Structure 1.2 The Nuclear atom

Structure 1.2.1 Structure 1.2.2 Structure 1.2.3

List the key features of the nucleus of an atom

1. It’s very small in comparison to the atom itself.

2. It’s a highly dense structure containing virtually all the mass of the atom.

3. It has a positive charge.

What was the ‘plum-pudding model’ falsified by?

It was falsified by Ernest Rutherford’s gold foil experiment.

• Plum-pudding model suggested that the atom was an amorphous positively charged ball with electrons present throughout.

• The gold foil model showed that the radioactive alpha particles were slightly deflected, completely deflected and undeflected.

Describe the Rutherford model

Negatively charged electrons orbit the positively charges atomic nucleus where the electrons are held around the nucleus by electrostatic attraction

What is the relative mass and charge of a proton?

mass: 1
charge: +1

What is the relative mass and charge of a neutron?

mass: 1
charge: 0

What is the relative mass and charge of an electron?

mass: negligible
charge: -1

what is the electric charge carried by a single electron called? what is it’s value?

Elementary charge (e)
1.602 × 10^-19 C

What are Isotopes?

Different atoms of the same element with different number of neutrons but the same number of protons
[they have similar chemical properties but different physical properties]

List the 3 Isotopes of Hydrogen

1. Protium (hydrogen-1)

2. Deuterium (hydrogen-2)

3. Tritium (hydrogen-3)

Define Relative Atomic Mass

the average mass of the naturally occurring isotopes of an element relative to 1/12 of an atom or carbon 12

Define Isotope labelling

a technique used to track the passage of an isotope through chemical reaction, metabolic pathway, or a biological cell.

Formula for calculating the average of the Natural Abundance (Ar)

What is a mass spectrometer used for?

Detect the relative abundance of isotopes in a sample

Describe the process of mass spectrometry

1. The sample is injected and vaporized

2. sample bombarded with high-energy electrons

3. atoms lose some of their electrons to form cations

4. The ions are accelerated by an electric field

5. The ions are then deflected by a magnetic field

6. The degree of deflection depends on the mass to charge ratio (deflected most: lowest mass; highest charge)

7. Ions hit the detector; the m/z values are determined and passed to a computer

8. Mass spectrum generated [m/z ratio against relative abundance]