2.1- Atoms and reactions

Mass of proton

1

Mass of a neutron

1

Mass of an electron

1/1836

What holds an atom together?

The electrostatic attraction between the positively charged nucleus and the negatively charged electrons orbiting around.

Isotope

Atoms of the same element that contain the same number of protons and electrons but a different number of neutrons

What is different between isotopes

Different physical properties such as mass and density

Standard unit for atomic mass

u

What is the standard atomic mass for comparison

The mass of 1/12th of a carbon 12 atom

Mass of carbon 12 atom

12u

Relative isotopic mass

The mass of an atom of an isotope relative to 1/12th the masss of an isotope relative to 1/12th mass of a carbon-12 atom

Relative atomic mass

The average mass of an atom relative to 1/12th of the mass of a carbon-12 atom.

How can the percentage abundance of an isotope be found?

Using a mass spectrometer

How are mass spectra interpreted?

Assuming all ions are singly charged (+1)

Mass spectrometers process

1: Sample is vaporised

2: Sample is ionised to form positive ions

3: Ions are accelerated→ heavy ions move slower and are less deflected.

4: ions are detected as a mass to charge ratio written as m/z

What can a mass spectrum be used to calculate?

Relative atomic mass of an element

What do the ions produce during mass spectroscopy

A signal proportional to its abundance

What does relative molecular mass refer to

Substances with simple molecuyles