Chemistry OCR structure of atom and isotopes

1.1

Who discovered the electron and when?

J.J. Thomson in 1897

Who discovered the proton and when?

Ernest Rutherford in 1917

Who discovered the neutron and when?

James Chadwick in 1932

Symbol for proton

p+

Relative mass of a proton

1

Relative charge of a proton

+1

Position of a proton in an atom

Nucleus

Symbol for neutron

n0

Relative mass of a neutron

1

Relative charge of a neutron

0

Position of a neutron in an atom

Nucleus

Symbol of electron

e-

Relative mass of an electron

1/1840

Relative charge of an electron

-1

Position of an electron in an atom

Energy shells surrounding the nucleus

Atomic number definition

Number of protons in an atom

Mass number definition

Number of protons and neutrons in an atom (mass of protons and neutrons in an atom)

Isotope definition

Atoms of the same element with the same number of protons but different numbers of neutrons

Relative atomic mass definition

The average mean mass of an atom of an element compared to 1/12th the mass of carbon-12 (which has a mass of 12)

Relative isotopic mass definition

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

What is a mass spectrometer?

A device that measures the masses of atoms and molecules

How does a mass spectrometer work?

It produces positive ions that are deflected by a magnetic field according to their mass to charge ratio (m/z)

What does a mass spectrometer show?

It calculates the relative abundance of each positive ion and displays it as a percentage

What positive ions can be used in a mass spectrometer?

Positively charged atoms, positively charged molecules or positively charged fragments of molecules

How to determine relative isotopic and atomic masses

Using a mass spectrum of an element, you can determine the exact values of the relative masses of isotopes and their percentage abundance

How to find the approximate isotope abundance using a mass spectrum

Use the mass spectrum to find the ratio of approximate relative peak heights of each isotope

Molecular ion peak definition

The peak on a mass spectrum with the highest m/z (mass to charge) ratio - called the M peak