Chemistry Reference
In-Depth Information
Potassium is more reactive because less energy is
required to remove the outer electron from its atom
than for lithium or sodium. This is because as you go
down the group the size of the atoms increases and
the outer electron gets further away from the nucleus
and becomes easier to remove.
e
Questions
1
Write word and balanced chemical equations for the
reactions between:
a
sodium and oxygen
b
sodium and water.
2
Using the information on pp. 138-140, predict the properties
of the element francium related to its melting point, density
and softness. Predict how francium would react with water
and write a balanced equation for the reaction.
3
Write word and balanced chemical equations for the
reactions between:
a
magnesium and water
b
calcium and oxygen.
4
Account for the fact that calcium is more reactive than
magnesium.
sodium atom
(Na)
sodium ion
(Na
)
Na
e
Na
Figure 9.9
This sodium atom loses an electron to become a sodium ion.
Look at Figure 9.10. Why do you think potassium is
more reactive than lithium or sodium?
3
Li
3p
4n
●
Group II - the alkaline
earth metals
Group II consists of the fi ve metals beryllium,
magnesium, calcium, strontium and barium, and
the radioactive element radium. Magnesium and
calcium are generally available for use in school.
These metals have the following properties.
●
They are harder than those in Group I.
●
They are silvery-grey in colour when pure and
clean. They tarnish quickly, however, when left in
air due to the formation of a metal oxide on their
surfaces (Figure 9.11).
2,1
2
11
Na
11p
12n
2,8,1
3
19
K
19p
20n
2,8,8,1
Figure 9.11
Tarnished (left) and cleaned-up magnesium.
Figure 9.10
Electronic structures of lithium, sodium and potassium.
