lecture 2 - periodic table

8/10/2019 LECTURE 2 - Periodic Table

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PERIODIC TABLE

Further ChemistryGill Daddow


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Mendeleev Creator of the

modern Periodic Table


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PERIODS

Horizontal rows are calledPERIODS.

Atomic number increases by 1 asyou read from left to right.

Atoms in the same period do

not necessarily have similar

properties.

Atoms towards the left of the

period are metals

Atoms towards the right third of

the period are non metals


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GROUPS

Vertical columns are calledGROUPS

Members of same group haveSAME CHEMICAL PROPERTIES

Graduation

in their chemical reactivity

Size of the atoms

increase

as you read

down

the group

Groups are usually numbered from 1 to 18

Older versions use Roman numerals like this


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Older version of numbering.


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and sometimes the s,p,d

block elements are shown


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GROUP I

ALKALI METALS

Silvery, soft (or liquid at RT)

Each has only one electron in its outermost shell

Make 1+ions(oxidation number of 1

+

)

React readily and vigorously with water to produce ahydroxide hence the name alkali)


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Task: Know this balanced equation

2K

(s)

+ 2H

2

O

(l)

2KOH

(aq)

+ H

2(g)


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GROUP I

React readily with oxygen in air to form metal oxideseg.

4Li + O

2

2Li

2

0

Never found in the environment as NATIVE METALS Stored under oil or in vacuum


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GROUP I

Also found in nature as their chloride

compounds eg.

Halite NaCl

Sylvite KCl


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GROUP I

The further w yfrom the nucleus theoutermost electron is - the e sierit is to be

lost to another atom.

It takes much less energy for ceasium toform its ion than lithium to form its ion. ie.

it has a lower IONISATION ENERGY

.


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Ionisation energy is governed by:

the charge on the nucleus,

the amount of screening by the inner electrons,

the distance between the outer electrons and the nucleus.


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GROUP I

The radius of an atom is governed by.. the number of layers of electrons around the nucleus

the pull the outer electrons feel from the nucleus.


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GROUP 2

ALKALINE EARTH METALS

Also react with water to produce a hydroxide

Each has only two electrons in its outermost shell

Make 2+ions (oxidation number of 2+)

Chemical activity increases with increasing radiustherefore increases as you read down the group.


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GROUP 2

Not found as native elements but as compounds.

Here are just a few examples

Beryllium silicate (beryl)

Magnesium carbonate (magnesite)

Calcium carbonate (calcite)

Strontium carbonate (strontianite)

Barium sulfate (barite)


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Hard Water

Hard water contains appreciable amounts ofcalciumand magnesiumsalts dissolved in it.

Cause scumwith soap and scalein boilers &kettles.

Calcium & magnesium salts originate from thecarbonates in underlying rocks.


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Radium

Radioactivechemical element Pure white but readily oxidizeson exposure to air,

turning black. Found in trace amounts in uraniumores. Extremely radioactive.

Most stable isotope, 226Ra, has a half-lifeof 1602years Decaysinto radongas.
http://en.wikipedia.org/wiki/Radioactivehttp://en.wikipedia.org/wiki/Chemical_elementhttp://en.wikipedia.org/wiki/Oxidizehttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Isotopehttp://en.wikipedia.org/wiki/Half-lifehttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radonhttp://en.wikipedia.org/wiki/Radonhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Half-lifehttp://en.wikipedia.org/wiki/Half-lifehttp://en.wikipedia.org/wiki/Half-lifehttp://en.wikipedia.org/wiki/Isotopehttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Oxidizehttp://en.wikipedia.org/wiki/Chemical_elementhttp://en.wikipedia.org/wiki/Radioactive


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TRANSITION METALS

Elements in central part of the table

Sometimes called groups IIIB, IVB, VB More recently called groups 3-12

Called transition as their chemical and physical properties vary

Some have variable oxidation numbers becauseelectrons can jump between the outermost shell andthe partially filled penultimate shell eg.

Cu(I) & Cu (II)

Fe(II) & Fe(III)

Mn(II) & Mn(IV) & Mn(VII)

Valuable eg. construction materials

catalysts for chemical reactions (especially nickel, platinum, vandium)

Know

this!


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TRANSITION METALS

The less reactive transition metals can be found naturally as

NATIVE METALS

Copper

Mercury

Silver

Gold

Platinum


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TRANSITION METALS

Purifying Copper by Electrolysis

At the anode Cu

(s)

Cu

2+

(aq)

- 2e

-

At the cathode Cu

2+

(aq)

+ 2e

-

Cu

(s)


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COPPER

Relatively unreactive therefore corrodes(oxidises) slowly.

Conducts electricity

Malleable and ductile (sheets, pipes, wires)

Alloyed with tin (bronze) and with zinc (brass)to improve its mechanical properties eg. Reduce

friction.


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IRON

Iron is found as a multitude of iron containing

compounds. Hematite is one of the most common

ores and contains iron as iron oxide.


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Extracting Iron from Iron Oxide

Smelting with carbon


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Titanium

Lightweight but strong Protected by an oxide layer so doesnt corrode Withstands very high temperatures - used in

nuclear reactors Used in air-craft and racing bikes and prosthetichips.


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POOR METALS

Generally taken to include aluminium, gallium, indium, tin, thallium,

lead, and bismuth. Occasionally germanium, antimony, and polonium

Compared to transition metals

Have lower meltingand boiling points

Softer

Again used in construction and as catalysts.
http://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Galliumhttp://en.wikipedia.org/wiki/Indiumhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Thalliumhttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Bismuthhttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Antimonyhttp://en.wikipedia.org/wiki/Poloniumhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Poloniumhttp://en.wikipedia.org/wiki/Antimonyhttp://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/Bismuthhttp://en.wikipedia.org/wiki/Leadhttp://en.wikipedia.org/wiki/Thalliumhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Indiumhttp://en.wikipedia.org/wiki/Galliumhttp://en.wikipedia.org/wiki/Aluminium


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METALLOIDS


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METALLOIDS

The elements in groups 13 to 16show a mixture of physical and chemicalproperties.

A metalloid (semi-metal) has the physical appearance and properties of a metalbut behaves chemically like a nonmetal.

The distinction between metals and metalloids and nonmetals is not precise.

SILICON, BORON and GERMANIUM used as SEMI-CONDUCTORS


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SILICON

The second most abundant element in the Earths crustafter oxygen

Seldom found naturally in its native elemental form

Usually silicon dioxide (aka silica)

Or as silicate compounds SiO4

4-

Silicon bond together to form long chain compoundscalled silicones


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GROUP 13-17

NON METALS

Poor conductors of electricity (except graphite)

Not ductile or malleable

Low melting points many are liquid or gases at room temperature

On their own they can form anions eg. C2-, O2-, S2-(therefore negative oxidation numbers)

Make covalen bonds with oxygen to form anions eg. CO3

2-

, SO

4

2-

, NO

3

-

, SiO

4

4-

,PO

4

3-


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GROUP 13-17

NON METALS

When carbon, nitrogen, phoshphorus or sulfur react with oxygen, they for oxides which dissolve in water to form the

following acids

Carbonic acid H2CO3Nitric acid HNO3

Phosphoric acid H3PO4Sulfuric acid H2SO4


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Group 17 (VII)

HALOGENS

Chemically similar each has SEVEN electrons in its outermost shell

They make 1-ions (oxidation number of 1-)

Also make covalent compounds

Element is diatomic ie. F

2

, Cl

2

, Br

2

, I

2


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Group 17 (VII)

HALOGENS

The further away from the nucleus the outermost shellis, the more difficult it is for the atom to gain an

electron from another atom.

Fluorine readily and vigorously reacts and ionises &

iodine is the least reactive of the group


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Electronegativity

Electronegativity is a measure of thetendency of an atom to attract electrons.

The Pauling scale is the most commonlyused. Fluorine (the most electronegativeelement) is assigned a value of 4.0, and

values range down to caesium and franciumwhich are the least electronegative at 0.7.


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Chlorine, Bromine & Iodine


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Group 18 (0)

NOBLE GASES

Group 0 elements have complete outer shell of electrons

Chemically inert - only a few compounds eg. XeF2

They are all monatomic gases

Have low boiling points.

lecture 2 - periodic table

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