U6 - Group periods

Question 1

Properties of Alkali metals

Answer 1

• Shiny, malleable, ductile, sonorous, good conductors
• Relatively soft metals
• Newly cut surfaces are silvery shiny for a short period of time
• Very reactive – stored under oil to prevent reaction with oxygen and water
• Low melting points
• Low densities – some float on water
• Form white water soluble salts

Question 2

Reaction of alkali metals with water

Answer 2

Water + alkali metal —— alkali sol. + hydrogen gas

Question 3

What happen when alkali metals react with oxygen

Answer 3

burns forming a white solid

Question 4

What happens when alkali metals react with Cl when heated

Answer 4

forms a white salt

Question 5

Explain the flame test for group 1 metals:

Answer 5

A clean platinum wire is dipped into some hydrochloric acid, and then
dipped into a salt sample of the substance.
The tip of the platinum wire is then held in the flame of a Bunsen burner
The colour of the flame produced is an indication of which metal is present in the salt.

Question 6

What colour flame does lithium, sodium and potassium produce

Answer 6

L - Red
S - Orange
P - Lilac

Question 7

Properties of alkali earth metals

Answer 7

• not as soft or reactive as gr 1
• 2 outer shell electrons
• Form 2+ ions
• Form white salts that are slightly soluble in water

Question 8

Test for hydrogen

Answer 8

burning splint, popping /whistling sound, burns with a blue flame

Question 9

Group 2 elements react with water

Answer 9

Mg: reacts slowly with cold water (forming a few bubbles of hydrogen) but vigorously with steam
Ca: Reacts rapidly with water forming hydrogen gas

Question 10

Properties of group 7 elements

Answer 10

• Halogens
• Diatomic non-metals
• 7 electrons in outer shell
• Form 1- ions by gaining one electron to fill the shell

Question 11

What happens to the reactivity when you go down gr 7 element

Answer 11

• Colour becomes darker:
  Fluorine – Yellow
  Chlorine - green
  Bromine - red/brown
  Iodine - purple/black
• iodine crystals are purple-black, but when iodine is
  dissolved in alcohol or water it is red-brown in colour
• Reactivity decreases
• Melting and boiling point increase – phase changes from gas to liquid to solid as you move down the group

Question 12

Chemical reactions with other halide ions

Answer 12

Halogens undergo displacement reactions.
The more reactive halogen will displace a less reactive halide from its salt

Question 13

Properties of transition metals

Answer 13

• Not ordered into groups
• Also known as heavy metals
  *General metallic properties: malleable; ductile; sonorous; good conductors
• High melting and boiling points
• High densities
• More than one valency/oxidation state. i.e Cu+ or Cu2+
  Fe2+ or Fe3+
• Form coloured compounds
• Used as catalysts in industrial processes

Question 14

What are valence electrons

Answer 14

Valency refers to the number of bonding places an element has.

Question 15

Properties of noble gasses

Answer 15

• Unreactive – filled outer shells
• Gases; non-metals
• Going down the group: melting and boiling points increase
• Density increases
• Used where an inert atmosphere is needed