kimia unsur golongan 6 A

1. By:
1. Dewi Shinta (13630002)
2. Susanti Anugrah R (13630004)
3. Sinta Ayunda (13630012)
4. Muhamad Yorda (13630016)
5. Muhammad Ansori (13630019)
6. Khurrotul Ainia (13630022)
7. A Fiqri Amrullah (13630026)
8. Khoirul Anwar (13630029)
9. Faizatul Hazanah (13630031)

2. WHAT WILL WE
LEARN?

4. SELENIUM (Se)
HISTORY
JONS JAKOB BERZILIUS
Selenium was discovered by Jöns Jacob
Berzelius at Stockholm in 1817. He had
shares in a sulfuric acid works and he was
intrigued by a red-brown sediment which
collected at the bottom of the chambers in
which the acid was made. At first he thought
it was the element tellurium because it gave
off a strong smell of radishes when heated,
but he eventually realised that it was in fact a
new element. He also noted that it was like
sulfur and indeed had properties
intermediate between sulfur and tellurium.
Berzelius found that selenium was present in
samples of tellurium and gave that element
its characteristic smell.
Group 4

5. SELENIUM (Se)
PROPERTIESatomic volume 16,5 Cm3/mol
Oxidation number -2,4,6
Boiling point 685°C, 1265°F, 958 K
Melting point 220.8°C, 429.4°F, 494 K
heat capacity 0,32 Jg-1K-1
covalent radius 1,16 Å
crystal structure hexagonal
State at 20°C Solid
Density (g cm−3) 4.809
Key isotopes 80Se
electrical conductivity 8 x 106 ohm-1cm-1
electronegativity 2,55
formation enthalpy 5,54 kJ/mol
thermal conductivity 2,04 Wm-1k-1
ionization potential 9,752 V
Group 4

6. SELENIUM (Se)
Chemical reaction
Reaction of selenium with air
Selenium burns in air to form the solid
dioxide selenium(IV) oxide, SeO2.
Se8(s) + 8O2(g) → 8SeO2(s)
Reaction of selenium with the halogens
Selenium reacts with fluorine, F2, and burns to form the
hexafluoride selenium(VI) fluoride.
Se8(s) + 24F2(g) → 8SeF6(l) [orange]
Group 4

7. SELENIUM (Se)
Chemical reaction
Group 4
Reaction of selenium with acids
Selenites acids can also be made directly
by the reaction of selenium with nitric
acid. Reaction:
3Se + 4HNO3 → 3H2SeO3 + 4 NO
Reaction of selenium with metal(Selenida)
3Se + 2 Al → Al2Se3
Al2Se3 + 6H2O → 2Al(OH)3
Se + Fe → SeFe

8. Selenium exists in several allotropes (black, red, and gray (not
pictured) allotropes) that interconvert upon heating and
cooling carried out at different temperatures and rates. As
prepared in chemical reactions, selenium is usually an
amorphous, brick-red powder. When rapidly melted, it forms
the black, vitreous form, which is usually sold industrially as
beads. The structure of black selenium is irregular and
complex and consists of polymeric rings with up to 1000
atoms per ring. Black Se is a brittle, lustrous solid that is
slightly soluble in CS2. Upon heating, it softens at 50 °C and
converts to gray selenium at 180 °C.
SELENIUM (Se)
allotropes
Group 4
Black Se
Red Se

9. SELENIUM (Se)
Selenium is found in several rare minerals such as
kruksit and klausthalit. Se also obtained from flue dust
produced during the roasting sulphide ores such as PbS,
CuS, or FeS. The dust is trapped by means of an
electrostatic precipitator. Selenium also occur in the
native form together with S . Most of the world’s
selenium is obtained from the anode muds produced
during the electrolytic refining of copper. These muds
are either roasted with sodium carbonate or sulfuric
acid, or smelted with sodium carbonate to release the
selenium.
HOW TO OBTAIN!!
Group 4

10. SELENIUM (Se)
ADVANTAGE
Group 4
additive to glass
reduce the transmission of
sunlight in architectural glass
make pigments for ceramics, paint
and plastics
useful in photocellssolar cells and
photocopiers.
convert AC electricity to DC
electricity, so is extensively used in
rectifiers.

11. SELENIUM (Se)
DISADVANTAGE
Group 4
The Impact of Selenium Deficiency for the
Body the symptoms arising from selenium
deficiency, can be explained by the decrease
in antioxidants in heart, liver and muscles,
resulting in tissue death and organ failure.
Excess of selenium can cause very harmful
effects that can result from consuming
additional selenium overdose
• queasiness and retch
• hair and nail loss
• neurological damage

13. TELLURIUM (Te)
HISTORY
Group 4
Joseph Müller Von Reichenstein
Tellurium was discovered
in the Habsburg Empire, in
1782 by Franz-Joseph
Müller von Reichenstein in
a mineral containing
tellurium and gold. Martin
Heinrich Klaproth named
the new element in 1798
after the Latin word for
"earth", tellus.

14. TELLURIUM (Te) Group 4
PROPERTIES
atomic volume 20,5 Cm3/mol
Oxidation number 6, 4, 2, −2 ​
Boiling point 1261 K ​(988 °C, ​1810 °F)
Melting point 722.66 K ​(449.51 °C, ​841.12 °F)
heat capacity 25.73 J/(mol·K)
covalent radius 138±4 pm
crystal structure Hexagonal
Density (g cm−3) 6.24 g/cm3
Key isotopes
120, 122, 123, 124, 125, 126, 128,
130
electronegativity Pauling scale: 2.1
Energi of ionization 901,01 KJ/mol

15. Chemical reaction
TELLURIUM (Te) Group 4
Tellurides
Reduction of Te metal produces the tellurides
and polytellurides
ZnTe + 2 HCl → ZnCl2 + H2Te
H2Te is unstable, whereas salts of its conjugate
base [TeH]− are stable.
Halides
The +2 oxidation state is exhibited by the dihalides
Te + X2 + 2 X−→ TeX2
-4
where X is Cl, Br, or I

16. Reaction of tellurium with air
Tellurium burns in air to form the solid
dioxide tellurium(IV) oxide, TeO2.
Te(s) + O2(g) TeO2(s)
Chemical reaction
TELLURIUM (Te) Group 4
Reaction with water (H2O)
Tellurium dioxide reacts with water to form acid tellurous
(H2TeO3).
TeO2 + H2O → H2TeO3

17. ALLOTROPES
TELLURIUM (Te) Group 4
Tellurium has two allotropes, crystalline and amorphous. When
crystalline, tellurium is silvery-white and when it is in pure state it has
a metallic luster. It is a brittle and easily pulverized metalloid.
Amorphous tellurium is a black-brown powder prepared by
precipitating it from a solution of tellurous or telluric acid
(Te(OH)6).Tellurium is a semiconductor that shows a greater electrical
conductivity in certain directions which depends on atomic alignment;
the conductivity increases slightly when exposed to light
(photoconductivity). When in its molten state, tellurium is corrosive to
copper, iron and stainless steel. Of the chalcogens, tellurium has the
highest melting and boiling points, at 722.66 K (841.12 °F) and 1,261 K
(1,810 °F), respectively.

18. TELLURIUM (Te)
The principal source of tellurium is from anode sludges produced during
the electrolytic refining of blister copper.The metal ions are reduced to the
metals, while the telluride is converted to sodium tellurite.
M2Te + O2 + Na2CO3 → Na2TeO3 + 2 M + CO2
Tellurites can be leached from the mixture with water and are normally
present as hydrotellurites HTeO3
− in solutionThe hydrotellurites are
converted into the insoluble tellurium dioxide while the selenites stay in
solution.
HTeO−3 + OH− + H2SO4 → TeO2 + SO2
−4 + 2 H2O
The reduction to the metal is done either by electrolysis or by reacting the
tellurium dioxide with sulfur dioxide in sulfuric acid.[29]
TeO2 + 2 SO2 + 2H2O → Te + 2 SO2
−4 + 4 H+
HOW TO OBTAIN!!
Group 4

19. ADVANTAGE
Group 4TELLURIUM (Te)
The largest consumer of tellurium is metallurgy,
where it is used in iron, copper and lead alloys
Tellurium is used in cadmium telluride (CdTe)
solar panels.
Used to color ceramics
Tellurite agar is used to identify members of the
corynebacterium genus
The strong increase in optical refraction upon
the addition of selenides and tellurides into glass is
used in the production of glass fibers for
telecommunications
Mixtures of selenium and tellurium are used
with barium peroxide as oxidizer in the delay
powder of electric blasting caps

20. DISADVANTAGE
Group 4TELLURIUM (Te)
Tellurium and tellurium compounds are considered to be mildly toxic and
need to be handled with care, although acute poisoning is rare.[6Tellurium
poisoning is particularly difficult to treat as many chelation agents used in
the treatment of metal toxicities will increase the toxicity of tellurium.
Tellurium is not reported to be carcinogenic.
Humans exposed to as little as 0.01 mg/m3 or less in air exude a foul
garlic-like odor known as "tellurium breath."[ This is caused from the
tellurium being metabolized by the body, converting it from any oxidation
state to dimethyl telluride, (CH3)2Te. This is a volatile compound with a
highly pungent garlic-like smell. Even though the metabolic pathways of
tellurium are not known, it is generally assumed that they resemble those
of the more extensively studied selenium, because the final methylated
metabolic products of the two elements are similar.

22. POLONIUM (Po)
HISTORY
Group 4
MARIE AND PIERRE
CURIE
lso tentatively called "radium F", polonium
was discovered by Marie and Pierre Curie in
1898, and was named after Marie Curie's
native land of Poland (Latin: Polonia). Poland
at the time was under Russian, German, and
Austro-Hungarian partition, and did not exist
as an independent country. It was Curie's
hope that naming the element after her
native land would publicize its lack of
independence. Polonium may be the first
element named to highlight a political
controversy

23. POLONIUM (Po) Group 4
PROPERTIES
atomic volume 22.70 cm3/mol
Oxidation number +4, +2and+6
Boiling point 963,03 °C
Melting point 527 K: 254 °C
heat capacity 20 W/mK
Atomic radius
empirical: 168 pm
crystal structure monoclinic
Density (g cm−3) 9.3 g/cm3
Key isotopes 210Po, 214Po, and 218Po
electronegativity 2.0
ionization potential 8.42volts

24. POLONIUM (Po) Group 4
Chemical reaction
ReactiontoAir
Polonium burned in the air and produce
polonium(IV) dioxide
Po(s) +O2(g) PoO2(s)
Reactions withHalogen
In certain circum stances, polonium would react
with chlorine, bromine and iodineto form
tetrahalides.
Po(s) + 2Cl2(g) PoCl4(s)
Po(s) + 2Br2(g) PoBr4(s)
Po(s) + 2I2(g) PoI4(s)

25. Polonium is a radioactive element that exists in two metallic allotropes.
The alpha form is the only known example of a simple cubic crystal
structure in a single atom basis, with an edge length of 335.2 picometers;
the beta form is rhombohedra. The structure of polonium has been
characterized by X-ray diffraction and electron diffraction.
POLONIUM (Po) Group 4
ALLOTROPES
α-Po simple cubic
β –Po rhombohedra

26. POLONIUM (Po) Group 4
HOW TO OBTAIN!!
Polonium is a very rare element in nature because of the short half-life of
all its isotopes. 210Po, 214Po, and 218Po appear in the decay chain of
238U; thus polonium can be found in uranium ores at about 0.1 mg per
metric ton (1 part in 1010), which is approximately 0.2% of the abundance
of radium. The amounts in the Earth's crust are not harmful. Polonium has
been found in tobacco smoke from tobacco leaves grown with phosphate
fertilizers.Because it is present in such small concentrations, isolation of
polonium from natural sources is a very tedious process. The largest batch
of the element ever extracted, performed in the first half of the 20th
century, contained only 40 Ci (1.5 TBq) (9 mg) of polonium-210 and was
obtained by processing 37 tonnes of residues from radium production.[48]
Polonium is now obtained by irradiating bismuth with high-energy
neutrons or protons.

27. ADVANTAGE
POLONIUM (Po) Group 4
Polonium Is used in nuclear testing with the
release element beryllium neutron crate
when shot alpha particles. In Printing and
photography tools, polonium used in tools
that ionize the air to eliminate electrostatic
current collection

28. DISADVANTAGE
POLONIUM (Po) Group 4
Polonium is highly dangerous and has no biological role.[17] By
mass, polonium-210 is around 250,000 times more toxic than
hydrogen cyanide (the LD50 for 210Po is less than 1 microgram
for an average adult (see below) compared with about 250
milligrams for hydrogen cyanide[66]). The main hazard is its
intense radioactivity (as an alpha emitter), which makes it very
difficult to handle safely. Even in microgram amounts, handling
210Po is extremely dangerous, requiring specialized equipment (a
negative pressure alpha glove box equipped with high
performance filters), adequate monitoring, and strict handling
procedures to avoid any contamination.

29. IT IS JUST

30. UNUHEXIUM (Uuh)or
LIVERMORIUM (Lv)
Group 4
HISTORY
Joint Institute for Nuclear Research and
Lawrence Livermore National Laboratory
Livermorium was first synthesized on
July 19, 2000, when scientists at
Dubna (JINR) bombarded a curium-
248 target with accelerated calcium-
48 ions. A single atom was detected,
decaying by alpha emission with
decay energy 10.54 MeV to an
isotope of flerovium. The results
were published in December 2000.
248Cm96 + 48Ca20 → 296 Lv*116 →
293Lv116 +3 1n0 → 289Fl114 + α

31. UNUHEXIUM (Uuh)or
LIVERMORIUM (Lv)
Group 4
PROPERTIES
Phase solid (predicted)
Melting point
637–780 K ​(364–507 °C, ​687–
944 °F) (extrapolated)
Boiling point
1035–1135 K ​(762–
862 °C, ​1403–1583 °F)
(extrapolated)
Density near r.t. 12.9 g/cm3 (predicted)
Heat of fusion 7.61 kJ/mol (extrapolated)
Heat of vaporization 42 kJ/mol (predicted)
Oxidation states −2, +2, +4 ​(predicted)
Ionization energies
1st: 723.6 kJ/mol (predicted)[
2nd: 1331.5 kJ/mol (predicted)
3rd: 2846.3 kJ/mol (predicted)
Atomic radius empirical: 183 pm (predicted)
Covalent radius 162–166 pm (extrapolated)
iso half-life
293Lv 61 ms
292Lv 18 ms
291Lv 18 ms
290Lv 7.1 ms

32. SUMMARY Group 4
PROPERTIES
NATURE periodicity O S Se Te Po Lv
Atomic number 8 16 34 52 84 116
Element categoty nonmetal
lic
nonmetall
ic
nonmetalli
c
metalloid
s
metalloid
s
metal
(probably)
Phase (25°c) Gases solid solid solid solid Predicted
solid
Density (g/cm3) at
20 °c
0,001429 2,07 4,79 6,24 9,4 12.9 (pred
icted)
Melting point (°c) -218,4 115,21 217 449,5 254 364–507
(extrapolat
ed)
Boiling point (°c) -182,7 444,6 684 989,9 962 762–
862 (extra
polated)
elektronegetivitas 3,44 2,58 2,55 2,1 2,0 unknow