Group 17

Group 17

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Content

● Periodicity of atomic and physical properties of the elements: variation with proton number across the third period (sodium to chlorine) and down the group (Group 2 and Group 17) of:

(i) electronic configuration

(ii) atomic radius and ionic radius

(iii) ionisation energy

(iv) electronegativity

(v) melting point

(vi) electrical conductivity

• Periodicity of chemical properties of the elements in the third period:

(i) variation in oxidation number and bonding of the oxides (sodium to sulfur only) and of the chlorides (sodium to phosphorus only)

(ii) reactions of these oxides and chlorides with water

(iii) acid/base behaviour of these oxides and the corresponding hydroxides

• Periodicity of chemical properties of the elements down the group (Group 2 and Group 17):

(i) as reducing agents (Group 2) and oxidising agents (Group 17)

(ii) thermal stability of Group 2 carbonates and Group 17 hydrides

Learning Outcomes

Trends and variations in atomic and physical properties

For elements in the third period (sodium to chlorine), and in Group 2 (magnesium to barium) and Group 17 (chlorine to iodine) candidates should be able to:

(a) recognise variation in the electronic configurations across a Period and down a Group

(b) describe and explain qualitatively the general trends and variations in atomic radius, ionic radius, first ionisation energy and electronegativity:

(i) across a Period in terms of shielding and nuclear charge

(ii) down a Group in terms of increasing number of electronic shells, shielding and nuclear charge

(c) interpret the variation in melting point and in electrical conductivity across a Period in terms of structure and bonding in the elements (metallic, giant molecular, or simple molecular)

(d) describe and explain the trend in volatility of the Group 17 elements in terms of instantaneous dipoleinduced dipole attraction

Trends and variations in chemical properties

For elements in the third period (sodium to chlorine) candidates should be able to:

(e) (i) state and explain the variation in the highest oxidation number of the elements in oxides (for Na2 O;

MgO; Al2 O3 ; SiO2 ; P4 O10 ; SO3 ) and chlorides (for NaCl; MgCl2 ; AlCl3 ; SiCl4 ; PCl5 )

(ii) state and explain the variation in bonding in oxides and chlorides in terms of electronegativity (with the exception of AlCl3 )

(iii) describe the reactions of the oxides with water (for Na2 O; MgO; Al2 O3 ; SiO2 ; P4 O10 ; SO3 )

(iv) describe and explain the acid/base behaviour of oxides (for Na2 O; MgO; Al2 O3 ; SiO2 ; P4 O10 ; SO3 ) and hydroxides (for NaOH; Mg(OH)2 ; Al(OH)3 ), including, where relevant, amphoteric behaviour in reaction with sodium hydroxide (only) and acids

(v) describe and explain the reactions of the chlorides with water (for NaCl; MgCl2 ; AlCl3 ; SiCl4 ; PCl5 )

(vi) suggest the types of structure and bonding present in the oxides and chlorides from observations of their chemical and physical properties

For elements in Group 2 (magnesium to barium) and Group 17 (chlorine to iodine) candidates should be able to:

(f) describe and deduce from E ⦵ values the relative reactivity of elements of:

(i) Group 2 as reducing agents

(ii) Group 17 as oxidising agents

(g) describe and explain the trend in thermal stability of:

(i) Group 2 carbonates in terms of the charge density of the cation and the polarisability of the large anion

(ii) Group 17 hydrides in terms of bond energies

In addition, candidates should be able to:

(h) predict the characteristic properties of an element in a given Group by using knowledge of chemical periodicity

(i) deduce the nature, possible position in the Periodic Table, and identity of unknown elements from given information of physical and chemical properties