Lecture 2 - Structure of Matter Flashcards
Describe the Bohr model of the atom in terms of its particle makeup.
The Bohr model of the atom describes electrons as orbiting the nucleus at fixed energy levels. This can illustrated through the hydrogen atom. One proton in the nucleus and one electron orbiting around it.
Use the nuclide notation to describe elements and their isotopes.
State the nuclide notation for the following 6 elements: Hydrogen, Helium, Carbon (12-14), Oxygen, Magnesium, Uranium and Chlorine.
A(X)
Z(X)
1,1 H; 4,2 He; 14,6 C; 13,6 C; 12,6 C; 16,8 O; 24,12 Mg; 235,92 U; 35,17 Cl; 37,17 Cl
Identify 5 different sections in the periodic table and explain the basic physical and chemical properties of elements in these sections.
(1) The group 1 elements are known as the alkali metals and are all highly reactive as room
temperature and atmospheric pressure, especially moving further down the group.
(2) The alkali earth
metals form the elements in group 2.
(3) The elements in the middle of the periodic table in groups 3-12 are known as the transition
metals. They are good conductors of heat and electricity, malleable, less reactive than the
alkali metals, and have both high densities and melting points.
(4) The metalloids are the elements found along the step like line between metals and non-metals
of the periodic table. Metalloids have properties of both metals and non-metals
(5) At the other end of the periodic table, group18 are the noble or inert gasses. In terms of
electron configuration, the outer shells noble gases are all full which them highly unreactive.
Understand the basic operation of a mass spectrometer.
For identifying substances/isotopes – measure the charge-to-mass ratio of the
components that make up the substance: Full details in lecture slides, which includes
explanations of the 3 key stages:
[i] – Ionisation: Atoms or molecules are converted into ions by removing an electron in the process of ionizing them. This is done to produce negatively charged fragments that can be separated and analyzed according to their masses.
[ii] – Mass analyzer: Ions are separated based on their mass-to-charge ratio (m/z) using a mass analyzer. In this way, ions of different masses are separated from each other and directed towards the detector.
[iii] – Detection: The separated ions are detected by a detector that measures the intensity of the ion beam as a function of m/z. This allows for the creation of a mass spectrum, which is a plot of ion abundance versus m/z.
Define radioactivity
Radioactive decay is defined as the
spontaneous and disintegration of the nuclei of some nuclides (known as radionuclides) with
the emission of alpha [α], beta [β-] or positron [β+] particles, sometimes accompanied by a
gamma [γ] ray
Describe the mechanisms which lead to unstable radio-nuclides
Unstable radio-nuclides occur when the nucleus has an imbalance between the number of protons and neutrons, leading to an unstable configuration.
This imbalance triggers the nucleus to undergo radioactive decay, releasing energy in the form of particles or electromagnetic radiation to achieve a more stable configuration.
Describe the characteristics of alpha, beta, positron and gamma radiation and the meaning of radioactive half-life.
Alpha radiation: Helium nuclei (He²⁺ particles) emitted from an unstable nucleus, with low penetrating power but high ionizing ability.
Beta radiation: Electrons or positrons (positively charged electrons) emitted from an unstable nucleus, with moderate penetrating power and intermediate ionizing ability.
Gamma radiation: High-energy electromagnetic radiation emitted from an unstable nucleus, with high penetrating power but low ionizing ability.
Radioactive half-life: The time required for half of the radioactive atoms in a sample to decay, a constant value for a given isotope.
Express radioactive decay processes using balanced decay equations.
239, 94 Pu -> 235, 92 U + 4,2 He + energy
14, 6 -> 14,7 N + 0,-1e + energy
What is a radiological attack? How is this applicable in an urban context?
A radiological attack involves the intentional spread of radioactive material to harm people or disrupt critical infrastructure. In an urban context, such an attack could have devastating consequences due to the high population density and interconnectedness of systems.
May lead to health risk to those exposed.
What is the unit of measurement for radioactivity?
Becquerel describes the rate at which radioactive material emits radiation (termed Activity).
1 curie = 3.7x10*10 Bq
Protons and neutrons are collectively known as
[a] Nucleons
[b] Cations
[c] Alpha (α) particles
[d] Anions
[e] Electrons
(a)
In an atom, the force which provides the attraction between negative electrons and the
positive nucleus is called the
[a] Electrostatic force
[b] Gravitational force
[c] Strong force
[d] Repulsive force
[e] Weak force
(a)
In the periodic table, the elements in group 18 are commonly known as:
[a] The noble or inert gases
[b] The alkaline earth metals
[c] The reactive gasses
[d] The metalloids
(a)
The element gold (symbol [Au]) has atomic number Z = 79 and mass number A = 197. How
many neutrons are contained in the nucleus?
N = 118
The element gold (symbol [Au]) has atomic number Z = 79 and mass number A = 197. How
many neutrons are contained in the nucleus?
1.661 x10-27 x 4 = 6.644 x10-27 kg
