U1.2: The Nuclear Atom Flashcards
Define atomic number
The number of protons in the nucleus of an aotm
Define atomic mass number
The number of protons + neutrons in an atom
Define relative atomic mass
the average mass of all the isotopes of an element relative to 1/12th of the mass of Carbon-12 atom
Define atomic mass units (AMU)
Used to express the masses of atomic particles
Formula for relative atomic mass
[Isotope 1(%1) + Isotope 2(%2) +…. ] / 100
Formula for relative abundance
one of the isotopes is x, the other is 100-x
- Atomic mass of isotope1(x) + atomic mass of isotope2(100-x) ALL DIVIDED BY 100 = Mr of element
- solve for x (which is the abundance of one of the isotopes) then find 100-x (which is the abundance of the other isotope)
Define isotopes
Isotopes contain the same number of protons but a different number of neutrons of the same element
What properties of isotopes are different
The physical properties:
- Density
- Rate of diffusion
- Boiling point
What is the trend of isotopes?
Similar chemical properties, different physical properties although they all react the same way
What is the mass spectrometer
It’s used to determine the relative atomic mass of gaseous elements and can also show isotopic composition
What elements go through the mass spectrometer faster?
Lighter elements
How to find mass lost on fragmentation pattern
Furthest peak subtracted with the next peak to obtain a value of which is the mass lost. That shows the fragment lost
What do the peaks show on the fragmentation pattern
Peaks show the relative abundances of the number of isotopes present
What does the height of each peak indicate
The relative abundance of the respective isotope
How to find relative molecular mass when given a mass spectrum?
Look for molecular ion peak to find abundance and read m/z ratio to find Mr
- use formula: m1(%abundance) +… /100
Compare the chemical properties of all isotopes and justify your reasoning
Chemical properties of all isotopes are similar because they have the same number of electrons; It’s the electrons that are responsible for chemical properties
Why would the RAM of one element be greater than the RAM of another’s even if the Ar of the second element’s greater than the Ar of the first?
The RAM would be greater due to greater number of neutrons in one element compared to the other
Does the chloride ion or chlorine atom have a larger radius? Justify your reasoning
Cl ion has a larger radius due to more electron-electron repulsion
In terms of isotopes. what does 1:1 ratio mean
The average of the 2 mass numbers given
What is affected when an element has an isotope of fewer neutrons in its atom
The isotope has a lower density
Define relative abundance
Relative abundance is the percent abundance in nature of a particular isotope
How to find relative molecular mass of an element using mass spectrum
- Determine if it is a diatomic molecule or not; if yes, multiply Mr by 2 and only look at peaks on or past that point
- m/z(relative intensity) + 2nd m/z(2nd relative intensity) +… ALL DIVIDED BY RELATIVE INTENSITIES MULTIPLIED WITH ADDED UP
in a mass spectrum of chlorine gas, what particle causes the peak at 35 m/z. Also, why does it have the charge it has
Cl-35 +
- This has a positive charge as the peak is from a single atom of Cl-35 that has been bombarded with electrons in the mass spectrometer resulting in the positively charged particle
