SC3 Atomic Structure

Question 1

How has the theory of the atom changed?

Answer 1

John Dalton’s theory = atoms as solid spheres
1897 J J Thomson = positive plum pudding with negative electrons inside
1909 Ernest Rutherford = conducted gold foil experiment resulting in nuclear atom theory - positive nucleus surrounded by cloud of electrons
Niels Bohr = electrons are in shells in fixed orbits around nucleus

Question 2

Subatomic particles charges

Answer 2

Proton = +1
Neutron = 0
Electron = -1

Question 3

Subatomic particles masses

Answer 3

Proton = 1
Neutron = 1
Electron = 0.0005

Question 4

Why do atoms have no overall charge?

Answer 4

They have the same number of electrons and protons

Question 5

Define atomic number

Answer 5

How many protons an atom has

Question 6

Define mass number

Answer 6

How many protons and neutrons an atom has

Question 7

Define isotope

Answer 7

different forms of the same element, which have the same number of protons, but different number of neutrons

Question 8

Calculate isotopic abundances

Answer 8

1) Multiply each relative isotopic mass by its isotopic abundance
2) Add up the results
3) Divide by the sum of the isotopic abundances

Question 9

Define relative atomic mass (Ar)

Answer 9

the average mass of one atom of the element, compared to 1/12 of the mass of one atom of carbon-12