Topic 1 - Atomic Structure

Question 1

What are the three ideas in John Dalton’s theory about the atom?

Answer 1

• Atoms cannot be created, divided or destroyed.
• Atoms of the same element are exactly the same and atoms of different elements are different.
• Atoms join with other atoms to make new substances

Question 2

What discovery caused the original Dalton model of an atom to change?

Answer 2

The discovery of subatomic particles.

Question 3

How did JJ Thomson discover the electron?

Answer 3

• Thomson experimented with a cathode ray tube.
• The beam moved towards the positively charged plate so he knew that the particles must have a negative charge.

Question 4

Describe the atomic model proposed by JJ Thomson

Answer 4

• Plum pudding model
• Negatively charged electrons scatterd through a positively charged material

Question 5

What did Ernest Rutherford discover from his gold foil experiment?

Answer 5

He shot a beam of positievely charged particles at sheet of gold foil:

• Most of the particles passed straight throuhg suggesting that atoms were mostly empty space.
• A few particles were deflected and a few bounced directly back showing that there must be a tiny, dense and positively-charged nucleus

Question 6

Describe Rutherford’s new model of the atom

Answer 6

• Mass is concentrated in the central nucleus
• Mostly empty space.
• Electrons travel in random paths around the nucleus

Question 7

Describe the structure of an atom

Answer 7

• Small central nucleus made up of protons and neutrons.
• Electrons orbit the nucleus in shells

Question 8

What is the radius of the nucleus? How large is it compared to the radius atom?

Answer 8

• The radius of the nucleus is 1 x 10^-14 m.
• This is 1/10000 of the atomic radius.

Question 9

What are the relative masses of protons, neutrons and electrons?

Answer 9

Proton: 1

Neutron: 1

Electron: 1/1836

Question 10

What are the relative charges of protons neutrons and electrons?

Answer 10

Proton: +1

Neutron: 0

Electron: -1

Question 11

Why do atoms contain equal numbers of protons and electrons?

Answer 11

• Atoms are stable with no overall charge
• Protons are positively charged and electrons are negatively charged. For the charges to balance, the number of protons and electrons must be equal

Question 12

Where is the mass of an atom concentrated?

Answer 12

• In the nucleus

Question 13

What does the atomic number of an atom represent?

Answer 13

• The number of protons

Question 14

What does the mass number number of an atom mean?

Answer 14

• The mass number is the of protons and neutrons found in the nucleus of an atom

Question 15

Fill in the blank: ‘ Atoms of the same element have the same number of—— in the nucleus and this is unique to that element’

Answer 15

Protons

Question 16

What is an isotope?

Answer 16

Isotopes of an element are atoms with the same number of protons(so they are the same element) but a different number of neutrons.

Isotopes of an element have the same atomic number but different mass numbers.

Question 17

Boron has the atomic number 5 and the mass number 11. How many protons, electrons and neutrons does Boron have?

Answer 17

5 protons

5 electrons

6 neutrons

Question 18

Why is the relative atomic mass not always a whole number?

Answer 18

• Different isotopes of the same element have different mass numbers. The relative atomic mass is an average of the masses of all these isotopes

Question 19

What is the formula for calculating the relative masses and abundance’s of its isotopes?

Answer 19

it is a ‘+’ not division sign

Question 20

What is the order for the valency table?

Answer 20