SC1- Questions

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 scattered through a positively charged material.

Question 5

What did Ernest Rutherford discover from his gold foil experiment?

Answer 5

• Most of the particles passed straight through 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 (move around) 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 1x10-14 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

What does the atomic number of an atom represent?

Question 14

What does the mass number of an atom mean?

Answer 14

The mass number is the number 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

Fill in the blank:

‘Atoms of the same element have the same number of PROTONS in the nucleus and this is unique to that element’

Question 16

What is an isotope?

Answer 16

Isotopes 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 two values would be required to calculate the relative atomic mass of chlorine?

Answer 19

Mass numbers and relative abundances of all the isotopes of chlorine.

Question 20

How did Mendeleev arrange the elements in his periodic table?

Answer 20

Elements arranged with increasing atomic masses.
Elements with similar properties put into groups (due to periodic trends in chemical properties).
Switched the position of some elements.
Gaps left for undiscovered elements.

Question 21

How was Mendeleev able to predict the properties of new elements?

Answer 21

Mendeleev left gaps in his periodic table. He used the properties of elements next to these gaps to predict the properties of undiscovered elements.

Question 22

Mendeleev’s table lacked some amount of accuracy in the way he’d ordered his elements. Why was this?

Answer 22

Isotopes were poorly understood at the time.

Protons and neutrons had not yet been discovered.

Question 23

How are elements arranged in the modern periodic table?

Answer 23

In order of increasing atomic number.

Question 24

Fill in the blank:

‘Elements in the same group (column) have similar _______ ______’

Answer 24

Fill in the blank:

‘Elements in the same group (column) have similar CHEMICAL PROPERTIES’