The Periodic Table

Question 1

How are elements in the modern periodic table arranged?

Answer 1

In order of atomic number and so that elements with similar properties are in the same group

the number of protons

Question 2

How were old periodic tables arragned?

Answer 2

In order of atomic weight

Question 3

How did Mendeleev in the mid-19th century create his version of the periodic table

Answer 3

1. He ordered the elements in order of increasing atomic weight , however he switched some elements if they had similar
   properties to elements in other groups
2. He realised that some elements had not been discovered yet and so he left gaps where he thought elements were missing
3. He predicted the properties of these undiscovered elemetns based off of the properties of other elements in the same group
4. Years later, the missing elements were discovered and their properties matched Mendeleev’s predictions

Question 4

Why didn’t Mendeleev order his periodic table in order of atomic number?

Answer 4

Protons were not discovered yet

Question 5

What is the** problem** with ordering the elemnts in order of their atomic weights?

Answer 5

Some elements can appear in the wwrong order due to the presence of isotopes (different number of neutrons)