SC4 Periodic Table

Question 1

SC4a
1) Describe how Mendeleev arranged elements into a periodic table
2) Describe how Mendeleev predicted the existence and properties of some elements yet to be discovered.
3) Explain how Mendeleev’s early ideas were supported by later evidence

Answer 1

1) The table was ordered by increasing atomic mass.
2) Mendeleev left some gaps in order to keep elements with similar properties in the same group.
3) Mendeleev predicted the existence of ‘eka-silicon’, which would fit into a gap next to silicon. The element germanium was discovered later. Its properties were found to be similar to the predicted ones and confirmed Mendeleev’s periodic table.

Question 2

SC4b
1) Explain some problems Mendeleev had when ordering the elements
2) Explain the meaning of the term ‘atomic number’
3) Describe how the elements are arranged in the modern periodic table
4) State the positions of metals and non-metals in the periodic table

Answer 2

1) Mendeleev had to leave gaps as some elements were not discovered yet. Also, elements were not in the same group as with elements that had similar properties, so he swapped them around.
2) The atomic number is the number of protons in an atom.
3) Elements are arranged by increasing atomic number.
4) The metals are to the left of the line (except for hydrogen, which is a non-metal), the non-metals are on the right.

Question 3

SC4c
1) State what the term ‘electronic configuration’ means
2) How would an electronic configuration in the form 2.8.1 be drawn on a diagrams?
3) Explain the links between an element’s position in the periodic table and its electronic configuration

Answer 3

1) An atom’s electronic configuration is the way an atom’s electrons are arranged.
2) There would be 3 electrons shells (drawn as circles) with the electrons drawn on as dots or crosses. There would be 2 on the first (inner) shell, 8 on the second shell, and 1 on the third (outer) shell.
3) The number of occupied shells is equal to the period number. The number of electrons in the outer shell is equal to the group number. All the shells apart from the outer shell will be filled.

Question 4

SC4c
1) How many electrons can fit on the first three shells?
2) How are electronic configutations written?

Answer 4

1) 2 on the first, 8 on the second, and 8 on the third.
2) The numbers show how many electrons occupy a shell, and the commas/full stops separate each shell.