Periodic Trends in Chemical Properties

Chapter 3 – Green/Damji

Chapter 8 - ChangCopyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.

Group 1 Elements (ns1, n 2)

M M+1 + 1e-

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

8.6

(Alkali) Metals react with water to form hydroxides – which are bases.

(Alkali) Metals are electron donors, they form cations

Write the corresponding equation for sodium:

Group 1 Elements

Incr

easi

ng r

eact

ivity

8.6

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

2 Li(s) + 2 H2O(l) 2__________(aq) + H2(g)

2 Na(s) + 2 H2O(l) 2___________(aq) + H2(g)

2 K(s) + 2 H2O(l) 2 KOH(aq) + __________

slow and steady

vigorous

violent

Group 1 Elements (ns1, n 2)

4M(s) + O2(g) 2M2O(s)

8.6

(Alkali Metals react with oxygen to form metal oxides

2 M(s) + X2(g) 2 MX(s)

(Alkali) Metals react with halogens to form metal halides (salts)

Write the corresponding equation for sodium:

Write the corresponding equation for sodium:

Group 2 Elements (ns2, n 2)

M M+2 + 2e-

Be(s) + 2H2O(l) No Reaction

Incr

easi

ng r

eact

ivity

8.6

Mg(s) + 2H2O(g) Mg(OH)2(aq) + H2(g)

M(s) + 2H2O(l) M(OH)2(aq) + H2(g) M = Mg, Ca, Sr, or Ba

Group 3 Elements (ns2np1, n 2)

8.6

4Al(s) + 3O2(g) 2Al2O3(s)

2Al(s) + 6H+(aq) 2Al3+

(aq) + 3H2(g)

Group 4 Elements (ns2np2, n 2)

8.6

Sn(s) + 2H+(aq) Sn2+

(aq) + H2 (g)

Pb(s) + 2H+(aq) Pb2+

(aq) + H2 (g)

Group 5 Elements (ns2np3, n 2)

8.6

N2O5(s) + H2O(l) 2HNO3(aq)

P4O10(s) + 6H2O(l) 4H3PO4(aq)

Group 6 Elements (ns2np4, n 2)

8.6

SO3(g) + H2O(l) H2SO4(aq)

Group 7 Elements (ns2np5, n 2)

X2 + 2e- 2 X-1

X2(g) + H2(g) 2HX(g)

8.6

Halogens are electron acceptors, form anions

Halogens react with hydrogen to form hydrogen halides (which are acids )

Write the corresponding equation for chlorine:

Write the corresponding equation for bromine:

Group 7 Elements (ns2np5, n 2)

8.6

[Note: HCl is hydrochloric acid, a strong acid and HOCl (aq) is chloric acid, a weak acid ]

X2(g) + H2O(g) 2HX(aq) + HOX (aq)

Halogens react with water to form acids )

Write the corresponding equation for chlorine:

Group 7 Elements (ns2np5, n 2)

Incr

easi

ng r

eact

ivity

8.6

Metals react with halogens to form metallic halides…

The level of reactivity depends on the trends of reactivity for both the metal and the halogen…

Incr

easi

ng r

eact

ivity

Reactivity of Metals with Halogens

Ex: Which of the following pairs of chemicals will react most vigorously? Least vigorously?

K and Br2 Li and I2 Na and I2

Na and F2 K and F2 Li and Br2

2 M(s) + X2(g) 2 MX(s)

Write the corresponding equations:

Reactivity of Halogens with Halides

2 M+X-(aq) + X2(aq) 2 M+X-

(aq) + X2 (aq)

Cl2 (aq) + 2 Na+Br-(aq) 2 Na+Cl-

(aq) + Br2 (aq)

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

Br2 (aq) + 2 Na+I-(aq) 2 Na+Br-(aq) + I2 (aq)

F2 (aq) + 2 Na+Br-(aq) 2 Na+F-

(aq) + Br2 (aq)

F2 (aq) + 2 Na+Cl-(aq) 2 Na+F-

(aq) + Cl2 (aq)

F2 (aq) + 2 Na+I-(aq) 2 Na+F-

(aq) + I2 (aq)

Compare the reactions/reactivity with the position of the halogen / halide on the periodic table? What is the pattern?

Identifying halide ions

The presence of halide ions can be detected by reacting the salt with lead or silver salts… and observing the resulting precipitates. They have characteristic colors. (You did this in lab )

Ag+(aq) + X

(aq) AgX(s)

Write the equations to test for chloride, bromide, and iodide:

Group 8A Elements (ns2np6, n 2)

8.6

Completely filled ns and np subshells. Highest ionization energy of all elements.No tendency to accept extra electrons.

Properties of Oxides Across a Period(when added to water)

basic acidic

8.6

Reactions of Oxides of Period 3

Oxides of metals react with water to form a base

Na2O (s) + H2O (l) 2 Na+ (aq) + 2 OH1- (aq)

(NOTE: Mg(OH)2 is not very soluble.)

Write the corresponding equation for magnesium oxide

Reactions of Oxides of Period 3

Oxides of metals can act as a base to neutralize an acid to form salt and water.

MgO (s) + 2 HCl (aq) Mg2+ (aq) + 2 Cl1- (aq) + H2O (l)

Write the corresponding equation for sodium oxide:

Reactions of Oxides of Period 3Oxides of non metals react with water to form acids

CO2 (g) + H2O (l) H+ (aq) + 2 HCO31- (aq)

SiO2 (s) + H2O (l) not much of a reaction, however silicon dioxide will react as an acid to neutralize a base…

SiO2 (s) + 2 OH1- (aq) SiO3 2-

(s) + H2O (l)

P4O10 (s) + 6 H2O (l) 4 H+ (aq) + 4 H2PO41- (aq)

SO3 (s) + H2O (l) H+ (aq) + HSO41- (aq)

Properties of Chlorides Across a Period (when added to water)

neutral acidic

8.6

NaCl MgCl2AlCl3

(Al2Cl6 (g))SiCl4

PCl3PCl5

SCl2 Cl2

Type of bonding ionicgiant

covalentmolecular covalent

Structurecrystalline solid(extensive 3D

structure)solid liquid gas

Properties

high melting points

sublimes at 178°C to give vapor

low melting and boiling points

conduct electricity in molten and

(aq) states

molten chlorides do NOT conduct electricity (no ‘charged’ particles)

aqueous chlorides DO conduct electricity

Acid-Base Naturedissolve when added to water (neutral soln)

react with water to form acidic soln

Reactions of Chlorides of Period 3

NaCl (s) + H2O (l) Na+ (aq) + Cl- (aq) + H2O (l)

(No reaction, just dissolving)

(No reaction, just dissolving)

Write the corresponding equation for magnesium chloride

Reactions of Chlorides of Period 3AlCl3 (s) + 3 H2O (l) Al(OH)3 (s) + 3 H+ (aq) + 3 Cl- (aq)

SiCl4 (l) + 2 H2O (l) SiO2 (s) + 4 H+ (aq) + 4 Cl- (aq)

PCl3 (l) + 3 H2O (l) P(OH)3 (aq) + 3 H+ (aq) + 3 Cl- (aq)

[Note: P(OH)3 (aq) is also known as phosphoric(III) acid H3PO3, a weak acid ]

PCl5 (s) + 4 H2O (l) H3PO4 (aq) + 5 H+ (aq) + 5 Cl- (aq)

[Note: H3PO4 (aq) is known as phosphoric(V) acid, which is a strong acid ]

Cl2 (s) + H2O (l) H+ (aq) + Cl- (aq) + HOCl (aq)

[Note: HOCl (aq) is known as chloric acid and is a weak acid ]

What patterns do you notice?

Ready for Homework?

Exercise 3.3 p 80 # 1-10 due: __________

Exercise 13.1 p 84 # 1-5 due: __________

Suggestion –

• Work through the problems using the text and notes to answer the questions.

• Check your answers with the key.

• THEN, try to answer the problems again… without your notes.