Page 66 - Science Coursebook
P. 66
4.3 Trends in Group 1
Groups in the Periodic Table
In Stage 8 you learnt that the columns
in the Periodic Table are called groups. Group 1
The first group, also known as the alkali (alkali metals)
metals, includes the elements lithium,
sodium and potassium. These elements Li
have some properties in common.
Na
The table below contains data about K
three of the metals in Group 1.
Element Atomic number Mass number Melting point / °C Boiling point / °C
lithium, Li 3 7 180 1360
sodium, Na 11 23 98 900
potassium, K 19 39 63 777
As you can see, the atomic number increases as you go down the group. The mass
number also increases as you go down the group. These increasing numbers show you
that the size of the atom is increasing.
When you look at the melting points you can see that they go down as you go down
the group. The next metal down in the group is rubidium. We can predict it would
have a melting point lower than 63 °C.
Questions
1 Where in the Periodic Table do you find the metals?
2 What is the trend shown in the boiling points of Group 1 elements?
A+I 3 What prediction can you make about the boiling point of rubidium?
4 How many more electrons than lithium does an atom of sodium have?
Activity 4.3
Reactions in Group 1 metals
SE Your teacher will demonstrate the reactions of lithium, sodium and potassium
with water. The three elements are stored in a particular way and your teacher
will cut a small piece of the metal to react in a trough (bowl) of water. Watch
carefully and record your observations.
Questions
A1 Describe the safety precautions your teacher took.
A2 Describe what you saw happen when each of the metals reacted with the water.
A3 Write the word equation for each reaction.
A4 What similarities do you notice about the reactions of these metals?
A5 What differences do you notice about the reactions of these metals?
A6 List the properties that these elements share.
A7 Suggest why the next element in this group, rubidium, is not used in schools.
64 4 Material properties
A+E
