4.4 Group 17 Elements

Physical properties
■ Elements of Group 17 also known as halogens

	►	Flourine, F Chlorine, Cl Bromine, Br Iodine, I Astatine, At
	►	The following mnemonic method can be used to memorize the sequence of elements in Group 17. ○ Fairy Clowns Broil Innocent Ants.

■ Physical properties of halogens

	►	Elements Proton number Atomic radius (nm) Melting point (℃) Boiling point (℃) Density (gcm-3) Color Flourine, Fl 9 0.06 -220 -187 1.12 Light yellow Chlorine, Cl 17 0.10 -102 -34 1.57 Greenish yellow Bromine, Br 35 0.12 -7.2 59 3.13 Reddish-brown Iodine, I 53 0.14 114 183 4.95 Purple-black
	►	Low melting points and boiling point. ○ All halogens exist as diatomic molecules gas (F2, Cl2, Br2, I2, At2)
	►	Do not conduct electricity
	►	Weak conductors of heat
	►	Low density
	►	The animation below shows the changes in physical properties of Group 17 elements down the group.

Chemical properties
■ Arrangement of electron in halogen elements.

Element Electron configuration Arrangement of electron Flourine 2.7 Chlorine 2.8.7 Bromine 2.8.18.7 Iodine 2.8.18.18.7 Astatine 2.8.18.32.18.7

■ Chemical reaction.

	►	Alkali halogens elements show similar properties when reacting with certain compounds. ○ Halogens react with water to form two acid. Laboratory Activity 4.4.1: Studying the reaction of chlorine, bromine and iodine with water ○ Halogens react with hot iron to form a brown solid, iron (II) halides. Laboratory Activity 4.4.2: Studying the reaction of halogens with iron wool ○ Halogens react with sodium hydroxide solution to form sodium halide, sodium halate (I) and water. Laboratory Activity 4.4.3: Studying the reaction of halogens with aqueous sodium hydroxide solution
	►	Brief explanation on the reaction of halogen. ○ All halogens have 7 valence electron. ○ They receive an electron to form an anion or negative ion in order to attain the stable octet or noble gas electron arrangement.
	►	The reactivity of halogens decreases as down the group.
	►	The animation below shows the explanation on the changes on the reactivity of alkali metals.

■ This video contains information about the physical properties and the reactions of the Group 17 elements.

← 4.3 Group 1 Elements

4.5 Elements in Period →

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