Chemical Properties and PeriodicityALKALI METALS:

Physically they are solid, soft, malleable, conductors and have low density (large atoms) and low melting points compared with other metals (only 1 e- contributes to the metallic bond).

These last two properties decrease as we move down the group, because the size of the atom increases.

Have 1 e- in the outer level

Form 1+ ions

The alkali metals are very reactive

Chemical Properties and Periodicity

They react with oxygen or with halogens to form binary ionic compounds:

Some reactions of alkali metals:

2Li2O(s)

2KCl(s)

2NaBr(s)

2NaOH(aq) + H2(g)

4Li (s) + O2(g)

2K(s) + Cl2 (g)

2Na(s) + Br2 (l)

They react vigorously with water:

Na(s) + 2H2O(l)

They must be stored in kerosene because they react explosivelywith water from the atmosphere…

…Reactions of alkali metals

2MOH(aq) + H2(g)M(s) + 2H2O(l)

This reaction is the same for all alkali metals but it becomes more vigorous as we move down the group (Slow with Li, vigorous with Na and violent with K).

M+(aq) and OH-(aq)

Very alkaline (basic) solution

Basic Information

Name: Lithium Symbol: Li Atomic Number: 3 Atomic Mass: 6.941 amu Melting Point: 180.54 °C (453.69 °K, 356.972 °F)

Boiling Point: 1347.0 °C (1620.15 °K, 2456.6 °F) Number of Protons/Electrons: 3 Number of Neutrons: 4 Classification: Alkali Metal Crystal Structure: Cubic Density @ 293 K: 0.53 g/cm3 Color: silvery

Atomic Structure

                                                              

 

Number of Energy Levels: 2

First Energy Level: 2 Second Energy Level: 1

http://www.chemicalelements.com/elements/li.html

Isotope Half Life

Li-6 Stable

Li-7 Stable

FACTS

Date of Discovery: 1817 Discoverer: Johann Arfvedson Name Origin: From the Greek word lithos (stone) Uses: batteries, ceramics, lubricants Obtained From: passing electric charge through melted lithium chloride, spodumene

ISOTOPES

http://www.chemicalelements.com/elements/li.html

http://www.westga.edu/~chem/courses/desc.inorg/490Jan14/sld005.htm

                                

Basic Information

Name: Sodium Symbol: Na Atomic Number: 11 Atomic Mass: 22.98977 amu Melting Point: 97.8 °C (370.95 °K, 208.04001 °F) Boiling Point: 552.9 °C (826.05005 °K, 1027.2201 °F) Number of Protons/Electrons: 11 Number of Neutrons: 12 Classification: Alkali Metal Crystal Structure: Cubic Density @ 293 K: 0.971 g/cm3 Color: silvery

Atomic Structure

Number of Energy Levels: 3

First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 1

http://www.chemicalelements.com/elements/na.html

Isotope Half LifeNa-22 2.6 years

Na-23 Stable

Na-24 14.96 hours

Facts

Date of Discovery: 1807 Discoverer: Sir Humphrey Davy Name Origin: soda (Na2CO3)

Symbol Origin: From the Latin word natrium (sodium) Uses: medicine, agriculture Obtained From: table salts and other foods

Isotopeshttp://www.chemicalelements.com/elements/na.html

http://www.westga.edu/~chem/courses/desc.inorg/490Jan14/sld005.htm

Number of Energy Levels: 4

First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 8 Fourth Energy Level: 1

Basic Information

Name: Potassium Symbol: K Atomic Number: 19 Atomic Mass: 39.0983 amu Melting Point: 63.65 °C (336.8 °K, 146.57 °F) Boiling Point: 774.0 °C (1047.15 °K, 1425.2 °F) Number of Protons/Electrons: 19 Number of Neutrons: 20 Classification: Alkali Metal Crystal Structure: Cubic Density @ 293 K: 0.862 g/cm3 Color: silvery

http://www.chemicalelements.com/elements/k.html

Isotopes

Isotope Half Life

K-39 Stable

K-40 1.28E9 years

K-41 Stable

K-42 12.4 hours

K-43 22.3 hours

Facts

Date of Discovery: 1807 Discoverer: Sir Humphrey Davy Name Origin: potash Symbol Origin: From the Latin word kalium Uses: glass, soap Obtained From: minerals (carnallite)

http://www.chemicalelements.com/elements/k.html

http://www.westga.edu/~chem/courses/desc.inorg/490Jan14/sld006.htm

http://www.chemicalelements.com/elements/rb.html

If you want information about Rb, Cs and Fr use the following links

Rb:Cs:

Fr:

http://www.chemicalelements.com/elements/cs.htmlhttp://www.chemicalelements.com/elements/fr.html

http://www.westga.edu/~chem/courses/desc.inorg/490Jan14/sld006.htm

All the halogens exist in the form of diatomic molecules: F2, Cl2, Br2, I2, At2

Physically the first two, F2, Cl2, are gases, Br2 is liquid, I2 is a solid that sublimates at room temperature.

They show different colors, for example Chlorine is green, Iodine is black and Bromine is red-brown.

They are slightly soluble in water (because they are non polar): X2 + H2O H+ + X- + HOX

In polar solvens (like H2O and ethanol) Iodine forms a brown solution, but in non-polar solvents it forms a purple solution.

The HalogensThe Halogens

They have 7 e- in the outer level, so they need 1 e- to become isoelectronic with a noble gas.Therefore they form 1- ions.They react with metals to form binary compounds:

2LiF(aq)

2KCl(aq)

2NaBr(aq)

2Li (s) + F2(g)

2K(s) + Cl2 (g)2Na(s) + Br2 (l)

Some reactions of halogens

These halides are usually white and soluble in water

The insoluble halides are the ones formed with silver likeAgCl, AgBr and AgI : Ag+(aq) + X-(aq) AgX(s).

The halides of Lead (II) are insoluble but can be dissolved hot water. Lead (II) iodide (PbI2) is yellow.

The previous reactions and properties can be used to test for the presence of halides as follows: •First add nitric acid to prevent other substances like carbonates to form precipitates and confuse the results. •Then add silver nitrate. •NaCl(aq) + AgNO3 (aq) NaNO3(aq) + AgCl(s)•The formation of a precipitate indicates the presence of chloride, iodide or bromide ions. (Fluorine doesn’t form a precipitate)• AgCl(s) is white and darkens with sunlight• AgBr(s) is white• AgI(s) is pale yellow

Cont…Some reactions of halogens

Other reactions of halogensOther reactions of halogens

The halogens can undergo

SINGLE REPLACEMENT REACTIONS:

X2 + MY Y2 + MX

F2 (g) + 2NaCl(aq) Cl2(g) + 2NaF(aq)

Example:

A +BC A +BC AC + B AC + BAn element takes the place of another element in a compound.

N.R.

It could be a metal taking the place of another metal or hydrogen.

Mg(s) + FeSO4(aq) MgSO4 (aq) + Fe(s)

Magnesium is more active than Iron

Fe(s) + MgSO4 (aq)

Review of Single Review of Single

ReplacementReplacement ReactionsReactions

It could be also a halogen taking the place of another halogen.

2 KCl(aq) + Br2 (aq)Cl2(g) + 2KBr(aq)

Chlorine is more active than Bromine!

Br2 (aq) + KCl(aq) N.R.

……cont…Single Replacement cont…Single Replacement

An atom or ion is oxidized when it loses electrons in a reaction

An atom or ion is reduced when it gains electrons in a reaction

Halogens tend to be reduced to form thenegative ion (halide)

An atom that tends to be reduced is an oxidizing agent,because it makes other elements to be oxidized.

Halogens act as oxidizing agents in a single replacement reaction

The oxidizing power decreases down a group becausethey have less tendency to be reduced (becoming negative).

Oxidizing powerOxidizing power

That is why a higher halogen in the PT canreplace a lower halogen and form its salt.

But a lower halogen in the PT cannot replaceA higher halogen

This could be also expressed in the following way:

……Cont…Oxidizing powerCont…Oxidizing power

Cl2(g) + 2KI(aq) 2 KCl(aq) + I2 (aq)

KCl(aq) + I2 (aq) NR

Cl2(g) + 2I-(aq) 2 Cl-(aq) + I2 (aq)

2 Cl-(aq) + I2 (aq) Cl2(g) + 2I-(aq)

                            

Basic Information

Name: Fluorine Symbol: F Atomic Number: 9 Atomic Mass: 18.998404 amu Melting Point: -219.62 °C (53.530006 °K, -363.31598 °F) Boiling Point: -188.14 °C (85.01 °K, -306.652 °F) Number of Protons/Electrons: 9 Number of Neutrons: 10 Classification: Halogen Crystal Structure: Cubic Density @ 293 K: 1.696 g/cm3 Color: Greenish Number of Energy Levels: 2

First Energy Level: 2

Second Energy Level: 7

http://www.chemicalelements.com/elements/f.html

Isotopes

Half Life

F-18 1.8 hours

F-19 Stable

Facts

Date of Discovery: 1886 Discoverer: Joseph Henri Moissan Name Origin: From the Latin word fluo (flow)

Uses: Refrigerants Obtained From: mineral fluorite

Isotope

Basic Information

Name: Chlorine Symbol: Cl Atomic Number: 17 Atomic Mass: 35.4527 amu Melting Point: -100.98 °C (172.17 °K, -149.764 °F) Boiling Point: -34.6 °C (238.55 °K, -30.279997 °F) Number of Protons/Electrons: 17 Number of Neutrons: 18 Classification: Halogen Crystal Structure: Orthorhombic Density @ 293 K: 3.214 g/cm3 Color: green

Number of Energy Levels: 3

First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 7

http://www.chemicalelements.com/elements/f.html

Isotope Half Life

Cl-35 Stable

Cl-36 301000.0 years

Cl-37 Stable

Cl-38 37.2 minutes

Facts

Date of Discovery: 1774 Discoverer: Carl Wilhelm Scheele Name Origin: From the Greek word khlôros (green) Uses: Water purification, bleaches Obtained From: Salt

http://www.chemicalelements.com/elements/f.html

Atomic Mass: 79.904 amu Melting Point: -7.2 °C (265.95 °K, 19.04 °F) Boiling Point: 58.78 °C (331.93 °K, 137.804 °F) Number of Protons/Electrons: 35 Number of Neutrons: 45 Classification: Halogen Crystal Structure: Orthorhombic Density @ 293 K: 3.119 g/cm3 Color: Red

Number of Energy Levels: 4

First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 18 Fourth Energy Level: 7

Name: Bromine Symbol: Br Atomic Number: 35

Facts

Date of Discovery: 1826 Discoverer: Antoine J. Balard Name Origin: From the Greekword brômos (stench) Uses: Poisonous Obtained From: Sea Water

Isotope Half Life

Br-76 16.0 hours

Br-77 2.4 days

Br-79 Stable

Br-80 17.7 minutes

Br-80m

4.42 hours

Br-81 Stable

Br-82 1.5 days

Br-83 2.4 hours

Br-84 31.8 minutes

Br-85 2.9 minutes

                                         

Number of Energy Levels: 5

First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 18 Fourth Energy Level: 18 Fifth Energy Level: 7

Basic Information

Name: Iodine Symbol: I Atomic Number: 53 Atomic Mass: 126.90447 amu Melting Point: 113.5 °C (386.65 °K, 236.3 °F) Boiling Point: 184.0 °C (457.15 °K, 363.2 °F) Number of Protons/Electrons: 53 Number of Neutrons: 74 Classification: Halogen Crystal Structure: Orthorhombic Density @ 293 K: 4.93 g/cm3 Color: blackish

http://www.chemicalelements.com/elements/i.html

Facts

Date of Discovery: 1811 Discoverer: Bernard Courtois Name Origin: From the Greek word iôdes (violet) Uses: required in humans Obtained From: sodium and potassium compounds

IsotopesIsotope/ Half LifeI-122 - 3.6 minutesI-123 - 13.2 hoursI-124 - 4.2 daysI-125 - 60.1 daysI-126 - 13.0 daysI-127 - StableI-128 - 25.0 minutesI-129 - 1.57E7 years

Isotopes ..cont…Isotope/ Half LifeI-130 - 12.4 hoursI-131 - 8.0 daysI-132 - 2.3 hoursI-133 - 20.8 hoursI-134 - 52.6 minutesI-135 - 6.6 hoursI-136 - 1.4 minutes

http://www.chemicalelements.com/elements/i.html

Name: Astatine Symbol: At Atomic Number: 85 Atomic Mass: (210.0) amu Melting Point: 302.0 °C (575.15 °K, 575.6 °F) Boiling Point: 337.0 °C (610.15 °K, 638.6 °F) Number of Protons/Electrons: 85 Number of Neutrons: 125 Classification: Halogen Crystal Structure: Unknown Density @ 293 K: Unknown Color: Unknown

                                                

Number of Energy Levels: 6

First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 18 Fourth Energy Level: 32 Fifth Energy Level: 18 Sixth Energy Level: 7

Isotopes

Isotope Half LifeAt-206

29.4 minutes

At-208

1.6 hours

At-211

7.2 hours

At-215

0.1 milliseconds

At-217

32.0 milliseconds

At-218

1.6 seconds

At-219

50.0 seconds

Facts

Date of Discovery: 1940 Discoverer: D.R. Corson Name Origin: From the Greek word astatos (unstable) Uses: No uses known Obtained From: Man-made

The metallic properties of the elements decrease from left to right in the PT.

The elements at´ the left have low ionization energy so they form + ions that form ionic compounds with negative ions.

The elements at the right form either ionic compounds with metals or covalent compounds with nonmetals.

Trends across a periodTrends across a period

The oxides of metals are ionic and if you dissolve them in water, they form basic solutions:

Na2O(aq) + H2O(l) 2NaOH(aq)

The oxides of non metals, towards the middle of thePT, are covalent and in water form acid solutions:

SO3(g) + H2O(l) H2SO4(aq)CO2(g) + H2O(l) H2CO3(aq) H+(aq) + HCO3

-(aq)

The chlorides of metals are ionic and dissolve in water to dissociate in the metal positve ion and the halogen negative ion (halide). The solutions are neutral: NaCl(aq) H2O(l) Na+(aq) + Cl-(aq)

Towards the middle of the table, the chlorides dissolve in water to give acidic solutions:SiCl4(aq) + 2 H2O(l) SiO2 + 4H+ + 4Cl-

Cont…Trends across a periodCont…Trends across a period