Introduction
Gold is the precious transition metal located in group 11 and 6th period of the periodic table. Its atomic number is 79 whereas its atomic mass is 196.96. Gold has 79 electrons. It has 79 protons and 118 neutrons in its nucleus. Its scientific name is “Aurum”. It is represented by the symbol “Au”.
Naming and History
The name is said to be from the Sanskrit word “Jval”. It is also said that it came from the Anglo-Saxon word gold. Although the scientific name of Gold is from the Latin word “Aurum” for gold.
Gold is known to man since prehistoric times. The use of gold is dated back at least 6200 years ago. Egyptians began mining gold by 2000 BC. The gold objects had been found from the royal graves in ancient Ur dated from 3800 to 2000 BC.
Gold found in Egyptian tombs dated at least 5000 years ago. The Egyptians transformed gold into sheets, wires, and foils. They used the word “Nub” for gold and is related to the name of the place Nubia where much of gold was obtained in Egypt.
Alchemists thought gold was made of sulphur and mercury in equal proportions but failed to produce gold. This led to the idea that the substance was not pure enough or perfect proportions of metals had not been achieved.
Occurrence of Gold
Gold mostly occurs in form of nuggets, flakes, or grains. It is unreactive so found in its native form with 8 – 10% silver alloyed in it. The oceans contain gold. On earth, it occurs in igneous rocks. It also occurs in veins and alluvial deposits.
The major suppliers of Gold to the world are China, South Africa, Australia. Other mining sites are present in Canada, Russia, Nevada, and South Dakota.
Properties of Gold
Gold is yellow, noble metal with an excellent sheen. It is highly ductile and malleable. Its one gram can be beaten into one square meter sheet of gold. It is an excellent conductor of heat and electricity.
The term noble is given to is due to the fact that it does not corrode in water and air under normal conditions. When it is finely divided it may occur black, ruby, or purple. It is associated with minerals like quartz, pyrite, etc.
It does not react with reagents and remains unaffected with most of the acids. Aqua regia which is basically one part nitric acid and three parts hydrochloric acid is used to dissolve gold. It does not react with halogens but slowly from aurum chloride on reaction with chlorine.
It is unstable that when heated decomposes to pure metals. The melting point of gold is 1064.18°C and its boiling point is 2856°C. It is the seventh most dense metal with a density of 19.282 grams per cubic centimeter. It exists as solid at room temperature.
Gold in Biological Systems
There is no known significant role of gold in living systems and it is considered to be non-toxic.
Uses of Gold
- The most important use of gold is in jewelry and coinage.
- It was used as a standard of monetary systems and is still used in many places.
- It is alloyed with other metals to increase its strength.
- It is used in embroidery by the gold thread on clothes.
- Satellites are gold-coated because it is an excellent reflector of radiation and is unreactive.
- Small amounts of gold flakes are used in sweets and other foods.
- It is widely used in gold plating.
- Gold is used in circuits and microelectronics.
Isotopes of Gold
There are estimated to be 36 isotopes of gold ranging from mass numbers 170 to 205. The naturally occurring stable isotope is Au- 197.
- Au- 198 is a radioactive isotope used for the treatment of cancers.
MCQs about Gold
- What is the atomic number of gold?
- A) 78
- B) 79
- C) 80
- D) 81
- Answer: B) 79
- Which word is the scientific name for gold?
- A) Gold
- B) Aurum
- C) Jval
- D) Nub
- Answer: B) Aurum
- What is the historical origin of the name “gold”?
- A) Anglo-Saxon
- B) Sanskrit
- C) Latin
- D) Greek
- Answer: B) Sanskrit
- When did Egyptians start mining gold?
- A) 1000 BC
- B) 2000 BC
- C) 3000 BC
- D) 4000 BC
- Answer: B) 2000 BC
- In what form is gold mostly found on Earth?
- A) Compounds
- B) Nuggets, flakes, or grains
- C) Liquid state
- D) Gaseous state
- Answer: B) Nuggets, flakes, or grains
- What is the primary reason gold is considered a noble metal?
- A) Reactivity in water
- B) High ductility
- C) Corrosion resistance in normal conditions
- D) Excellent conductivity
- Answer: C) Corrosion resistance in normal conditions
- Which acid is used to dissolve gold?
- A) Nitric acid
- B) Hydrochloric acid
- C) Sulfuric acid
- D) Aqua regia
- Answer: D) Aqua regia
- What is the melting point of gold?
- A) 500°C
- B) 1000°C
- C) 1500°C
- D) 1064.18°C
- Answer: D) 1064.18°C
- Why are satellites often gold-coated?
- A) Decorative purposes
- B) Excellent conductor of electricity
- C) Excellent reflector of radiation
- D) Increased strength
- Answer: C) Excellent reflector of radiation
- What is the primary use of gold in the field of microelectronics?
- A) Jewelry
- B) Coinage
- C) Gold plating
- D) Embroidery
- Answer: C) Gold plating
- How many isotopes of gold are estimated to exist?
- A) 12
- B) 24
- C) 36
- D) 48
- Answer: C) 36
- Which isotope of gold is used for the treatment of cancers?
- A) Au-197
- B) Au-198
- C) Au-199
- D) Au-200
- Answer: B) Au-198
- What is the density of gold?
- A) 15.678 grams per cubic centimeter
- B) 17.895 grams per cubic centimeter
- C) 19.282 grams per cubic centimeter
- D) 21.456 grams per cubic centimeter
- Answer: C) 19.282 grams per cubic centimeter
- Which metal is often alloyed with gold to increase its strength?
- What is the naturally occurring stable isotope of gold?
- A) Au-196
- B) Au-197
- C) Au-198
- D) Au-199
- Answer: B) Au-197
- What does the term “noble” refer to in the context of gold?
- A) Reactivity
- B) Ductility
- C) Corrosion resistance
- D) Conductivity
- Answer: C) Corrosion resistance
- Which period and group does gold belong to in the periodic table?
- A) 5th period, group 10
- B) 6th period, group 11
- C) 7th period, group 12
- D) 8th period, group 13
- Answer: B) 6th period, group 11
- What is the symbol used to represent gold?
- A) G
- B) Au
- C) Go
- D) Gl
- Answer: B) Au
- According to the text, what is the use of the Latin word “Aurum”?
- A) To describe gold in its native form
- B) To represent gold’s atomic number
- C) As the scientific name for gold
- D) To name gold in jewelry
- Answer: C) As the scientific name for gold
- Which metal is alloyed with gold to create a thread used in embroidery?
- A) Silver
- B) Copper
- C) Platinum
- D) Iron
- Answer: A) Silver
- What was the substance alchemists believed gold was made of in equal proportions?
- A) Iron and sulfur
- B) Silver and mercury
- C) Sulfur and mercury
- D) Copper and gold
- Answer: C) Sulfur and mercury
- What is the primary reason gold is used in circuits and microelectronics?
- A) High melting point
- B) Excellent conductivity
- C) Resistance to corrosion
- D) Alloying properties
- Answer: B) Excellent conductivity
- In what form did the Egyptians transform gold in ancient times?
- A) Liquids
- B) Sheets, wires, and foils
- C) Gaseous state
- D) Compounds
- Answer: B) Sheets, wires, and foils
- Which acid, when combined, forms aqua regia used to dissolve gold?
- A) Nitric acid and sulfuric acid
- B) Hydrochloric acid and sulfuric acid
- C) Nitric acid and hydrochloric acid
- D) Sulfuric acid and hydrofluoric acid
- Answer: C) Nitric acid and hydrochloric acid
- What is the term given to gold when it is finely divided and may appear black, ruby, or purple?
- A) Noble gold
- B) Alchemic gold
- C) Reactive gold
- D) Colloidal gold
- Answer: D) Colloidal gold
- Which country is NOT mentioned as a major supplier of gold to the world?
- A) China
- B) South Africa
- C) Brazil
- D) Australia
- Answer: C) Brazil
Summary:
The tutorial on Gold provides comprehensive insights into the occurrence, properties, uses, and isotopes of this precious transition metal. Beginning with an introduction to its position on the periodic table and its fundamental characteristics, the tutorial delves into the naming and historical aspects of gold, tracing its recognition by various cultures since ancient times.
The occurrence of gold, primarily in nuggets, flakes, or grains, is explored, highlighting its native form with a silver alloy. Major global suppliers are identified, emphasizing its presence in diverse geological formations. The properties of gold, such as its noble nature, ductility, and conductivity, are detailed, along with its reactions to various substances.
The tutorial touches on the limited role of gold in biological systems, emphasizing its non-toxic nature. A significant portion is dedicated to the multifaceted uses of gold, including its prominence in jewelry, coinage, and its utilization in diverse applications such as satellites, embroidery, and microelectronics.
The section on isotopes reveals the existence of 36 isotopes, with a focus on Au-197 as the naturally occurring stable isotope and Au-198 for medical applications in cancer treatment. Overall, the tutorial provides a comprehensive understanding of gold’s characteristics and applications, appealing to those interested in its scientific, historical, and practical aspects.