3.1.1 Atomic Structure Flashcards
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
1/2000
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of an electron?
-1
Mass number [definition]:
The total number of protons and neutrons in the nucleus of an atom
Atomic number [definition]:
The number of protons in the nucleus of an atom
Ion [definition]:
A charged particle formed when one or more electrons are lost or gained by an atom or molecule
Ions [2]:
- Negative ions have more electrons than protons
- Positive ions have more protons than electrons
Isotope [definition]:
An atom with the same number of protons but a different number of neutrons
Calculating Ion Charge:
Ion Charge = number of protons - number of electrons
Overall charge [2]:
- The overall charge of any chemical substance will be zero.
- So cations will always be accompanied by anions in solid or in solution.
The relative atomic mass of an isotope (abundance):
. 100
John Dalton’s atomic model [4]:
- 19th century
- He described atoms as solid spheres
- He said that these solid spheres that made up different atoms
- He believed that atoms were a fundamental unit of matter and were indivisible
J.J Thompson’s model of the atom (plum pudding)
[3]:
- In 1897 he concluded that atoms must contain even smaller atoms (electrons)
- He discovered that atoms were divisible
- He viewed the atom as a large positively charged sphere with embedded, smaller, negatively charged electrons
When was the golden foil experiment conducted and by whom?
In 1909, Ernest Rutherford and his students Hans Geiger and Ernest Marsden conducted the gold foil experiment
The Gold foil experiment [2]:
- Ernest Rutherford and his students fired positively charged alpha particles at a very thin sheet of gold
- Rutherford believed that electrons were in a cloud around the nucleus of an atom
What did the gold foil experiment mean? [3]:
- Most of the alpha particles went through the gold which indicated that there is empty space in an atom
- A few particles were deflected suggesting that there is a positive mass in the centre of the atoms
- This disproved the plum pudding model as if it were true all the particles would’ve been deflected by the gold
What did Scientists realise about Rutherford’s cloud of electrons?
Electrons in a cloud around the nucleus would quickly spiral down into the nucleus and collapse
Bohr’s atomic model [4]:
- Electrons only exist in fixed orbits
- Each shell has a fixed energy
- When an electron moves between shells, electromagnetic radiation is emitted or absorbed
- Due to the energy of shells being fixed the radiation will have a fixed frequency