The alkali metals

Question 1

Which group of elements are known as the alkali metals?

Answer 1

group 1

Question 2

Describe the properties of alkali metals relative to typical metals

Answer 2

similar:

• good conductors of heat and electricity
• shiny when freshly cut

different:

• soft (can be cut with a knife)
• relatively low melting points

Question 3

Describe how the alkali metals react with water

Answer 3

produce an alkaline metal hydroxide and hydrogen

(a hydroxide consists of hydrogen and oxygen, hydrogen molecules always consist of 2 atoms outside the hydroxide)

(e.g. sodium + water -> sodium hydroxide + hydrogen)

Question 4

Describe the reactivity of group 1 metals

Answer 4

• increases down the group
• lithium fizzes steadily in water and disappears
• sodium melts into a ball from the heat
• potassium melts, gives off sparks and produces hydrogen that burns with a lilac-coloured flame

(if universal indicator is used the water will go purple for all)

Question 5

Does the reactivity increase up or down the group?

Answer 5

down

Question 6

Describe the density of group 1 metals

Answer 6

lithium, sodium, and potassium less dense than water

this means they float

Question 7

Describe how group 1 metals are stored

Answer 7

lithium, sodium, potassium are stored in oil

this keeps water and air away

Question 8

Describe the properties of group 1 metals

Answer 8

• good conductors of heat/electric
• shiny when cut
• soft
• low melting points
• very reactive
• lose 1 electron when reacting

Question 9

Why does reactivity increase down the group?

Answer 9

• size increases down the group
• distance between the positive nucleus and outer electron increases
• the attractive force weakens
• becomes easier to lose the outer electron

Question 10

List the group 1 elements

Answer 10

lithium
sodium
potassium
ribidium
caesium
francium

Question 11

Rubidium is placed below potassium in the periodic table

Predict what is seen in the reaction of rubidium with water

Answer 11

rubidium will react very vigorously with water

produces sparks and bursts into flames explosively

Question 12

Explain why sodium is more reactive than lithium

Answer 12

• sodium atoms are larger than lithium atoms
• the outer electron is further from the nucleus in a sodium atoms than in a lithium atom
• the force of attraction in a lithium atom is weaker than a sodium atom
• the outer electron is lost easier from sodium than lithium

Question 13

Caesium, Cs, is placed below rubidium in group 1 of the periodic table.

Write a balanced equation for the reaction of caesium with water.

Answer 13

2Cs + 2H2O -> 2CsOH + H2

Question 14

Predict what is seen in the reaction of caesium with water.

Answer 14

• violent/very violent explosion
• sparks/flames
• hydrogen/bubbles produced
• metal disappearing

Question 15

State 2 physical properties that rubidium and caesium have in common

Answer 15

• good conductors of heat/electricity
• shiny when freshly cut
• soft
• relatively low melting points