topic 1.1 atomic structure

Question 1

how has the theory of atom’s structure changed throughout history

Answer 1

early 19th century john Dalton described atoms as solid spheres
1897 J.J Thompson’s plum pudding model
1909 Ernest Rutherford and his students did the golden foil experiment creating the NUCLEAR ATOM
Bohr model

Question 2

Describe the plum pudding model

Answer 2

JJ Thompson’s experiments found that atoms weren’t solid spheres.
Must contain smaller negatively charged particles.
“plums in a plum pudding”

Question 3

describe the golden foil experiment

Answer 3

Rutherford and his students in 1909 shot positive alpha particles in at an extremely thin sheet of gold.
expecting to pass straight through the sheet deflected MORE THAN EXPECTED and some straight BACKWARDS.
came up with nuclear model which had a cloud of negatively charged particles around the nucleus

Question 4

Describe the Bohr model of the atom

Answer 4

Realised that the cloud in the nuclear model would be attracted to the centre and collapse.
Bohr suggested electrons are in a fixed orbit or shells. and each shell have a fixed energy.

Question 5

what is the structure of the atom

Answer 5

A nucleus containing protons and neutrons surrounded by electrons in shells

Question 6

relative mass and charge of protons

Answer 6

mass= 1 charge = +1

Question 7

relative mass and charge of neutrons

Answer 7

mass= 1 charge =0

Question 8

relative mass and charge of electrons

Answer 8

mass= 0.0005 or 0 charge = -1

Question 9

why do atoms have equal electrons and protons

Answer 9

• as atoms are neutral
• as charges cancel out

Question 10

what is properties the nucleus

Answer 10

-middle of atom
- contains protons and neutrons
- positive charge
- mass concentrated in nucleus
- TINY compared to overall size of atom

Question 11

what is the mass number

Answer 11

-top number
- tells total number of protons and neutrons

Question 12

what is the atomic number

Answer 12

• bottom number
• how many protons an atom has
• work out same as elecrtons

Question 13

how to work out the number of neutrons in an atom

Answer 13

mass number - atomic number

Question 14

what are isotopes

Answer 14

different form of same element
same number of protons but a different number of neutrons

Question 15

why does isotopes mean that relative atomic masses of some elements not have a whole number

Answer 15

If an element has more than one isotope the average of mass numbers of all isotopes might not equal a whole number

Question 16

how do you calculate the relative atomic masses and abundance of isotopes

Answer 16

multiply the relative mass by its abundance.
divide by sum of abundances