Topic 4Periodic Table

Learning OutcomesBy the end of this topic, you should be able to:

Analyse the periodic table.

Summarise the electronic structures and periodic table.

Identify properties and usages of transition elements.

Learning OutcomesBy the end of this topic, you should be able to:

Identify the electronic structure, group trends, physical properties and chemical properties of Group 1 and Group 17.

Summarise noble gases.

Identify the properties and classification of Period 3 elements.

History of the Periodic Table:Antoine Lavoisier (17431794)

History of the Periodic Table:Johann Dobereiner (17801849)This classification was unsuccessful because the classification was limited to a few elements only.

Then, other scientists realised that there was a relationship between the properties and atomic masses of the elements.

History of the Periodic Table:John Newlands (18371898)Newlands arranged all the known elements horizontally in the ascending order of their atomic masses.

Each row consisted of seven elements.

He found that elements with similar properties recurred at every eighth element.

This arrangement was known as the Law of Octaves.

History of the Periodic Table:John Newlands (18371898)However, this law was only obeyed by the first 17 elements.

There were no positions allocated for elements yet to be discovered.

However, Newlands contibution to the development of the periodic table was very important as he was the first chemist who discovered the existence of periodicity in the elements.

History of the Periodic Table:Lothar Meyer (18301895)Lothar Meyer plotted a graph of atomic volume against atomic mass for all known elements.

He showed that the properties of the elements were in a periodic pattern with their atomic masses.

Hence, Meyer also proved that the properties of the elements recur periodically.

History of the Periodic Table:Dmitri Mendeleev (18341907)Mendeleev - arranged the known elements in order of increasing atomic mass in successive sequences so that elements with similar chemical properties fell into the same column.

He was able to predict the properties of undiscovered elements and left gap for these elements.

A portion of Mendeleevs periodic table, giving the atomic masses known at the time and showing some of the holes representing unknown elements. There is an unknown element (which turned out to be gallium, Ga) beneath aluminum (Al) and another one (which turned out to be germanium, Ge) beneath silicon (Si).History of the Periodic Table:Dmitri Mendeleev (18341907)

History of the Periodic Table:Henry J. G. Moseley (18871915)Henry J. G. Moseley studied the x-ray spectrum of elements.

He rearranged the elements in the ascending order of their proton numbers.

Modern Periodic TableA periodic table is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties.

The periodic table of the elements is organized into 18 groups and 7 periods. Elements are arranged according to proton number.

The Periodic Table

Analysis of The Periodic TableEach horizontal row (there are 7 of them) is called a period.

Each vertical column is called a group.

Elements in a group have similar chemical properties.

Those within a period have properties that change progressively across the table.

Analysis of The Periodic TableGroups

There are 18 groups of elements in the periodic table.

Group 1 - Alkali metalGroup 2 - Alkaline earth metalGroup 3 to Group 12 - Transition elementGroup 17 - HalogenGroup 18 - Noble gas

Group 1 Alkali metalsThe alkali metals: lithium, sodium, potassium, rubidium, cesium, and franciumElements in this group are highly reactive and form alkaline (basic) solutions with water.

Group 2 Alkaline earth metals The alkaline earth metals: beryllium, magnesium, calcium, strontium, barium, and radiumElements in this group also form alkaline (basic) solutions with water but are less reactive than the Group 1 metals.

Group 17 Halogens The halogens (means salt formers): fluorine, chlorine, bromine, iodine, and astatineElements in this group form salts with metals.

Group 18 Noble gases The noble gases: helium, neon, argon, krypton, xenon, and radonElements in this family have such a low reactivity that they were formerly known as the inert gases.

Metal elementsMetallic character increases from top to bottom and decreases from left to right.

Nonmetal elementsNonmetallic character decreases from top to bottom and increases from left to right.

Semimetal elements (or metalloids)Metalloids show some properties that are characteristic of both metals and nonmetals.

Semimetal elements (or metalloids)Many of the metalloids, such as silicon, germanium and antimony, act as semiconductors, which are important in solid-state electronic circuits.

Semiconductors are insulators at lower temperatures and become conductors as higher temperatures

Analysis of The Periodic TableGroups

Metals - Elements in Groups 1 to 13

Non-metalsElements in Groups 15, 16, 17 and 18Carbon and silicon from Group 14

Some physical properties of metals and nonmetals:

MetalsNonmetalsHigh electrical conductivity that decreases with increasing temperaturePoor electrical conductivity (except carbon in the form of graphite)High thermal conductivityGood heat insulators (except carbon in the form of diamond)Metallic gray or silver luster (except copper and gold)No metallic lusterAlmost all are solids (except mercury; cesium and gallium melt in protected hand) Solids, liquids or gasesMalleable (can be hammered into sheets)Brittle in solid stateDuctile (can be drawn into wires)Nonductile

Analysis of The Periodic TablePeriods

Short periods (Period 1 3)

Long periods (Period 4 7)

Lanthanide Series (elements with proton number 58 to 71)

Actinide Series (elements with proton number 90 to 103)

Electronic Structures and The Periodic TableValence electrons are electrons found in the outermost occupied shell of an atom.

All members of the same group have the same number of valence electrons.

Electronic Structures and The Periodic TableThe position of the period of an element in the periodic table is determined by the number of shells occupied with electrons in the atom.

Electronic Structures and The Periodic TableKeep in mind that the chemical properties of the elements in a period are the same but the physical properties of these elements change gradually. (pg 87)

Electronic Structures and The Periodic TableWhen going across a period from left to right,

Atomic radius decrease

Electronegativity (the ability of an element to pull the electron to itself) increase

Metal characteristics - decrease Metal semi-metal non-metal

Oxide characteristicsAlkaline acidic

Transition MetalsElements between Group 2 and Group 13

All transition elements are metals: Silvery surface Hard High density Ductile and malleable High melting and boiling point Good electrical conductivity

Transition MetalsFour special characteristics:

Transition MetalsForm Coloured Compounds

Transition MetalsForm Coloured CompoundsThe colours of gemstones and precious stones occur naturally due to the presence of the transition elements in them:

Emerald is green because it contains nickel and iron. Ruby is red due to the existence of chromium.

Transition MetalsForm Coloured CompoundsAqueous solutions of transition element compounds can react with sodium hydroxide solution and ammonia solution to form coloured precipitates of metal hydroxides.

The precipitates formed are coloured because these are compounds of transition elements.

Transition MetalsHas Variable Oxidation NumbersExamples:Iron(II), Fe2+, and Iron(III), Fe3+Copper(I), Cu+, and Copper(II), Cu2+

Transition MetalsMany Transition Elements and Their Compounds Have Catalytic PropertiesA catalyst is a substance that speeds up a reaction but does not change chemically after a reaction.

Transition MetalsMany Transition Elements and Their Compounds Have Catalytic Properties

Transition MetalsCan Form Complex IonsA complex ion is a polyatomic cation or anion consisting of a central metal ion with other groups bonded to it.

Example: tetraamminecopper(II) ion, [Cu (NH3)4]2+

Transition Metals:Industrial Uses

Group 1 Alkali metalsThe alkali metals: lithium, sodium, potassium, rubidium, cesium, and franciumElements in this group are highly reactive and form alkaline (basic) solutions with water.

Group 1Alkaline metals - can react with water to form alkaline solutions.

Group 1

Group 1Physical Properties:

Soft solids and can be easily cut

Grey solids with shiny silvery surfaces

Surfaces will turn dull very fast when exposed to air. Alkali metals are very reactive; hence, they react rapidly with oxygen and water vapour in the air when exposed. Thus, they have to be kept in paraffin oil.

Group 1Physical Properties:

Low density compared to heavy metals (iron and copper)

Good conductors of heat and electricity

Group 1Atomic radius increases down the group.

The number of filled electron shells increases down the group.

The density increases down the group The increase in mass of the atom is greater than the increase in the atomic radius of the atom.

Group 1The melting point decreases as we go down Group 1 .

The metallic bond between the atoms becomes weaker as the atomic radius increases.

Group 1The electropositivity (the ability of an atom to lose an electron and form a positive ion) of the metal increases down the group.

The further the position of the valence electron from the nucleus, the weaker the force of attraction between the nucleus and the valence electron.

Hence, the elements lose the single valence electron more easily.

Group 1Chemical Properties:

React with water to liberate hydrogen gas and form metal hydroxide

React with oxygen to produce metal oxides

React with chlorine to produce metal chloride

React with bromine to produce metal bromide

Oxygen And The Oxides Reactions of Metal Oxides with Water:The oxides of the Group 1 metals dissolve in water to give solutions of strong bases.

Na2O(s) + H2O(l) 2NaOH(aq) Sodium oxide sodium hydroxide

Group 17 Halogens The halogens (means salt formers): fluorine, chlorine, bromine, iodine, and astatineElements in this group form salts with metals.

Group 17

Group 17Halogen - salt producer Very reactive elements.Most of them exist naturally as halide salts.

Halogens are non-metals and exist as diatomic covalent molecules.

Group 17All elements of Group 17 have seven valence electrons.

Group 17

Group 17Physical Properties:

Insulators of heat and electricity

Low melting and boiling points Poor forces of attraction between the molecules

Low density

Group 17Atomic radius increases down the group.

The number of filled electron shells increases down the group.

The density increases down the group The increase in mass of the atom is greater than the increase in the atomic radius of the atom.

Group 17The melting and boiling point increases as we go down Group 17 .

The molecular size increases down the group.

As the molecular size of halogens increases, the van der Waals forces of attraction between the molecules become stronger.

More heat is required to overcome the forces of attraction between the molecules.

F2 and Cl2 gas; Br2 liquid; I2 and At2 - solids at room temperature

Group 17The colour of halogen becomes darker down the group.

Fluorine - pale-yellow gasChlorine - greenish-yellow gasBromine - reddish-brown liquid Iodine - purplish-black solid

Group 17The electronegativity (the tendency of an atom to attract an electron and form a negative ion) of halogens decreases from fluorine to iodine.

This is because as the atomic radius becomes larger.

The force of attraction between the nucleus and the valence electrons becomes weaker.

The strength of the nucleus to attract electrons becomes weaker.

Group 17Chemical Properties:

The reactivity of halogen decreases as they go down the group.

Halogens can easily gain one electron to achieve a stable octet electron arrangement and therefore are good oxidising agents.

As the reactivity of halogens decreases down the group, their strength as oxidising agents also decreases down the group.

Group 17Chemical Properties:

Group 17 elements exhibit similar chemical properties when they react with:

(a) Water(b) Iron(c) Cold sodium hydroxide solution

Group 17Chemical Properties:

React with water to produce acidic solutions.

However, the solubility of halogens in water decreases when going down group 17.

Chlorine and bromine dissolve readily in water, forming acidic solutions which turn blue litmus paper red.

Group 17Chemical Properties:

React with water to produce acidic solutions.

The solution formed is also bleaching agents which turn the litmus paper white due to the presence of hypochlorous acid or hypobromus acid.

Iodine is only very slightly soluble in water.

Group 17Chemical Properties:

React with hot iron to produce a iron(III) halides solid

Chlorine, bromine and iodine react with hot iron to produce a brown iron(III) halides solid.

The reactivity of the halogens in their reaction with iron decreases from chlorine to bromine.

Group 17Chemical Properties:

React with cold sodium hydroxide solution to produce water and a colourless solution containing salts of sodium halide and sodium halate(I).

Cl2 + 2NaOH NaCl + NaOCl + H2O

The reactivity decreases from chlorine to iodine.

Group 18 Noble gases The noble gases: helium, neon, argon, krypton, xenon, and radonElements in this family have such a low reactivity that they were formerly known as the inert gases.

Group 18

Group 18Noble gases are chemically unreactive.

The atoms have a stable electronic structure.

Helium atoms have two electrons in their only electron shell (duplet electron arrangement)

The outermost shell of the atoms of the other noble gases has eight electrons (octet electron arrangement)

Group 18Exist as monoatom gases.

Colourless and insoluble in water.

Cannot conduct electricity and are poor conductor of heat.

Group 18

Group 18Have very low melting and boiling points because noble gases are held together by weak Van der Waals forces of attraction.

Have very low densities but the density increases slowly when going down the group because the increase in atomic mass is greater than the increase in volume.

Period 3

Period 3When going across Period 3 from left to right,

Atomic radius decrease

Electronegativity (the ability of an element to pull the electron to itself) increase

Electronegativity TREND: Electronegativity decreases down a group and increases within a period.

Period 3Metals form oxides with basic properties only.

Non-metals form oxides with acidic properties only.

Semi-metal form oxides with both acidic and basic properties. These oxides are known as amphoteric oxides.

Period 3When going across a period from left to right,

Metal characteristics - decrease Metal semi-metal non-metal

Oxide characteristicsAlkaline Amphoteric Acidic

Chloride and Hydride for Elements in Period 3

Chloride and Hydride for Elements in Period 3When going across Period 3 from left to right:

The bonding changes from ionic to covalent.

They react with water rather than dissolve in it.

The compound solution changes from neutral to acidic

Oxygen And The Oxides Reactions of Nonmetal Oxides with Water:Nonmetal oxides are called acid anhydrides (or acidic oxides) because many of them dissolve in water to form acids.

Nonmetal oxide + water Ternary Acid (contains 3 elements)

CO2(g) + H2O(l) H2CO3(aq) carbonic acid