3 - Atomic Structure Flashcards
When did John Dalton publish his ideas about the atom?
1803
Describe how John Daltons idea of the atom looked like:
Solid ball
State some ideas in regards John Dalton’s atomic theory:
- Atoms cannot be broken down into anything simpler
- The atoms of a given element are identical to each other
- The atoms of different elements are different from one another
- During chemical reactions atoms rearrange to make different substances
What did Daltons theory help to explain?
The properties of matter
What is the relative charge of a Proton?
+1
When was the electron discovered? And by who?
In 1897 by JJ Thompson
What model did JJ Thompson propose?
Plum pudding model
Describe how the plum pudding model looked like:
An atom is a sphere of positive charge, with negatively charged electrons scattered in it
Explain how Ernest Rutherford discovered the nuclear atom:
He did the gold foil experiment.
He directed a beam of alpha particles at a very thin gold foil in a vacuum
What observations did Rutherford see during the gold foil experiment?
- Most alpha particles went straight through
- A small number of alpha particles were being deflected at large angles
- There were a very small number of alpha particles coming straight back
What does a small number of alpha particles were deflected @ large angles show in the gold foil experiment?
There is a concentration of positive charge in the atom
What does a small number of alpha particles were coming straight back show in the gold foil experiment?
The positive charge and mass are concentrated in a tiny volume in the atom (the nucleus)
What does most of the alpha particles going straight through show in the gold foil experiment?
Evidence for the atom being mostly empty space
Why is it important that Rutherford conducted the gold foil experiment in a Vacuum?
So any deflection of the alpha particles would only be because of collisions with the gold foil.
And not due to deflections off anything else
Who confirmed that the rearranged order of elements is correct?
Henry Moseley
Describe the structure of an atom:
A nucleus containing protons and neutrons, surrounded by electrons in shells
What is the relative charge of a Proton?
+1
What is the relative charge of a Electron?
-1
What is the relative charge of a Neutron?
0
What is the relative mass of a Proton?
1
What is the relative mass of a Electron?
1/2000
or
1/1835
What is the relative mass of a Neutron?
1
Where is most of the mass in an atom concentrated?
The Nucleus
What does the term Mass number mean?
The total number of protons and electrons in the nucleus of an atom
What do we measure the mass of atoms relative to?
An atom of carbon 12
What’s the relative mass of Helium-4?
4
What’s the relative mass of magnesium?
24
What does the term Isotopes mean?
Different atoms of the same element containing the same number of protons but different numbers of neutrons in their nuclei
Describe the size of the nucleus of the atom:
Very small compared to the overall size of the atom
What is an atomic number?
The number of protons in the nucleus of an atom
What is the atomic number also known as?
Proton number
Label which is the following:
- Mass number
- Atom symbol
- Atomic number
What is Nuclear fission?
When the nucleus of a large atom splits into 2 smaller nuclei
What is Relative atomic mass?
The mean mass of an atom of an element compared with Carbon-12
What does RAM stand for?
Relative atomic mass
What does RAM take into account?
All the isotopes of the element + amounts of each
How do you calculate RAM using relative masses and the abundances of its isotopes?
Calculate the RAM of an element:
Why does the existence of isotopes results in relative atomic masses of some elements not being whole numbers?
RAM is the MEAN mass of an atom. It takes into account all the isotopes of the elements + amounts
Therefore, RAMs are not whole numbers, most values are commonly rounded to whole numbers
What is mass number?
The total number of protons and neutrons
Where is most of the mass in an atom concentrated in?
The Nucleus
Explain why atoms are neutral?
They always have the same number of protons and electrons —> Charges cancel out
