THE PERIODIC TABLE Chapter 15

MENDELEEV 1869

 The first version of the periodic table was published by Dmitri Mendeleev, a Russian chemist

 He arranged the elements in order of increasing atomic mass

 This arrangement created a pattern: elements with similar properties fell

into groups on the table

MENDELEEV

MORE MENDELEEV

 Mendeleev had to leave gaps for elements that had not yet been discovered

 Due to the groupings in his table, he could predict the properties of those missing elements

 Within 15 years, other scientists had discovered the missing elements

MOSELEY  Henry Moseley, an English physicist, improved Mendeleev’s Table

 He arranged the elements by atomic number (increasing number of protons in the nucleus) rather than atomic mass

 This made it very clear how many elements were still undiscovered

TODAY’S PERIODIC TABLE

The elements are still organized by increasing atomic number

The rows (called periods) are labeled 1-7

Period- a row of elements in the periodic table whose properties change gradually and predictably

The columns (called groups) are labeled 1-18

Group- contains elements that have similar physical or chemical properties

ZONES OF THE PERIODIC TABLE

 The periodic table is divided into sections

The first section contains the elements in Groups 1 and 2 and 13-18

These 8 groups are the representative elements

The representative elements include metals, metalloids, and nonmetals

ZONES OF THE PERIODIC TABLE

Groups 3-12 are the transition elements

These elements are all metals

The inner transition elements (the lanthanide and actinide series) are located below the below the main table

Why?

ZONES OF THE PERIODIC TABLE

 To save space! The periodic table would be too wide if they were included in the main table

(They are called the lanthanide and actinide series because the lanthanide series follows the element lanthanum and the actinide follows actinium)

METALS, NONMETALS AND METALLOIDS

 Metal- an element that has luster, is a good conductor of heat and electricity, and is malleable

All metals, except mercury, are solids at room temperature

METALS, NONMETALS AND METALLOIDS

 Nonmetals- usually gases or brittle solids at room temperature, they are poor conductors of heat and electricity

There are only 17 nonmetals, but they are very important. They include carbon, sulfur, nitrogen, oxygen, phosphorous and iodine.

Elements we cannot live without!

METALS, NONMETALS AND METALLOIDS

 Metalloids- elements that share some properties with metals and some with nonmetals

Metalloids are located between metals and nonmetals on the periodic table

Each element is represented on the periodic table by box called an element key

The element key indicates the element’s name, atomic number, symbol and average atomic mass

There may be a logo indicating whether the element is a solid, liquid or gas at room temperature

Balloon- gas, Cube= solid, Drop= liquid Bulls-eye= synthetic elements

SYMBOLS FOR THE ELEMENTS

 The symbols for the elements are either one or two letter abbreviations

Usually they make sense for example: O for oxygen

Sometimes they are a bit weird for example: Au for gold

(Au came from Aurum “shining dawn” in Latin)

REPRESENTATIVE ELEMENTS Chapter 15 Section 2

GROUPS 1 AND 2

 Always found in nature combined with other elements

 Called active metals because they like to form compounds with other elements

 They are all metals except for hydrogen

ALKALI METALS  Group 1 metals are called

Alkali Metals

-silvery solids with low densities and low melting points

-increase in reactivity (the tendency to combine with other elements) as you move from top to bottom on the periodic table

(Sodium chloride in table salt, lithium in batteries)

ALKALINE EARTH METALS

 Group 2 metals are called

Alkaline Earth Metals

-denser, harder, and has a higher melting point than the alkali metal in the same period

-reactive, but not as reactive as the alkali metals

(Beryllium in emeralds, Magnesium in chlorophyll)

GROUPS 13-18

 These elements are not all solid metals (groups 1 and 2 are all solid metals)

 One group can have metals, nonmetals, and metalloids

 One group can contain elements that are solids, liquids, or gases

THE BORON FAMILY

 Group 13

-all metals except for boron (a brittle, black metalloid)

-boron-coated cookware won’t crack when moved from cold to hot

-aluminum is used to make cans, cookware, house siding and baseball bats

-gallium is used to make computer chips

THE CARBON GROUP

 Group 14 -carbon is a nonmetal -silicon and germanium are metalloids -tin and lead are metals

Carbon exists as an element as diamond and graphite. It is also in all living things

Silicon is found in sand (ground up bits of quartz, made of silicon and oxygen)

 Silicon and germanium, metalloids, are semiconductors

Semiconductor Something that doesn’t conduct electricity as

well as a metal, but conducts electricity better than a nonmetal

Semiconductors are most often used in electronics (computer chips)

 Tin and lead are the heaviest elements in Group 14

-lead is used in car batteries, as protection from nuclear reactors and x-ray equipment

-tin is used for pewter and toothpaste

THE NITROGEN GROUP

 Group 15 -Nitrogen and phosphorous are the nonmetals of

this group

-both are needed by living things

-ammonia is a gas that contains nitrogen and hydrogen, when dissolved in water it can be used as a cleaner (Windex), it can also be used as a fertilizer and used to make nylon

-phosphorous is needed for healthy teeth and bones -plants also need phosphorous and it is an

ingredient in most fertilizers

THE OXYGEN GROUP

 Group 16 -Oxygen and sulfur are necessary for life -tellurium and polonium (the heavier elements in

this group) are metalloids

~20% of Earth’s atmosphere is oxygen There is a lot of oxygen in rocks and minerals

because it easily combines with other elements

-sulfur is a solid, yellow nonmetal (very stinky!) -selenium is used in solar cells, copiers, and

camera materials because it conducts electricity when exposed to light

THE HALOGEN GROUP

 Group 17 -all are nonmetals except for astatine (radioactive

metalloid)

-called halogens because they are “salt formers” -all halogens form salts with sodium and other

alkali metals -halogens decrease in reactivity down the group

(iodine less reactive than bromine which is less reactive than chlorine which is less reactive than fluorine)

THE NOBLE GASES

 Group 18 -called the noble gases because they like to be

alone

-they rarely combine with other elements

-found in nature as uncombined elements

-VERY LOW REACTIVITY

 Neon signs do not necessarily contain neon  Each noble gas produces a different color -Helium glows yellow -neon glows red-orange -argon glows blue

Krypton + nitrogen keeps light bulb filaments from burning out

Radon is a radioactive gas produced from decaying uranium. It continues to release radiation and if breathed in over time can cause lung cancer

TRANSITION ELEMENTS Chapter 15 section 3

 All the transition elements are metals

 Across any period, the properties of the transition elements change less noticeably than the representative elements

 Most of the transition elements are found combined with other elements in ores (minerals or an aggregate of minerals from which a valuable constituent, especially a metal, can be profitably mined or extracted)

 Few transition elements are found as pure elements (Gold, Silver)

THE IRON TRIAD

  Iron, cobalt, and nickel (all in period 4) have very similar properties and are known as the “iron triad”

 Magnetic properties

 Steel is made from iron + other metals + carbon. The “other metals” determine how strong the steel is

 Most transition metals have higher melting points than the representative elements

 Tungsten has the highest melting point of any metal (3,410C)

 Mercury has the lowest melting point of any metal (it’s a liquid) (-39C)

 Ruthenium, rhodium, palladium, osmium, iridium and platinum (sometimes referred to as the “platinum group” do not combine easily with other elements and are often used as catalysts (substances that can speed up reactions but are not themselves changed in the process)

 Nickel, zinc, and cobalt can also be used as catalysts

THE LANTHANIDES

 Also called “rare earths”, because once they were thought to be rare (they are, in fact, not so rare)

 Usually combined with oxygen in Earth’s crust

 Soft metals that can be cut with a knife

 The elements are very similar and often occur in the same ore

THE ACTINIDES   All are radioactive

  Only thorium, protactinium, and uranium are found naturally on Earth

  Uranium is found in Earth’s crust (long half-life, 4.5 billion years)

  All the other actinides are synthetic elements (made in labs and nuclear reactors)

  Plutonium fuels nuclear power plants

  Americium is used in smoke detectors

  Californium-252 is used in cancer radiation therapy

HOW SYNTHETIC ELEMENTS ARE MADE

The nuclei of different atoms fuse to form a new (often short-lived) synthetic element.

Energy and at least one subatomic particle are usually given off in the process

In this reaction, 2 isotopes of hydrogen (tritium and deuterium) are fused to form helium. A neutron and energy are given off.