Edexcel GCSE Chemistry - 1.2 The Periodic Table - 1.2.1 Mendeleev's Periodic Table

Sep 5, 2026

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Revision notes for Edexcel GCSE Chemistry covering section 1.2 The Periodic Table, focusing on subsection 1.2.1 Mendeleev’s Periodic Table. Explains why early scientists struggled to order elements, how periodic patterns emerged from sorting by mass, and how Mendeleev created his first draft using columns for properties and horizontal arrangement by increasing atomic mass. Describes his prediction method using gaps, including the eka-silicon idea and later confirmation, then addresses limitations such as isotopes and ordering issues solved in later developments.

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1.2 The Periodic Table

1.2.1 Mendeleev's Periodic Table

Mendeleev's Predictions

Problems with Mendeleev's Table

1.2.2 The Modern Periodic Table

Head to www.savemyexams. com for more awesome resources Edexcel GCSE Chemistry: Combined Science 1 .2 The Periodic Table Contents 1.2.1 Mendeleev ´s Periodic Table 1.2.2 The Modern Periodic Table 1.2.3 Electronic Con|gurations Page 1 of 12 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources 1.2.1 Mendeleev ´s Periodic Table Mendeleev's Arrangement Before the discovery of the subatomic particles, scientists struggled to |nd ways of ordering the growing knowledge of elements and their chemistry When the elements that were known at that time were sorted by mass into a table, patterns emerged at regular periods along the table, giving rise to the term periodic The earlier tables were incomplete as some elements were forced into a position to |ll gaps which appeared during the sorting process Other elements were placed in the wrong group as they were sorted strictly on their mass and had their chemical properties ignored There were many early versions of the tables as scientists in diyerent countries grappled with the ordering of the elements In 1869 the Russian chemist Dmitri Mendeleev created his |rst draft of the periodic table He organised the elements into vertical columns based on their properties and the properties of their compounds He then started to arrange them horizontally in order of increasing atomic mass and as he worked, he found that a pattern began to appear in which chemically similar elements fell naturally into the same columns Page 2 of 12 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Mendeleev 's Periodic Table showing gaps There were exceptions though as some elements didn 't |t the pattern when arranged by atomic mass Mendeleev worked to include all the elements, but he didn 't force an element to |t the pattern, rather he left gaps in the table that he thought would best be |lled by elements that had not yet been discovered He also switched the order of the elements to maintain consistency down the columns Page 3 of 12 © 2015 − 2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers Your notes Head to www.savemyexams. com for more awesome resources Mendeleev's Predictions Mendeleev quickly realised that elements with the same properties should be placed in the same column He realised that gaps in the table must correspond to elements that had not yet been discovered or isolated He used the properties and trends of other elements in the group with the gap to predict the properties of these undiscovered elements Mendeleev left a gap between silicon and tin and used his knowledge of the properties of those two elements to make predictions about the physical and chemical properties of the undiscovered element He called this element 'eka-silicon ' which comes from the Greek ' like silicon ' and when the element germanium was discovered in 1887 it was found to almost exactly match the properties Mendeleev had predicted No one doubted that Mendeleev had got the right idea about ordering the elements Strangely enough, Mendeleev always denied the existence of an eighth group of elements, even after the discovery of the noble gases in Mendeleev 's |nal years Examiner Tip Mendeleev’stable had gaps into which he didn’t force an element, rather he left them empty to be |lled at a later date when the correct element was isolated. In this way his version of the table allowed him to predict the existence and properties of then-unknown elements. Problems with Mendeleev's Table Once he was |nished, Mendeleev thought he had organised the elements systematically but there were still some elements which didn 't quite |t in as neatly as he wanted. This is because isotopes were not known in Mendeleev 's ti

FAQs

Why did scientists struggle to order the elements before subatomic particles were known?

Scientists had to find ways to sort the expanding knowledge of elements and their chemistry. Earlier tables were incomplete because some elements had to be placed to fill gaps, while others were in the wrong group when sorted strictly by mass.

How did Mendeleev arrange the elements in his Periodic Table?

He organised elements into vertical columns based on their properties and those of their compounds. Horizontally, he arranged them by increasing atomic mass and observed that chemically similar elements naturally fell into the same columns.

What did Mendeleev use his gaps for, and what evidence supported his predictions?

He left gaps for elements he thought would be discovered later, linking them to missing members of groups with established trends. His eka-silicon prediction was later matched closely when germanium was discovered in 1887.

Sep 5, 2026

Upload by Jacob