Atoms

Question 1

What does the nucleus of an atom consist of?

Answer 1

protons and neutrons

Question 2

what is the third type of sub-atomic particle?

Answer 2

electrons

Question 3

where in relation to the nucleus are the electrons

Answer 3

they occupy a space outside the nucleus, orbiting in shells

Question 4

what is the charge and mass of: protons, neutrons and electrons?

Answer 4

Charge Mass
1+ 1
0 1
1- negligible

Question 5

what force holds electrons in place?

Answer 5

attractive electrostatic force

Question 6

define relative isotopic mass

Answer 6

the relative isotopic mass of an element is the mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12

Question 7

define relative atomic mass

Answer 7

relative atomic mass, Ar, is the weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon-12

Question 8

if in a species in chlorine 75% of atoms present were chlorine-35 and 25% of atoms were chlorine 37, what is the relative atomic mass of the species?

Answer 8

(75x35)+(25x37)/100 = 35.5(3s.f)

Question 9

what two things does the weighted mean mass take into account?

Answer 9

the percentage abundance of each isotope and the relative mass of each isotope

Question 10

define the term isotope

Answer 10

an isotope is an atom of the same element with the same number of electrons (and protons) but a different number of neutrons

Question 11

A sample of rubidium was analysed and found to be a mixture of two isotopes. It consists of 75% rubidium-85 and one other isotope. Define the mass number of the second isotope.

Answer 11

(75x85)+(__x25)/100 = 85.5 (as this is the mass number of rubidium)
85.5x100 = 8550
75x85 = 6375
8550-6375= 2175
2175/25 = 87