Lesson 5: Isotopes/ RAM

Question 1

What are “isotopes”?

Answer 1

• Isotopes are atoms from the same element with the same number of protons but a different number of neutrons.

Question 2

What is the SAME in isotopes of the same element?

Answer 2

• Number of protons and electrons.
  They are the same element

Question 3

What is DIFFERENT in isotopes of the same element?

Answer 3

• Number of neutrons
  Mass number changed because of this

Question 4

There are two naturally occurring sulphur isotopes:
S³⁴ and S³²
Their atomic number is 16.
How many neutrons are there in each isotope?

Answer 4

S³⁴: 18 neutrons
S³²: 16 neutrons

Question 5

What is relative atomic mass?

Answer 5

• The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element.

Question 6

On the periodic table, how is the mass number determined?

Answer 6

• By working out an average (mean) of all the isotopes.

Question 7

What is the equation for relative atomic mass?

Answer 7

RAM = (%of isotope1x mass/ 100) + (%of isotope2 x mass/100)
If there is more than 2 isotopes, REPEAT AGAIN

Question 8

Why do you divide by 100 when calculating relative atomic mass?

Answer 8

• The abundance percenatge is out of 100 (as it is percentage.)
• So to calculate mean you need to divide by 100.

Question 9

Do isotopes of the same element have the same physical properties?

Answer 9

• No. Their boiling point changes because they are different masses.

Question 10

Do isotopes of the same element have the same chemical properties?

Answer 10

• Yes because electron arrangement is the same.

Question 11

How did the discovery of isotopes help validate Mendeleev’s periodic table?

Answer 11

• Some isotopes had different masses but the same chemical properties, so he was correct to put them in the same group.
• Rather than putting it in atomic weight order.