Page 138 - Knowledge Organiser Yr9 24-25

Knowledge Base: Science C1: Atomic Structure and the Periodic Table Year 9
7. Relative Atomic Mass and Isotopes
7.1
What are isotopes?
Atoms of the same element with a different number of neutrons.
7.2
What is the relative atomic mass of an element?
An average value of mass that takes account of the abundance of the isotopes of the element.
7.3
What formula is used to calculate the relative atomic mass of an element?
7.4
Copper has two stable isotopes. Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30.8%. Calculate the relative atomic mass (Ar) of Copper to 1 decimal place.
9. Development of the Periodic Table
9.1
How were elements arranged in early versions of the periodic table?
In order of atomic weight.
9.2
Why were early versions of the periodic table not generally accepted?
They were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed.
9.3
Name two ways Mendeleev improved the early version of the periodic table.
• He placed the elements in groups based on similar properties.
• He left gaps for undiscovered elements.
• In some places he changed the order based
on atomic weights.
9.4
Copper has two stable isotopes. Cu-63 has an abundance of 69.2% and Cu-65 has an abundance of 30.8%. Calculate the relative atomic mass (Ar) of Copper to 1 decimal place.
• Mendeleev correctly predicted the properties of undiscovered elements.
• Discovery of isotopes confirmed he was right not to strictly order elements using their atomic weights.
8. The Periodic Table
8.1
How are elements in the periodic table arranged?
In order of atomic (proton) number.
8.2
What is a group in the periodic table?
A column of elements which have similar properties.
8.3
What is a period in the periodic table?
A row of elements.
8.4
Why is the periodic table so called?
Because similar properties occur at regular intervals.
8.5
What can the group number tell you about the electrons in an atom?
How many electrons are in the outer shell of the atom. E.g. carbon is in group 4 so has
4 electrons in the outer shell
8.6
What can the period tell you about the electrons in an atom?
How many shells an atom has.
E.g. carbon is in the second period
11. Group 0
11.1
What is the name of elements in group 0?
In order of atomic (proton) number.
11.2
Why are elements in group 0 unreactive?
Because their atoms have stable arrangements of electrons (they have full outer shells).
11.3
What is a period in the periodic table?
8.
11.4
Why is the periodic table so called?
The boiling point increases as you go down group 0.
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