Chaper 3- Aromic tructure

Question 1

What is Atomic number?

Answer 1

Number of protons in the nucleus of an atom of an element.

Question 2

What is Mass number?

Answer 2

Number of protons+ number of neutrons of an atom of an element.

Question 3

What is an isotope?

Answer 3

Atoms that contain the same number of protons but a different number of neutrons. They have a different mass number but the same atomic number.

Question 4

How are electrons arranged in an atom?

Answer 4

They are arranged in shells. Different shells have different energy levels (the further away the less the attraction).
The first shell can take 2 electrons and the second can take 8.

Question 5

What is the relative atomic mass, Ar?

Answer 5

Its calculated by the masses and the relative masses of all the isotopes.

Chlorine has two isotopes, chlorine -35 and chlorine-37.
A sample is 75% Cl-35 and 25% Cl-37
Mass 100 atoms= (75x35)+(25x37)=3550
Mass 1 atom= (3550/100)= 35.5 Ar- 35.5