C2.3 Atomic structure etc.

Question 1

What is the mass number of an atom?

Answer 1

The total number of protons and neutrons

Question 2

What is an isotope?

Answer 2

Isotopes are atoms of the same element that have different mass numbers but the same atomic number

Question 3

What symbol represents relative atomic mass?

Answer 3

Ar

The mass of the particular ATOM
eg K, Na, Rb

Question 4

What symbol represents relative formula mass?

Answer 4

Mr

The mass of the whole molecule
eg H7C13 would be 7 x Ar of H plus 13 x Ar of C

Question 5

What is one mole of a substance?

Answer 5

One mole is the Mr / Ar of a substance shown in grams

Question 6

If one mole of Carbon monoxide is 28g, how many moles are in

• 56g of carbon monoxide
• 14g of carbon monoxide

Answer 6

56 / 28 = 2
2 moles

14/28 = 0.5
0.5 moles

Question 7

Why is the Ar for some elements not a whole number (eg chlorine = 35.5)?

Answer 7

The Ar is the average atomic mass from all the isotopes of the element

Question 8

How would you calculate the Ar of Chlorine where 75% have an Ar of 35 and 25% have an Ar of 37?

Answer 8

In 100 atoms of chlorine:
75 would be 35
25 would be 37

Find the mean average: 
75 x 35 = 2625
25 x 37 = 925
2625 + 925 = 3550
3550 / 100 = 35.5

Question 9

What is the ‘standard atom’ that other atoms are relative to?

Answer 9

Carbon (Ar 12)

Question 10

What part of the element stays the same in its isotopes?

Answer 10

The proton number / atomic number