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
What is the top number on the periodic table?
Mass number
What is the bottom number on the periodic table?
Atomic number
What is the mass number?
Total number of protons and neutrons.
What is the atomic number?
Number of protons (and therefore electrons).
Do negative ions have more protons or electrons?
More electrons
What is an isotope?
An atom with the same number of protons but different number of neutrons.
Do isotopes have the same chemical properties?
Yes
What affects chemical properties?
Configuration of electrons.
What affects physical properties?
Mass
Do isotopes have the same physical properties?
No
What did John Dalton discover about the atom?
*atoms are spheres
*each element is made from different spheres
What did J.J.Thompson discover about the atom?
*discovered electrons
*came up with the plum pudding model
*the atom isn’t solid
What is the plum pudding model?
The atom is made up of a positive ‘pudding’ and negative ‘plum’ electrons.
What did Ernest Rutherford discover about the atom?
*discovered small and positively charged nucleus
*atom is mainly empty space
*negative electron cloud
Explain Rutherford’s gold leaf experiment.
*positive alpha particles fired at thin gold leaf
*most went through (mainly empty space)
*small amount were deflected back (hit small positive nucleus)
What did Neils Bohr discover about the atom?
*electrons were in fixed shells
What did Neils Bohr think was the problem with Rutherford’s atomic model?
The negative electron cloud would collapse into the positive nucleus.
Describe Neils Bohr’s experiement.
*EM radiation was absorbed by electrons causing them to move between shells
*electrons emit this radiation when they move to lower energy levels
What was the order of discoveries about the atom?
*John Dalton - 1803
*J.J.Thompson - 1897
*Ernest Rutherford - 1909
*Neils Bohr - 1913
What is different now about the atomic structure to Bohr’s model?
Not all electrons in the same shell have the same energy, therefore there are sub-shells.
What are the four steps involved in time of flight mass spectrometry?
- ionisation
- acceleration
- ion drift
- detection
What are the 2 ways of ionising a sample?
*electrospray ionisation
*electron impact ionsiation
Describe electrospray ionisation.
*sample is dissolved and pushed through nozzel at high pressure - turns into gas
*high voltage is applied to sample - each particle gains a H+ ion
Describe electron impact ionisation.
*sample is vaporised
*electron gun fires high energy electrons at it
*one electron is knocked off each particle - forming 1+ ions
Describe acceleration in mass spectrometry.
Ions are accelerated by an electric field to give them all the same kinetic energy.
Describe ion drift in mass spectrometry.
*ions enter a region with no electric field
*lighter ions drift faster than heavy ones
Describe detection in mass spectrometry.
*lighter ions reach the detector first
*when charged particles hit the detector they produce an electrical current
*mass spectrum is produced
Define relative atomic mass.
The average mass of an atom of an element when measured on a scale on which the mass of C12 is exactly 12.
What is the symbol for atomic mass?
Ar
Define relative molecular mass.
The average mass of a molecule when measured on a scale on which the mass of C12 is exactly 12.
Define relative isotopic mass.
The mass of an atom of an isotope of an element when measured on a scale on which the mass of C12 is exactly 12.
