25 Elements - PowerPoint Presentation

Slide1

25 Elements

By:

Luis MartinezSlide2

#1 Hydrogen

Hydrogen is the lightest element.

It

is by far the most abundant element in the universe and makes up about

90

% of the universe by weight.

Hydrogen

as water (H2O) is absolutely essential to life and it is present in all organic compounds. Hydrogen is the lightest gas

.

Hydrogen gas was used in lighter-than-air balloons for transport but is far too dangerous because of the fire risk (Hindenburg

).Slide3

#2 Helium

Helium is one of the so-called noble gases. Helium gas is an unreactive,

colorless,

and

odorless

monoatomic gas. Helium is available in

pressurized

tanks.

Helium is the second most abundant element in the universe after hydrogen. α-particles are doubly

ionized

helium atoms, He2+.

Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don't try it!).Slide4

#3 Lithium

Lithium

is a solid only about half as dense as water and lithium metal is the least dense metal. A freshly cut chunk of lithium is silvery, but tarnishes in a minute or so in air to give a grey surface.

Its

chemistry is dominated by its tendency to lose an electron to form Li+. It is the first element within the second period.

Lithium is mixed (alloyed) with

Aluminium

and magnesium for light-weight alloys, and is also used in batteries, some greases, some glasses, and in

medicine.Slide5

#4

Beryllium

It is a metal and has a high melting point. At ordinary temperatures, beryllium resists oxidation in air. Beryllium compounds are very toxic. Its ability to scratch glass is probably due to the formation of a thin layer of the oxide

.

Its chemistry is dominated by its tendency to lose an electron to form Be2+. As this ion is so small it is highly

polarizing,

to the extent that its compounds are rather covalent. Its small size means that its complexes tend to be tetrahedral

rather

than octahedral

.Slide6

#5 Boron

O

ron

is a Group 13 element that has properties which are borderline between metals and non-metals (semimetallic). It is a semiconductor rather than a metallic conductor. Chemically it is closer to silicon than to

Aluminium,

gallium, indium, and thallium.

Crystalline boron is inert chemically and is resistant to attack by boiling HF or HCl. When finely divided it is attacked slowly by hot concentrated nitric acid

.Slide7

#6 Carbon

Carbon is a Group 14 element and is distributed very widely in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets.

Carbon is found free in nature in three allotropic forms: amorphous, graphite, and diamond

.

Carbon

, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in ancient volcanic "pipes" such as found in South Africa. Diamonds are also recovered from the ocean floor

off the Cape of Good Hope.Slide8

#7 Nitrogen

Nitrogen

is a Group 15 element.

Nitrogen

makes up about 78% of the atmosphere by volume but the atmosphere of Mars contains less than 3% nitrogen.

The

element seemed so inert that Lavoisier named it azote, meaning "without life". However, its compounds are vital components of foods, fertilizers, and explosives.

Nitrogen

gas is

colorless, odorless,

and generally inert. As a liquid it is also

colorless

and

odorlessSlide9

#8 Oxygen

Oxygen is a Group 16 element

.

While about one fifth of the atmosphere is oxygen gas, the atmosphere of Mars contains only about 0.15% oxygen.

Oxygen

is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle, one process responsible for stellar energy production

.

Oxygen in excited states is responsible for the bright red and yellow-green

colors

of the aurora. About two thirds of the human body, and nine tenths of water, is oxygen.Slide10

#9 Fluorine

Fluorine

is a Group 17 element.

Fluorine

is the most electronegative and reactive of all elements.

It

is a pale yellow, corrosive gas, which reacts with practically all organic and inorganic substances. Finely divided metals, glass, ceramics, carbon, and even water burn in fluorine with a bright flame. Slide11

#10 Neon

Neon is a very inert element. Neon forms an unstable hydrate. In a vacuum discharge tube, neon glows reddish orange

.

Of all the rare gases, the discharge of neon is the most intense at ordinary voltages and currents. It is present in the atmosphere as 1 part in 65000.

Liquid

neon has over 40 times more refrigerating capacity than liquid helium, and more than 3

times that of liquid hydrogen.Slide12

#11 Sodium

Sodium is a Group 1 element (or IA in older

labeling

styles).

Group

1 elements are often referred to as the "alkali metals".

The

chemistry of sodium is dominated by the +1 ion Na+. Sodium salts impart a characteristic orange/yellow

color

to flames and orange street lighting is orange because of the presence of sodium in the lamp.Slide13

#12 Magnesium

Magnesium is a grayish-white, fairly tough metal

.

Magnesium is the eighth most abundant element in the earth's crust although not found in it's elemental form.

It

is a Group 2 element (Group IIA in older

labeling

schemes). Group 2 elements are called alkaline earth metals. Magnesium metal burns with a very bright light.Slide14

#

13

Aluminium

Pure

Aluminium

is a silvery-white metal with many desirable characteristics.

It

is light, nontoxic (as the metal), nonmagnetic and

non sparking

.

It

is somewhat decorative. It is easily formed, machined, and cast

.

Pure

Aluminium

is soft and lacks strength, but alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful

properties.

Slide15

#14 Silicon

Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites.

Silicon

makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen

.

Silicon is important in plant and animal life.Slide16

#15 Phosphorus

Phosphorus is commonly misspelled "phosphorous

".

It is an essential component of living systems and is found in nervous tissue, bones and cell protoplasm. Phosphorus exists in several allotropic forms including white (or yellow), red, and black (or violet

).

White phosphorus has two modifications. Ordinary phosphorus is a waxy white solid. When pure, it is

colorless

and transparent. It is insoluble in water, but soluble in carbon disulphide. Slide17

#16 Sulfur

Sulphur (sulfur) is a pale yellow,

odorless,

brittle solid, which is insoluble in water but soluble in carbon disulphide. Sulphur is essential to life. It is a minor constituent of fats, body fluids, and skeletal minerals.

The spelling of

Sulphur

is "sulfur" in the USA while

Sulphur

is common elsewhere. IUPAC has does not have jurisdiction over language but has decided sulfur is preferred.

Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, Epsom salts, and barite. It is recovered commercially from "salt domes" along the Gulf Coast of the USA.Slide18

#17 Chlorine

Chlorine is a greenish yellow gas which combines directly with nearly all elements. Chlorine is a respiratory irritant.

The

gas irritates the mucous membranes and the liquid burns the skin. As little as 3.5 ppm can be detected as an

odor,

and 1000 ppm is likely to be fatal after a few deep breaths. It was used as a war gas in

1915

It

is not found in a free state in nature, but is found commonly as NaCl (solid or seawater).Slide19

#18 Argon

Argon is a

colorless

and

odorless

gas present to a very small extent in the atmosphere

.

Argon is very inert (indeed it is referred to as one of the noble gases) and is not known to form true chemical compounds.

It

makes a good atmosphere for working with air-sensitive materials since it is heavier than air and less reactive than N2. Today, the chemical symbol for argon is Ar but until 1957 its

symbol

was simply A.Slide20

#19 Potassium

Potassium is a metal and is the seventh most abundant and makes up about 1.5 % by weight of the earth's crust.

Potassium

is an essential constituent for plant growth and it is found in most soils. It is also a vital element in the human diet.

Potassium is never found free in nature, but is obtained by electrolysis of the chloride or hydroxide, much in the same manner as prepared by

Davy.Slide21

#20 Calcium

Calcium as the element is a grey silvery metal. The metal is rather hard

.

Calcium is an essential constituent of leaves, bones, teeth, and shells. Calcium is the fifth most abundant element in the earth's crust and makes up more than 3% of the crust.

Calcium

does not occur as the metal itself in nature and instead is found in various minerals including as limestone, gypsum and fluorite. Slide22

#21 Scandium

Scandium is a silvery-white metal which develops a slightly yellowish or pinkish cast upon exposure to air

.

It is relatively soft, and resembles yttrium and the rare-earth metals more than it resembles

Aluminium

or titanium

.

Scandium reacts rapidly with many acids.Slide23

#22 Titanium

Titanium

s a lustrous, white metal when pure.

Titanium

minerals are quite

common

.The

metal has a low density, good strength, is easily fabricated, and has excellent corrosion resistance.

The

metal burns in air and is the only element that burns in nitrogen. It is

marvelous

in fireworks.Slide24

#23 Vanadium

Pure vanadium is a greyish silvery metal, and is soft and ductile

.

It has good corrosion resistance to alkalis, sulphuric acid, hydrochloric acid, and salt waters

.

The metal oxidizes readily above 660°C to form V2O5.

Industrially

, most vanadium produced is used as an additive to improve steels. Slide25

#24 Chromium

Chromium is steel-gray, lustrous, hard, metallic, and takes a high polish.

Its

compounds are toxic. It is found as chromite ore

.

Siberian red lead (crocoite, PrCrO4) is a chromium ore prized as a red pigment for oil paints.

Similarly

, traces of chromium incorporated into the crystal lattice of corundum (crystalline

Aluminium

oxide, Al2O3) Slide26

#25 ManganeseManganese metal is gray-white, resembling iron, but is harder and very brittle. The metal is reactive chemically, and decomposes cold water slowly. Manganese is widely distributed throughout the animal kingdom.

It is an important trace element and may be essential for utilization of vitamin B. Manganese is present in quantity the floor of oceans. It is an important component of steel.