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Titel
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Kinetic molecular theory and atomic theory Topic1
Kinetic molecular theory and atomic theory
AIMS/OBJECTIVES
The overall aim for this module is to introduce 2i students to foundation knowledge of the Chemistry IB diploma course in Topic 1. The following subtopics are covered:
Particulate nature of matter Structure 1.1
The nuclear atom Structure 1.2
Electron configuration Structure 1.3
Periodic table basics Structure 3.1
This is both a theoretical and practical course with teacher demonstrations, student led experiments and group work to complement the individual tests, projects and exam.
ESSENTIAL IDEAS
Particulate nature of matter – Structure 1.1
Content Statement
Elements are the primary constituents of matter, which cannot be chemically broken down into simpler substances. The kinetic molecular theory is a model to explain physical properties of matter (solids, liquids and gases) and changes of state. The temperature, T, in Kelvin (K) is a measure of average kinetic energy Ek of particles.
The nuclear atom – Structure 1.2
Content Statement
Atoms contain a positively charged, dense nucleus composed of protons and neutrons (nucleons). Negatively charged electrons occupy the space outside the nucleus. Isotopes are atoms of the same element with different numbers of neutrons.
Electron configurations – Structure 1.3
Content Statement
Emission spectra are produced by atoms emitting photons when electrons in excited states return to lower energy levels. The line emission spectrum of hydrogen provides evidence for the existence of electrons in discrete energy levels, which converge at higher energies. The main energy level is given an integer number, n, and can hold a maximum of 2n2 electrons. A more detailed model of the atom describes the division of the main energy level into s, p, d and f sublevels of successively higher energies. Each orbital has a defined energy state for a given electron configuration and chemical environment, and can hold two electrons of opposite spin. Sub-levels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron.
Periodic table – Structure 3.1
Content Statement
The periodic table consists of period, groups and blocks. The periodic number shows the outer energy level that is occupied by electrons, elements in a group have a common number of valence electrons periodicity refers to trends in properties of elements across a period and down a group.
Trends in properties of elements down a group include the increasing metallic character of group 1 elements and decreasing non-metallic character of group 17 elements metallic and non-metallic properties show a continuum, this includes the trend from basic metal oxide through amphoteric to acidic non-metal oxides the oxidation state is a number assigned to an atom to show the number of electrons transferred in forming a bond ,it is a the charge that atom would have if the compound were composed of ions.
ACADEMICS SKILLS
Particulate nature of matter – Structure 1.1
Understandings and Outcomes
Be able to distinguish between the properties of elements, compounds and mixtures. Solvation, filtration, recrystallization, evaporation, distillation and paper chromatography should be covered. The differences between homogeneous and heterogeneous mixtures should be understood.
Distinguish the different states of matter. Use state symbols (s, l, g and aq) in chemical equations. Names of the changes of state should be covered: melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and deposition.
Interpret observable changes in physical properties and temperature during changes of state. Convert between values in the Celsius and Kelvin scales. The kelvin (K) is the SI unit of temperature and has the same incremental value as the Celsius degree (°C).
The nuclear atom – Structure 1.2
Understandings and Outcomes
Use the nuclear symbol XZ A to deduce the number of protons, neutrons and electrons in atoms and ions. Relative masses and charges of the subatomic particles should be known; actual values are given in the data booklet. The mass of the electron can be considered negligible. Perform calculations involving non-integer relative atomic masses and abundance of isotopes from given data. Differences in the physical properties of isotopes should be understood. Specific examples of isotopes need not be learned.
Electron configurations – Structure 1.3
Understandings and Outcomes
Qualitatively describe the relationship between colour, wavelength, frequency and energy across the electromagnetic spectrum. Distinguish between a continuous and a line spectrum. Details of the electromagnetic spectrum are given in the data booklet.
Describe the emission spectrum of the hydrogen atom, including the relationships between the lines and energy transitions to the first, second and third energy levels. The names of the different series in the hydrogen emission spectrum will not be assessed.
Deduce the maximum number of electrons that can occupy each energy level.
Recognize the shape and orientation of an s atomic orbital and the three p atomic orbitals.
Apply the Aufbau principle, Hund’s rule and the Pauli exclusion principle to deduce electron configurations for atoms and ions up to Z=36. Full electron configurations and condensed electron configurations using the noble gas core should be covered. Orbital diagrams, i.e. arrow-in-box diagrams, should be used to represent the filling and relative energy of orbitals. The electron configurations of Cr and Cu as exceptions should be covered.
Periodic table – Structure 3.1
Understandings and Outcomes
Identify the positions of metals, metalloids and non-metals in the periodic table. The four blocks associated with the sublevels s, p, d, f should be recognized. A copy of the periodic table is available in the data booklet.
Deduce the electron configuration of an atom up to Z=36 from the element’s position in the periodic table and vice versa. Groups are numbered from 1 to 18. The classifications “alkali metals”, “halogens”, “transition elements” and “noble gases” should be known.
Explain the periodicity of atomic radius, ionic radius, ionization energy, electron affinity and electronegativity.
Describe and explain the reactions of group 1 metals with water, and of group 17 elements with halide ions.
Deduce equations for the reactions with water of the oxides of group 1 and group 2 metals, carbon and sulfur. Include acid rain caused by gaseous non-metal oxides, and ocean acidification caused by increasing CO2 levels.
Deduce the oxidation states of an atom in an ion or a compound. Explain why the oxidation state of an element is zero. Oxidation states are shown with a + or – sign followed by the Arabic symbol for the number, e.g. +2, –1. Examples should include hydrogen in metal hydrides (–1) and oxygen in peroxides (–1). The terms “oxidation number” and “oxidation state” are often used interchangeably, and either term is
acceptable in assessment. Naming conventions for oxyanions use oxidation numbers shown with Roman numerals, but generic names persist and are acceptable. Examples include NO3– nitrate, NO2– nitrite, SO4 2– sulfate, SO3 2– sulfite.
SOURCES
- Chemistry for the IB Diploma Programme SL and HL Print and eBook
Pearson
- OUP Study Guide (Neuss): Pages 1 - 5
- OUP Study Guide (Neuss): Pages 9, 10 and 11
- OUP Study Guide (Neuss): Page 43
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ASSESSMENT/EVALUATION
(A brief description of how the students will be assessed and evaluated in this topic)
End of Topic exam, approximately 70 minutes long covering both multiple choice and short answer questions
NOS/TOK
1. How is the particulate nature of matter modelled?
This includes the importance of improvements in instrumentation to develop understanding of the structure of the atom such as the routes taken by alpha particles when fired at a thin sheet of gold which led to the Rutherford model of the atom replacing the 'plum pudding' model.
The work of Thomson and others showed that atoms can be broken down into smaller sub-atomic particles thus overthrowing the long held paradigm of atoms being indivisible.
Another example of the improvement in apparatus leading to developments in science is the use of electric and magnetic fields in Thomson's cathode ray tubes.
Quantum mechanics provides the basis for current models of the atom superseding the Bohr model.
Natural phenomena can be explained by theories. For example, line spectra can be explained by the Bohr model of the atom.
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