(Group 18) Are Located in the Far Right of the Periodic Table. These Elements Were

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Group 18: The Noble Gases The Noble Gases (Group 18) are located in the far right of the periodic table. These elements were previously referred to as the inert gases due to their one important chemical property: they are extremely nonreactive due to their filled valence shell. The reason for this is because Noble Gases were set apart and distinguished relatively late compared to other element groups. 1. 1The Electron Configurations for Noble Gases: Group 18 Helium 1s2 Neon [He] 2s2 2p6 Argon [Ne] 3s2 3p6 Krypton [Ar] 3d10 4s2 4p6 Xenon [Kr] 4d10 5s2 5p6 Radon [Xe] 4f14 5d10 6s2 6p6 Trends within Group 18

1st Boiling Melting Atomic Atomic Ionization Density Atomic point point # mass E/kJ mol- (g/dm3) radius/pm (K) (K) 1 He 2 4.003 4.216 0.95 2372.3 0.1786 31 Ne 10 20.18 27.1 24.7 2080.6 0.9002 38 Ar 18 39.948 87.29 83.6 1520.4 1.7818 71 Kr 36 83.3 120.85 115.8 1350.7 3.708 88 Xe 54 131.29 166.1 161.7 1170.4 5.851 108 Rn 86 222.1 211.5 202.2 1037.1 9.97 120 The Atomic and Physical Properties

 Atomic mass, boiling point and atomic radii INCREASE down a group in the periodic table.

 The first ionization energy, DECREASES down a group in the periodic table.

 The noble gases have the largest ionization energies which reflects their chemical inertness.

 As you go down group 18, atomic radius and inter-atomic forces INCREASES

resulting in an INCREASED melting point, boiling point, enthalpy of vaporization and solubility.

 Group 18's INCREASE in density is correlated to the INCREASE in atomic mass.

 Because they are INCREASING in atomic size, the electron clouds of these non polar atoms become increasingly polarized which leads to weak van Der Waals forces among the atoms. Thus, the formation of liquids and solids is more easily attainable for these heavier elements because of their melting and boiling points.

 Because noble gases’ outer shell is full, they are extremely stable, not tending to form chemical bonds and have a low tendency to gain or lose electrons.

 Under standard conditions the members of the noble gas group behave similarly.

 All are monotomic gases under standard conditions.

 Noble gas atoms, like other atoms in other groups, INCREASE steadily in atomic radius from one period to the next due to the INCREASING number of electrons.

 The size of the atom is positively correlated to several properties of noble gases. The ionization potential DECREASES with an INCREASING radius, because the valence electrons in the larger noble gases are further away from the nucleus, so they are not being held as tightly together by the atom.

 The attractive force INCREASES with the size of the atom as a result of an INCREASE in polarizability and thus a DECREASE in ionization potential.

 Overall, noble gases have weak interatomic forces, and therefore very low boiling and melting points compared to other group elements. For covalently-bonded diatomic and polyatomic gases, heat capacity consists of translational,

4 rotational, and vibrational fractions. Since monatomic gases such as noble gases have no bonds, they cannot absorb heat as bond vibrations. Since the center of mass of monatomic gases is at the nucleus of the atom, and the mass of the electrons is negligible compared to the nucleus, the kinetic energy due to rotation is negligible compared to the kinetic energy of translation, unlike in di- or polyatomic molecules where rotation of nuclei around the center of mass of the molecule contributes to the heat capacity. Therefore, the internal energy per mole of a monatomic noble gas equals its translational contribution = (3/2) R T, where R = universal gas constant and T = absolute temperature. For monatomic gases at a given temperature, the average kinetic energy due to translations of the atoms is practically equal regardless of the element. Therefore at a given temperature, the heavier the atom, the more slowly its gas atoms will move. Monatomic gas mean velocity

DECREASES with increasing molecular mass, and given the simplified heat capacity situation, noble gaseous thermal conductivity DECREASES with increasing molecular mass. The Chemical Properties

 They all are odorless, colorless, nonflammable, and monotonic gases that have low chemical reactivity. Electron Configurations

Correction: Xenon

Atomic Number of Element Number Electrons/Shell 2 Helium 2

10 Neon 2,8 18 Argon 2,8,8 36 Krypton 2,8,18,8 54 Xenon 2,8,18,18,8 86 Radon 2,8,18,32,18,8

 Their full valence electron shells make noble gases extremely stable and least likely to form chemical bonds because they have little tendency to gain or lose electrons. Compounds

 However, although noble gases do not tend to react with other elements to form compounds, there are some exceptions! Xe may form compounds with Fluoride and Oxide. Example

XeF2 (Xenon Difluoride)

 Dense white crystalized solid

 Powerful fluorinating agent

 Covalent inorganic fluorides

 Stable xenon compound

 Decomposes on contact with light or water vapor

 Linear structure

 Moister sensitive

 Low vapor pressure



XeF4(Xenon Tetrafluoride)

 Colorless Crystals

 Square planar structure

 Found in 1963



XeF6(Xenon Hexafluoride)

 Strongest fluorinating agent

 Colorless solid

 Highest of the three binary fluorides of xenon (XeF2 and XeF6)  Exergonic and stable at normal temperatures

 Readily sublimes into intense yellow vapors

 Structure lacks perfect octahedral symmetry



XeO4 (Xenon Tetroxide)

 Yellow crystalline solid

 Relatively stable compound of the noble gases

 Oxygen is the only element that can bring xenon up to its highest oxidation state.

 IMPORTANT! Xenon reacts directly ONLY with Fluorine.

The Uses of Noble Gases in Everyday Life Helium

12 is used as a component of breathing gases due to its low solubility in fluids or lipids. For example, gases are absorbed by the blood and body tissues when under pressure during scuba diving. Because of its reduced solubility, little helium is taken into cell membranes, when it replaces part of the breathing mixture, helium causes a decrease in the narcotic effect of the gas at far depths. The reduced amount of dissolved gas in the body means fewer gas bubbles form decreasing the pressure of the ascent. Helium and Argon are used to shield welding arcs and the surrounding base metal from the atmosphere during welding. Helium is used in very low temperature cryogenics, particularly for maintaining superconductors at a very low temperature. Superconductivity is useful for creating very strong magnetic fields. Helium is also the most common carrier gas in gas chromatography. Neon

13 is used for many applications that we see in daily life. For examples: Neon lights, fog lights, TV cine-scopes, lasers, voltage detectors, luminous warnings and also advertising signs. The most popular applications of Neon would be the Neon tubes that we see for advertisement or elaborate decorations. These neon tubes consist with neon and helium or argon under low pressure submitted to electrical discharges. The color of emitted light shown is dependent on the composition of the gaseous mixture and also with the color of the glass of the tube. Pure Neon within a colorless tube can obtain a red light, which reflects a blue shine. These reflected light are also known as fluorescent light.

One of the many colors of neon lights. Argon Argon is used for a diverse group of applications in the growing industries of : electronics, lighting, glass, and metal fabrications. Argon is used in electronics to provide a protective heat transfer medium for ultra-pure semiconductors from silicon crystals and for growing germanium. Argon can also fill fluorescent and incandescent light bulbs; creating the blue light found in neon type lamps.

By utilizing argon's low thermal conductivity, window manufacturers can provide a gas barrier needed to produce double-pane insulated windows. This insulation barrier improves the windows' energy efficiency. Argon also creates an inert gas shield during welding; to flush out melted metals to eliminate porosity in casting; and to provide an oxygen-and-nitrogen free environment for annealing and rolling metals and alloys.

Argon plasma light bulb. Krypton Just like argon, krypton can be found in energy efficient windows. It is also found in fuel sources, lasers and headlights. It is estimated that 30% of energy efficient windows sold in Germany and England are filled with krypton;

17 approximately 1.8 liters of krypton. Being more thermally efficient, krypton is sometimes chosen over argon as a choice for insulation. Krypton can be found in lasers which works as a control for a desired optic wavelength. It is usually mixed with a halogen (most likely fluorine) to produce typically called "excimer" lasers. Krypton is sometimes used within halogen sealed beam headlights. These headlights produces up to double the light output of standard headlights for a brighter gleam. Also, Krypton is used for high performance light bulbs which have higher color temperatures and efficiency because it reduces the rate of evaporation of the filament.

Krypton laser. Xenon Xenon us used for various applications. From incandescent lighting, to development in x-rays, to plasma display panels (PDPs) and much more. Incandescent lighting uses Xenon because less energy can be used to produce the same amount of light output as a normal incandescent lamp. Xenon has also made it possible to obtain better x-rays with reduced amounts of radiation. When mixed with oxygen, it can enhance the contrast in CT imaging. The revolutionize the health care industries. Plasma display panels

(PDPs) using xenon as one of the fill gases may one day replace the large picture tube in television and computer screens. This promises a revolution in the television and computer industries. Nuclear fission products may include a couple of radioactive isotopes of xenon, which also absorb neutrons in nuclear reactor cores. The formation and elimination of radioactive xenon decay products can be a factor in nuclear reactor control. Radon Radon has been said to be the second most frequent cause of lung cancer, after cigarette smoking. However, it can be found in various beneficial applications as well. For examples through: radiotherapy, relief from arthritis, and bathing. In radiotherapy, radon has been used in implantable seeds, made of glass or gold, primarily used to treat cancers. For arthritis, its been said that exposure to radon mitigates auto-

20 immune diseases such as arthritis. Those who have arthritis have actually sought limited exposure to radioactive mine water and radon to relief their pain. However, radon has nevertheless found to induce beneficial long- terms effect. Some places actually have "Radon Spas". For examples: Bad Gastern, Austria and Japanese Onsen in Misasa, Tottori. "Radon Spa" is a relieving therapy where people sit for minutes to hours in a high-radon atmosphere, believing that low doses of radiation will boost up their energy. Applications

Liquid helium is used to cool the superconducting magnets in modern MRI scanners. Noble gases have very low boiling and melting points, which makes them useful as cryogenic refrigerants.[63] In particular, liquid helium, which boils at 4.2 K (−268.95 °C; −452.11 °F), is used for superconducting magnets, such as those needed in nuclear magnetic resonance imaging and nuclear magnetic resonance.[64] Liquid neon, although it does not reach temperatures as low as liquid helium, also finds use in cryogenics because it has over 40 times more refrigerating capacity than liquid helium and over three times more than liquid hydrogen.[61] Helium is used as a component of breathing gases to replace nitrogen, due its low solubility in fluids, especially in lipids. Gases are absorbed by the blood and body tissues when under pressure like in scuba diving, which causes an anesthetic effect known as nitrogen

22 narcosis.[65] Due to its reduced solubility, little helium is taken into cell membranes, and when helium is used to replace part of the breathing mixtures, such as in trimix or heliox, a decrease in the narcotic effect of the gas at depth is obtained.[66] Helium's reduced solubility offers further advantages for the condition known as decompression sickness, or the bends.[11][67] The reduced amount of dissolved gas in the body means that fewer gas bubbles form during the decrease in pressure of the ascent. Another noble gas, argon, is considered the best option for use as a drysuit inflation gas for scuba diving.[68] Helium is also used as filling gas in nuclear fuel rods for nuclear reactors.[69]

Goodyear Blimp

Since the Hindenburg disaster in 1937,[70] helium has replaced hydrogen as a lifting gas in blimps and balloons due to its lightness and incombustibility, despite an 8.6%[71] decrease in buoyancy.[11] In many applications, the noble gases are used to provide an inert atmosphere. Argon is used in the synthesis of air-sensitive compounds that are sensitive to nitrogen. Solid argon is also used for the study of very unstable compounds, such as reactive intermediates, by trapping them in an inert matrix at very low temperatures.[72] Helium is used as the carrier medium in gas chromatography, as a filler gas for thermometers, and in devices for measuring radiation, such as the Geiger counter and the bubble chamber.[62] Helium and argon are both commonly used to shield welding arcs and the surrounding base metal from the atmosphere during welding and cutting, as well as in other metallurgical processes and in the production of silicon for the semiconductor industry.[61]

15,000-watt xenon short-arc lamp used in IMAX projectors Noble gases are commonly used in lighting because of their lack of chemical reactivity. Argon, mixed with nitrogen, is used as a filler gas for incandescent light bulbs.[61] Krypton is used in high-performance light bulbs, which have higher color temperatures and greater efficiency, because it reduces the rate of evaporation of the filament more than argon; halogen lamps, in particular, use krypton mixed with small amounts of compounds of iodine or bromine.[61] The noble gases glow in distinctive colors when used inside gas-discharge lamps, such as "neon lights". These lights are called after neon but often contain other gases and

25 phosphors, which add various hues to the orange-red color of neon. Xenon is commonly used in xenon arc lamps which, due to their nearly continuous spectrum that resembles daylight, find application in film projectors and as automobile headlamps.[61] The noble gases are used in excimer lasers, which are based on short-lived electronically excited molecules known as excimers. The excimers used for lasers may be noble gas dimers such as Ar2, Kr2 or Xe2, or more commonly, the noble gas is combined with a halogen in excimers such as ArF, KrF, XeF, or XeCl. These lasers produce ultraviolet light which, due to its short wavelength (193 nm for ArF and 248 nm for KrF), allows for high- precision imaging. Excimer lasers have many industrial, medical, and scientific applications. They are used for microlithography and microfabrication, which are essential for integrated circuit manufacture, and for laser

26 surgery, including laser angioplasty and eye surgery.[73] Some noble gases have direct application in medicine. Helium is sometimes used to improve the ease of breathing of asthma sufferers.[61] Xenon is used as an anesthetic because of its high solubility in lipids, which makes it more potent than the usual nitrous oxide, and because it is readily eliminated from the body, resulting in faster recovery.[74] Xenon finds application in medical imaging of the lungs through hyperpolarized MRI.[75] Radon, which is highly radioactive and is only available in minute amounts, is used in radiotherapy.[11] Discharge color Colors and spectra (bottom row) of electric discharge in noble gases; only the second row represents pure gases.

Argon (with some Hg

Helium Neon Krypton Xenon in the "Ar" image)

The color of gas discharge emission depends on several factors, including the following:[76]

 discharge parameters (local value of current density and electric field, temperature, etc. – note the color variation along the discharge in the top row);

 gas purity (even small fraction of certain gases can affect color);

 material of the discharge tube envelope – note suppression of the UV and blue components in the bottom-row tubes made of thick household glass.