6.2 Group 7 Flashcards
What elements are in group 7?
The halogens
List the elements of group 7 in order (lightest to heaviest)
Fluorine (F)
Chlorine (Cl)
Bromine (Br)
Iodine (I)
Astatine (At)
HOw many electrons do group 7 elements have in their outer shell?
7
How do halogens exist in their natural state?
Diatomic molecules - pairs of atoms with a covalent bond (i.e. sharing a pair of electrons), e.g. Cl2, Br2
How do the melting and boiling points of halogens change as you go down the group?
Melting/boiling points increase as you go down the group
F and Cl are gases, Br is liquid, I is solid
Describe the properties of chlorine, bromine and iodine
Chlorine: reactive poisonous green gas
Bromine: poisonois red-borwn liquid, which gives off an orange vapour at room temperature
Iodine: poisonous dark grey crystalline solid, gives off a purple vapour when heated
How do you test for chlorine?
Bleaches damp litmus paper (turns from blue to white - but may transiently turn red forst as it is acidic in solution)
How does the reactivity of halogens change as you go down the group? Why?
They become LESS reactive as you go down the group
To react, they need to GAIN an electron, but as the outer shell gets farther from the nucleus, it become harder to attract the extra electron
Write a generic word equation to show the reaction of a group 7 element with a group 1 element
halogen + (group 1) metal —> metal halide
Write a balanced equation for chlorine reacting with sodium
CL2 + 2Na —> 2NaCl
Write a generic word equation to show the reaction of a group 7 element with hydrogen
halogen + hydrogen —> hydrogen halide
Write a balanced equation to show the reaction of chlorine with hydrogen
Cl2 + H2 —> 2HCl
What are the properties of hydrogen halides (give an example)
Soluble gases that dissolve in water to give an acidic solution
E.g. HCl gas dissolvded in water to give an aqueous solution of hydrochloric acid
What is the charge on a halide ion?
-1 (as it gains an electron to complete the outer shell)
