EL.1

Question 1

What is the process in stars to generate energy and form heavier elements?

Answer 1

Nuclear fusion.

Question 2

What conditions are required for nuclear fusion to take place and why?

Answer 2

It requires high temperature and pressure so that the nuclei have high kinetic energy to overcome the electrostatic repulsion by positive charges on the two nuclei.

Question 3

How are element distributed throughout the universe?

Answer 3

Elements are scattered throughout the universe when a star becomes unstable and explodes in a supernova.

Question 4

What is the relative atomic mass of a proton?

Answer 4

1

Question 5

What is the relative atomic mass of a neutron?

Answer 5

1

Question 6

What is the relative atomic mass of an electron?

Answer 6

0.00055

Question 7

What is the charge of a proton?

Answer 7

+1/positive

Question 8

What is the charge of a neutron?

Answer 8

0/neutral

Question 9

What is the charge of an electron?

Answer 9

-1/negative

Question 10

Where is the proton found in an atom?

Answer 10

In the nucleus.

Question 11

Where is the neutron found in an atom?

Answer 11

In the nucleus.

Question 12

Where is the electron found in an atom?

Answer 12

Around the nucleus.

Question 13

Why are electrons so important?

Answer 13

Because they are the part that interact together with other atoms in a chemical reaction.

Question 14

What is the atomic number (Z)?

Answer 14

The atomic number (Z) is the number of protons in the nucleus. It is numerically equal to the number of electrons. The atomic number is the same for every atom of an element.

Question 15

What is the mass number (A)?

Answer 15

The mass number (A) is the number of protons and neutrons in the nucleus. Different atoms of the same element can have different mass numbers.

Question 16

How can we know how many neutrons there are in an atom?

Answer 16

Number of neutrons (N) = mass number (A) - atomic number (Z)

Question 17

What are isotopes?

Answer 17

Isotopes are atoms of the same element with different mass numbers. This is caused by different numbers of neutrons in the nucleus. Most elements exist naturally as a mixture of isotopes.

Question 18

What is relative atomic mass (Ar) ?

Answer 18

It is an average of the relative isotopic masses, calculated by taking into account of their abundances.

Question 19

What is the technique used to find the atomic mass of elements and compounds?

Answer 19

Mass spectrometry.

Question 20

How does mass spectrometry work?

Answer 20

In a mass spectrometer, sample atoms or molecules are ionised using a laser to become positively charged cations. These ions are then separated according to their mass m to charge z ratios, m/z. This is because the ions now have different masses and travel at different speeds. The separated ions are then detected by a detector and a relative abundance is counted.

Question 21

How can you calculate the relative abundance of an isotope from looking at a mass spectrometry graph?

Answer 21

Relative abundance = peek height / total peek heights

Question 22

How can you calculate the relative atomic mass of an atom?

Answer 22

Relative atomic mass = ((mass x abundance)+(mass x abundance)+…) / 100