Chemistrey Revision For Assessment

Question 1

Why is the relative atomic mass of many elements not a whole number?

Answer 1

Relative atomic masses are weighted average of the mass number of different isotopes and abundance of that element

Question 2

What are the changes of the Dalton model to today’s modern model

Answer 2

Subatomic particles

Question 3

What is a mass number of an atom

Answer 3

The total number of protons and neutrons in the nucleus of an atom

Question 4

What are Isotopes?

Answer 4

Isotopes are different variations of an element which have the same number of protons but different numbers of neutrons, they differ in relative atomic mass and abundance (but not in chemical properties)

Question 5

What was unique about Mendeleev’s model periodic table and what has changed to now of it?

Answer 5

His period table was organised in rows and columns. He used to organise the elements by the atomic mass number but now it’s organised by atomic number

Question 6

Describe how Mendeleev arranged the elements?

Answer 6

By the elements atomic mass number in rows and columns

Question 7

How did Mendeleev predict the existence of properties and elements?

Answer 7

He left gaps in his period table. By looking at the physical and chemical properties of some elements next to a gap

Question 8

Explain why Mendeleev is wrong in arranging the elements in order of increasing relative atomic mass

Answer 8

Because it’s inaccurate since some elements of isotopes differed in abundance and mass