals?
Many compounds of alkali metals are soluble in water. But few of alkali metal compounds are insoluble in water specially some compounds oflithium. Lithium carbonate, lithium fluoride, lithium carbonate, lithium oxalate are sparingly soluble in water. Solubility of sodium bicarbonate is also less than potassium bicarbonate.
Why sodium should kept under kerosene oil?
Due to higher reactivity, we cannot store sodium outside environment (in air) or water. Sodium can react with oxygen, water.
Kerosene is not reactive liquid. So sodium does not react with kerozene. Therefore we can store sodium metal in kerozene oil.
why are alkali metals not found in nature
Alkali metals are very reactive. SO they readily react with water, oxygen which are common constituents in the environment. So we cannotfind alkali metals as pure metals.
Biological importance of sodium and potassium
- Sodium and potassium are most common cations in biological systems.
- Though Na+ and K+ ions are quite similar chemically but surprisingly they differ greatly in their biological activities.
- Their distribution in biological systems is also different. A typical man weighing 70Kg contains about 90g of sodium and 170gof potassium as compared with only 5g of iron and 0.06g of copper.
- The most salient feature is that K+ ions are present in higher concentrations inside the cells than Na+ ions while theirrelative concentrations arereverse outside the cells.
- In other words, K+ ions are concentrated inside the cells while Na+ ions areconcentrated outside the cells.
- Na+ ions are primarily found in blood plasma and in the interstitial fluidwhich surrounds the cells.
- On the other hand, K+ ions are most abundant cations within cell fluids. There isvery considerable variation in the concentration of Na+ and K+ ions found on the opposite sides of cellmembranes. For example, in blood plasma, Na+ ions are present to the extent of 143m .
Written by : Heshan Nipuna
Last Edition : 27/09/2019
Questions
Why do the alkali metals form many precipitates?
Alkali metals >do not form many precipitates like alkali earth metals and d block metals.
When you study solubility of inorganic compounds, you may see, a lot of alkali metals are soluble in water.
Take few examples to explain this.
- Metal hydroxides solubility: All alkali metal hyydroxides are soluble in the water. But from alkaline earth metals, only barium hydroxide is soluble in water. Also all 3d metal hydroxides are precipitates.
Related Topics to s Block Group 1 Elements - Alkali Metals
why are alkali metals good reducing agents?Metal characteristics of periodic table
FAQs
What are the reactions of alkali metals? ›
Alkali metals react with air to form caustic metal oxides. The heavier alkali metals (rubidium and cesium) will spontaneously ignite upon exposure to air at room temperature. Alkali metals react with water to produce heat, hydrogen gas, and the corresponding metal hydroxide.
What is alkali metal reaction equation? ›The alkali metals can also be heated with hydrogen gas to make alkali metal hydrides such as the lithium hydride ( L i H ) or sodium hydride ( N a H ) compounds. The balanced equation 2 N a ( ) + H ( ) 2 N a H ( ) s g s 2 shows how sodium metal can be reacted with hydrogen gas to produce the sodium hydride compound.
Why are alkali metals so reactive simple answer? ›Alkali metals are among the most reactive metals. This is due in part to their larger atomic radii and low ionization energies. They tend to donate their electrons in reactions and have an oxidation state of +1. These metals are characterized by their soft texture and silvery color.
What is an example of reaction of metals with alkali? ›When alkali (base) reacts with metal, it produces salt and hydrogen gas. Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal. Sodium aluminate and hydrogen gas are formed when sodium hydroxide reacts with aluminium metal.
What do alkali metals react with the most? ›Group 1: Alkali Metals
Alkali metals are also known to react violently and explosively with water. This is because enough heat is given off during the exothermic reaction to ignite the H2(g). Figure 1: Reactivity of Lithium (top), sodium (middle) and potassium (bottom) metals and water.
- They are shiny, soft, metals.
- They are very reactive.
- They all have one valence electron in the outermost shell which they seek to lose in order to have a full outer shell. ...
- They are soft enough to be cut with a knife.
Alkali is defined as an ionic or basic salt of an alkaline earth metal or alkali metal. It is a base that can dissolve in water. An alkali or base is known to have a pH more than 7 .
What happens when alkali metals react with bases? ›When a base reacts with a metal, it involves the formation of salt along with the liberation of hydrogen gas.
How do alkali metals react with oxygen equation? ›All the alkali metals react directly with oxygen; lithium and sodium form monoxides, Li2O and Na2O, and the heavier alkali metals form superoxides, MO2.
Why are alkali metals so reactive quizlet? ›The alkali metals, found in group 1 of the periodic table, are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements.
Are all alkali metals highly reactive? ›
All alkali metals are shiny, soft and highly reactive in nature.
What best describes the reactivity of alkali metals? ›Q. What best describes the reactivity of alkali metals? Reactivity increases left to right across a period.
What are 5 examples of alkalis? ›Examples of strong alkalis (lyes) include barium, sodium, ammonium, calcium, lithium, and potassium hydroxides.
What type of reaction is alkali metals with water? ›Mechanistically, dissolving alkali metals in water is a strongly exothermic process in which electrons move from the metal into the aqueous solution where they react to form hydroxide and hydrogen.
Which alkali is more reactive? ›Francium is most reactive element in periodic table.
Which alkali metal is most reactive in order? ›The reactivity of alkali metals increases from the top to the bottom of the group, so lithium (Li) is the least reactive alkali metal and francium (Fr) is the most reactive.
Do alkali metals react with acids? ›Acids and alkali metals reaction
Alkali metals react with strong acids (HCl , HNO3 , H2SO4) and emit hydrogen gas and produce relevant alkali metal salt.
The alkali metals have the high thermal and electrical conductivity, lustre, ductility, and malleability that are characteristic of metals. Each alkali metal atom has a single electron in its outermost shell.
What is special about alkali metals? ›The alkali metals - lithium, sodium, potassium, rubidium, caesium and francium -- are all shiny, soft and highly reactive. They're soft enough to cut with a knife, and freshly cut surfaces tarnish rapidly in the air. They have to be stored under soil, and are never found naturally as free elements.
What are the main uses of alkali metals? ›- Pure sodium has many applications, including use in sodium-vapor lamps which produce very efficient light .
- Potassium has a vital rolel in biological system. KCl used as a fertilizer while KOH is used in the manufacture of soap.
- Caesium is used making photoelectric cells.
What are the 7 alkali metals? ›
Group 1A (or IA) of the periodic table are the alkali metals: hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). These are (except for hydrogen) soft, shiny, low-melting, highly reactive metals, which tarnish when exposed to air.
Which is an alkali metal quizlet? ›Alkali metals are the chemical elements found in Group 1 of the periodic table. The alkali metals include: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (RB), Cesium (Cs), and Francium (Fr).
What is an alkaline solution quizlet? ›An alkaline solution is one that is a pH higher than 7.0. For instance, venous blood, at a pH of 7.3, is an alkaline solution, as is household ammonia at a pH of 12. Amphoteric.
What happens when alkali reacts with acid? ›When acids and alkalis react together, salt and water are formed.
How do alkali metals react with other elements? ›Alkali metals are highly reactive because of their low first ionization energy. They react violently when exposed to oxygen or water and must be stored and handled with caution. The reactivity of group 1 elements increases down the group, with francium being the most reactive.
What happens to the reactivity of alkali metals as you go down? ›The reactivity of group 1 elements increases as you go down the group because: the atoms become larger. the outer electron becomes further from the nucleus. the force of attraction between the nucleus and the outer electron decreases.
What happens when alkali metals react with hydrogen? ›When an alkali metal is reacted with hydrogen then metallic hydride is formed.
When alkali metals are reacted with water then formed gas is *? ›Alkali metals in reaction with water produce energy, hydrogen gas and metal hydroxide. Like, Hydrogen on reaction with water produces hydronium ion H+H2O→H3O+ or Hydrogen on reaction with water produces hydrogen gas and hydroxide ion H+H2O→H2+OH− .
What are the reactions of the first 3 alkali metals with oxygen? ›Potassium (lilac) burns most vigorously followed by sodium (orange-yellow) and then lithium (red), as you might expect. The word and symbol equations for the combustion reactions of the alkali metals are exactly the same as the equations for tarnishing as they are both reactions of the alkali metals with oxygen.
Which alkali metal is more reactive and why? ›The reactivity of alkali metals increases from the top to the bottom of the group, so lithium (Li) is the least reactive alkali metal and francium (Fr) is the most reactive. Because alkali metals are so reactive, they are found in nature only in combination with other elements.
Which of the alkali metal is highly reactive and why? ›
The reactivity of alkali metals increases down the group due to their larger size and low ionization enthalpy. Thus Cs is highly reactive among alkali metals.
Does reactivity increase down the alkali metals? ›As you go down group 1 (the alkali metals) in the periodic table, the elements get more reactive. As you go up group 7 (the halogens), again, the elements become more reactive.
Which alkali metal is least reactive? ›Concept: The alkali metals are soft and silvery. They are also the most reactive metals having the lowest ionization energies. They react readily with water, lithium being the least reactive and potassium the most.
Are alkali metals unreactive? ›Alkali metals are the most reactive metals because their atoms can easily give away the one outer-level electron. Alkaline-earth metals are less reactive than alkali metals are.
Are alkali metals stable? ›Alkali metals have 1 valence electron on their outer shell. They are more stable when they have 8 valence electrons, so they want to lose that valence electron. They do this by bonding with other elements. When they lose their 1 valence electron, they have a full octet and are therefore stable.
What are 5 characteristics of alkali metals? ›- High reactive metals.
- Not found freely in nature.
- Stored in a mineral oil solution.
- Low melting points.
- Low densities (lower than other metals)
- Low electronegativity.
- Low ionization energy.
- React easily with halogens.
- Sodium hydroxide (NaOH) – often called "caustic soda"
- Potassium hydroxide (KOH) – commonly called "caustic potash"
- Lye – generic term for either of two previous salts or their mixture.
- Calcium hydroxide (Ca(OH)2) – saturated solution known as "limewater"
All of the discovered alkali metals occur in nature as their compounds: in order of abundance, sodium is the most abundant, followed by potassium, lithium, rubidium, caesium, and finally francium, which is very rare due to its extremely high radioactivity; francium occurs only in minute traces in nature as an ...
What are 3 common alkalis? ›- Sodium hydroxide.
- Potassium hydroxide.
- Ammonia.
Ans: Alkali metals form alkali (base) in contact with water, and they form metal oxides when water reacts. Alkali metal oxides are also bases and when dissolved in water, they form an alkaline solution.
Do alkali react quickly with water? ›
All the alkali metals react vigorously with cold water. In each reaction, hydrogen gas is given off and the metal hydroxide is produced. The speed and violence of the reaction increases as you go down the group.
Which alkali metal reacts fastest with water? ›Lithium sodium and potassium all react vigorously with water. Alkali metals need to be stored under oil to prevent them reacting with the oxygen and water vapor in the air. The reactivity of the alkali metals increases down the group. Potassium reacts more vigorously than sodium and lithium is the least reactive.
Does alkali metal reactivity with water increase or decrease as we move down the group? ›The reactions with oxygen and water become more vigorous, showing that the alkali metals become more reactive as we move down the group. The reactivity of an alkali metal is determined by how easily these outer shell electrons can be lost from the atom.
Are alkali metals malleable? ›As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The alkali metals are softer than most other metals. Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water.
What are the reactions of alkali metals with oxygen? ›The alkali metals burn vigorously when heated and placed in a gas jar of oxygen. The oxide forms as white smoke. The reactivity of the group 1 elements increases down the group, so their reactions with oxygen get more vigorous.
What are the 3 types of acid metal reactions? ›- Acid + metal → salt + hydrogen.
- For example:
- Hydrochloric acid + magnesium → magnesium chloride + hydrogen.
- Zinc and iron also react with hydrochloric acid.
- Magnesium, zinc and iron also react with sulfuric acid. ...
- sulfuric acid + iron → iron(II) sulfate + hydrogen.
The alkali metals react with the nonmetals in Group VIIA (F2, Cl2, Br2, I2, and At2) to form ionic compounds or salts. Example: Chlorine reacts with sodium metal to produce sodium chloride, table salt. Because they form salts with so many metals, the elements in Group VIIA are known as the halogens.
What are the 3 most important chemical reactions? ›There are three main types of chemical reactions important in human physiology, synthesis (anabolic), decomposition (catabolic) and exchange.
What are the 4 types of chemical reactions? ›- Synthesis reactions.
- Decomposition reactions.
- Single-replacement reactions.
- Double-replacement reactions.
- Combination reaction.
- Decomposition reaction.
- Displacement reaction.
- Double Displacement reaction.
- Precipitation Reaction.
Do alkali metals react with bases? ›
Because of their low positive charge (+1) and relatively large ionic radii, alkali metal cations have only a weak tendency to react with simple Lewis bases to form metal complexes.