Properties of barium

Bar­i­um is an el­e­ment of the sec­ond group of the 6ᵗʰ pe­ri­od of the pe­ri­od­ic ta­ble. It is an al­ka­line earth met­al. In na­ture it is pri­mar­i­ly en­coun­tered in the form of min­er­als – the most im­por­tant of nat­u­ral com­pounds of bar­i­um are barite, Ba­SO₄ and witherite Ba­CO₃. Bar­i­um alu­mosil­i­cates, ni­trates etc. are much more rarely en­coun­tered.

In na­ture it is en­coun­tered in the form of sev­en sta­ble iso­topes (sub­stances with an iden­ti­cal atom­ic num­ber, but dif­fer­ent mass num­bers) with the mass num­bers 132, 134, 135, 136, 137, 138 (the last is the most com­mon). The most abun­dant ra­dioac­tive iso­tope of bar­i­um has a mass num­ber of 130 (the ra­dioac­tiv­i­ty of the iso­tope is low).

Phys­i­cal prop­er­ties

By its ap­pear­ance, bar­i­um, like all met­als of its sub­group, is a soft sil­very-white mal­leable met­al. It has high con­duc­tiv­i­ty and chem­i­cal re­ac­tiv­i­ty.

Ow­ing to its re­ac­tiv­i­ty, bar­i­um is not stored in air – the met­al is cov­ered with a lay­er of kerosene or paraf­fin.

Ob­tain­ing bar­i­um

The pure met­al with­out im­pu­ri­ties can be ob­tained by elec­trol­y­sis of a flux of salt – for ex­am­ple bar­i­um chlo­ride:

К(-): Ba²⁺ + 2е = Ba⁰;

A(+): 2Сl⁻ - 2е = Сl₂;

BaСl₂ = Ва + Cl₂.

Bar­i­um can also be ob­tained by the alu­minother­mic method, re­duc­ing it from the ox­ide with metal­lic alu­minum:

3BaO + 2Al = 3Ba + Al₂O₃ (the re­ac­tion takes place in a vac­u­um at a tem­per­a­ture of 1200-1250 ᵒC or 2192-2282 ᵒF).

Bar­i­um ox­ide is ob­tained for con­duct­ing this re­ac­tion from the barite con­cen­trate of the min­er­al Ba­SO₄ by the fol­low­ing re­ac­tions (all re­ac­tions take place with heat­ing):

1. Ba­SO₄ + 4C = BaS + 4CO;

2. BaS + 2H₂O = Ba(OH)₂ + H₂S (with heat­ing, the hy­drol­y­sis of salt takes place more in­ten­sive­ly);

3. Ba(OH)₂ = BaO + H₂O (heat­ing at 800 ᵒC (1472 ᵒF) makes it pos­si­ble to break down bar­i­um hy­drox­ide Ba(OH)₂ to bar­i­um ox­ide BaO and wa­ter).

In the last re­ac­tion, in the flow of air not only the main ox­ide BaO can be ob­tained, but also bar­i­um per­ox­ide BaO₂.

Chem­i­cal prop­er­ties of bar­i­um

Bar­i­um is no less re­ac­tive than al­ka­line met­als such as sodi­um or potas­si­um. When heat­ed in air, the met­al may ig­nite, and on con­tact with oxy­gen, it may ox­i­dize to bar­i­um ox­ide BaO (in air bar­i­um ni­tride Ba₃N₂ may also form).

Bar­i­um re­acts en­er­get­i­cal­ly with wa­ter with the for­ma­tion of a base (bar­i­um hy­drox­ide) and hy­dro­gen:

Ba + 2H₂O = Ba(OH)₂ + H₂.

With non-met­als, the met­al re­acts with the for­ma­tion of salts:

• Ba + H₂ = BaH₂ (with heat­ing bar­i­um hy­dride forms);

• Ba + S = BaS (bar­i­um sul­fide is formed from sim­ple sub­stances with heat­ing);

• Ba + Br₂ = BaBr₂ (the met­al re­acts with any halo­gens with the for­ma­tion of halo­genides – in this case bar­i­um bro­mide forms);

• 3Ba + 2P = Ba₃P₂ (with heat­ing with phos­pho­rus, bar­i­um phos­phide forms).

Bar­i­um re­acts en­er­get­i­cal­ly with di­lut­ed acids, and with heat­ing also with am­mo­nia:

• Ba + 2HCl = Ba­Cl₂ + H₂;

• 6Ba + 2NH₃ = 3BaH₂ + Ba₃N₂ (bar­i­um hy­dride and ni­tride form).

Click here for the ex­per­i­ment where am­mo­nia foun­tain forms.

When it re­acts with ni­tric acid of dif­fer­ent con­cen­tra­tions, bar­i­um ni­trate and var­i­ous oth­er prod­ucts of re­ac­tion form:

• 4Ba + 10H­NO₃ = 4Ba(NO₃)₂ + NH₄NO₃ + 3H₂O (if the acid is heav­i­ly di­lut­ed);

• 4Ba + 10H­NO₃ = 4Ba(NO₃)₂ + N₂O + 5H₂O (if the con­cen­tra­tion of acid is high).

If the acid is of medi­um con­cen­tra­tion, be­sides bar­i­um ni­trate and wa­ter, molec­u­lar ni­tro­gen may be re­leased.

Bar­i­um ox­ide and hy­drox­ide (BaO, Ba(OH)₂) have typ­i­cal base prop­er­ties – for ex­am­ple they re­act with acids and acidic ox­ides:

• BaO + CO₂ = Ba­CO₃;

• Ba(OH)₂ + CO₂ = Ba­CO₃ + H₂O;

• BaO + 2HCl = Ba­Cl₂ + H₂O;

• Ba(OH)₂ + 2HCl = Ba­Cl₂ + 2H₂O.

When bar­i­um hy­drox­ide is heat­ed up to 800 ᵒC (or 1472 ᵒF), it breaks down to ox­ide and wa­ter, while bar­i­um ox­ide is ca­pa­ble of re­act­ing with wa­ter with the for­ma­tion of hy­drox­ide:

• Ba(OH)₂ = BaO + H₂O;

• BaO + H₂O = Ba(OH)₂.

Qual­i­ta­tive re­ac­tions for the bar­i­um ion

Bar­i­um can be dis­tin­guished from oth­er met­als with sim­i­lar phys­i­cal and chem­i­cal prop­er­ties by the col­or of the flame and the re­ac­tion with sul­fate ions (Ba²⁺ + SO₄²⁻ = Ba­SO₄).

Bar­i­um salt changes col­or in a flame – it be­comes yel­lowy-green. This takes place be­cause of the bar­i­um ions present in the qual­i­ta­tive com­po­si­tion of the salt.

Flame col­ors: the in­flu­ence of dif­fer­ent ions on the col­or of flame (which in­cludes bar­i­um ions)

The pres­ence of bar­i­um ions in a salt can also be de­tect­ed by an ex­change re­ac­tion – for ex­am­ple bar­i­um chlo­ride with sodi­um sul­fate:

Ba­Cl₂ + Na₂­SO₄ = BaSО₄ + NaCl (the re­ac­tion takes place as among the prod­ucts of re­ac­tion is the sed­i­ment Ba­SO₄). Bar­i­um sul­fate is a white milky sed­i­ment which does not dis­solve in acids.

Also from neu­tral bar­i­um salts (for ex­am­ple Ba­Cl₂), in the re­ac­tion in sodi­um rh­odi­zonate Na₂C₆O₆, bar­i­um rh­odi­zonate BaC₆O₆ of a red­dish-brown col­or forms. The re­ac­tion is quite sen­si­tive and makes it pos­si­ble to de­tect bar­i­um ions in small con­cen­tra­tions.

Bar­i­um salts have found wide ap­pli­ca­tion in in­dus­try – elec­tri­cal parts are made from bar­i­um ti­tanate Ba­TiO₃, and bar­i­um sul­fate Ba­SO₄ is used in medicine for di­ag­nos­ing gas­troin­testi­nal dis­eases.