Chapter One The big picture – the Periodic Table
Handouts and Worksheets ‘The Chemical Investigator’ pages 5 – 11 Study On – worksheets 1 & 2
Matter • Every material thin that you can see, smell and touch, that occupies space and has mass, is a form of matter. • Matter is made up of very small particles and may exist in solid, liquid or gaseous states. • The behaviour of these particles is explained by the particle model, or kinetic theory of matter.
The Kinetic Theory of MatterKey Points • Matter is made up of tiny, invisible moving particles • Particles of different substances have different sizes • Lighter particles move faster than heavier ones at a particular temperature • As temperature rises, the particles move faster • In a solid, the particles are very close and vibrate in fixed positions • Ina liquid, the particles are a little further apart. They have more energy and they can move around each other • In a gas, the particles are far apart. They move rapidly and randomly in all the space that surrounds them.
Properties of Solids, Liquids and gases • Solidshave definite shapes and volumes • Crystalline solids (salt, diamonds) have particles arranged in regular, repetitive patterns • Particles are able to vibrate but not move • Amorphous solids do not have this regular structure (eg rubber, putty)
Properties of Solids, Liquids and gases • Liquidshave a definite volume, taking the shape of the container but their surfaces are always horizontal • Liquid particles move further apart than those in a solid and are in constant motion, free to move • Liquids can flow • Gasestake the same shape and volume as their container, free to move in any direction.
Matteris usually defined as anything that has mass and occupies space.
Disorder Some space Particles closer together Order Particles fixed in position Total disorder Lots of empty space Gas Liquid Solid
Solids, Liquids, and Gases • Gases have no defined shape or defined volume • Low density • Liquids flow and can be poured from one container to another • Indefinite shape and takes on the shape of the container. • Solids have a definite volume • Have a definite shape.
Review • Matter On the Move jeopardy revision • Complete revision questions page 4 (1 – 4). Check and review your answers
Changes in States of Matter • As temperature varies the particles change in energy and distance apart • Changing states of matter is about changing densities, pressures, temperatures, and other physical properties. The basic chemical structure does not change. • Summarise the terms: • Melting point, Freezing point, Evaporate, Boiling Point, Condensation Point, Volatile
Changes in States of Matter Draw the image with the appropriate terms
Review • Complete revision questions page 6 (5 – 7). Check and review your answers
Atomic theory Sub atomic particles
Atomic theory • The theory attempts to explain the microscopic structure of materials. • All Matter is made up of Atoms • Summarise the timeline (page 7) with the – date, scientist and major discovery.
fire Democritus earth air water Aristotle Early Greek Theories • 400 B.C. - Democritus thought matter could not be divided indefinitely. • This led to the idea of atoms in a void. • 350 B.C - Aristotle modified an earlier theory that matter was made of four “elements”: earth, fire, water, air. • Aristotle was wrong. However, his theory persisted for 2000 years.
John Dalton • 1800 -Dalton proposed a modern atomic model based on experimentation not on pure reason. • All matter is made of atoms. • Atoms of an element are identical. • Each element has different atoms. • Atoms of different elements combine in constant ratios to form compounds. • Atoms are rearranged in reactions. • His ideas account for the law of conservation of mass (atoms are neither created nor destroyed) and the law of constant composition (elements combine in fixed ratios).
Dalton’s Postulates • Every element is composed of tiny particles called atoms • All atoms of a given element are identical • Atoms of different elements have different properties • Atoms of an element are NOT changed into atoms ofanother element by chemical processes • Matter can neither be created nor destroyed • Compounds are formed when atoms of more than oneelement combine
Dalton’s Laws • The Law of Constant Composition: • “Any given compound always consists of the same atoms and the same ratio of atoms. For example, water always consists of oxygen and hydrogen atoms, and it is always 89 percent oxygen by mass and 11 percent hydrogen by mass” • 2. The Law of Conservation of Mass: • “The total mass of materials before and after a chemical • reaction must be the same. For example, if we combine • 89 grams of oxygen with 11 grams of hydrogen under • the appropriate conditions, 100 grams of water will be • produced—no more and no less.”
Dalton’s Laws 3. The Law of Multiple Proportions: “If two elements combine to form more than one compound,the masses of one of the elements that can combine with a given mass of the other element are related by factors of small wholenumbers” For example, water has an oxygen-to-hydrogen mass ratio of 7.9:1. Hydrogen peroxide, another compound consisting of oxygen and hydrogen, has an oxygen-to-hydrogen mass ratio of 15.8:1. The ratio of these two ratios gives a small whole number.
Adding Electrons to the Model Materials, when rubbed, can develop a charge difference. This electricity is called “cathode rays” when passed through an evacuated tube (demos). These rays have a small mass and are negative. Thompson noted that these negative subatomic particles were a fundamental part of all atoms. • Dalton’s “Billiard ball” model (1800-1900) Atoms are solid and indivisible. • Thompson “Plum pudding” model (1900) • Negative electrons in a positive framework. • The Rutherford model (around 1910) • Atoms are mostly empty space. • Negative electrons orbit a positive nucleus.
Zinc sulfide screen Thin gold foil Lead block Radioactive substance path of invisible -particles Ernest Rutherford • Rutherford shot alpha () particles at gold foil. Most particles passed through. So, atoms are mostly empty. Some positive -particles deflected or bounced back! Thus, a “nucleus” is positive & holds most of an atom’s mass.
Bohr’s model • Electrons orbit the nucleus in “shells” • Electrons can be bumped up to a higher shell if hit by an electron or a photon of light. There are 2 types of spectra: continuous spectra & line spectra. It’s when electrons fall back down that they release a photon. These jumps down from “shell” to “shell” account for the line spectra seen in gas discharge tubes (through spectroscopes).
The Structure of Atoms • Summarise and/or define: • Nuclear model of the atom, Protons, Neutrons, Electrons, Sub-atomic particles, Ions, Elements, Atom, Atomic number, Mass number, Isotopic symbol, Isotopes, Atomic emission spectrum.
16 E.g. Oxygen: O 8 Atomic numbers, Mass numbers • There are 3 types of subatomic particles. We already know about electrons (e–) & protons (p+). Neutrons (n0) were also shown to exist (1930s). • They have: no charge, a mass similar to protons • Elements are often symbolized with their mass number and atomic number • These values are given on the periodic table. • For now, round the mass # to a whole number. • These numbers tell you a lot about atoms. • # of protons = # of electrons = atomic number • # of neutrons = mass number – atomic number • Calculate # of e–, n0, p+ for Ca, Ar, and Br.
Atomic Mass p+ n0 e– Ca 20 40 20 20 20 Ar 18 40 18 22 18 Br 35 80 35 45 35
Review • Complete the revision questions page 9 (8 – 11). Check and review your answers • What is the symbol for the Atomic number? • Z • What is the symbol for the Mass number? • A
Isotopes and Radioisotopes • Atoms of the same element that have different numbers of neutrons are called isotopes. • Due to isotopes, mass #s are not round #s. • Li (6.9) is made up of both 6Li and 7Li.relative atomic mass • Often, at least one isotope is unstable. • It breaks down, releasing radioactivity. • These types of isotopes are called radioisotopes Q- Sometimes an isotope is written without its atomic number - e.g. 35S (or S-35). Q- Draw B-R diagrams for the two Li isotopes. A- The atomic # of an element doesn’t change Although the number of neutrons can vary, atoms have definite numbers of protons.
3 p+ 3 n0 3 p+ 4 n0 2e– 1e– 2e– 1e– 6Li 7Li Isotopes Isotopes of Lithium illustration For more lessons, visit www.chalkbored.com
Isotopes • All atoms of a particular element have the same number of protons. • Atoms with the same number of protons but a different number of neutrons are called isotopes • Isotopes have similar chemical properties because their electron structure is the same. They have different physical properties due to their different masses. • List the three naturally occurring isotopes of oxygen.
Oxygen • Isotopes of Oxygen • There are three stable isotopes of oxygen that lead to oxygen (O) having a standard atomic mass of 15.9994(3) amu • Naturally occurring oxygen is composed of three stable isotopes, 16O, 17O, and 18O, with 16O being the most abundant (99.762% natural abundance). Known oxygen isotopes range in mass number from 12 to 24
Review • Work through the sample problem on page 10 • Complete the revision questions pages 10, 11 (12 – 17). Check and review your answers.
Atomic Emission Spectrum • Every element emits light if it is heated by passing an electric discharge through its gas or vapour • This happens because the atoms of the element absorb energy, then lose it and emit it as light. • Atomic emission spectrum consist of separate lines of coloured light, each line of the spectrum corresponding to one particular frequency of light being given off by the atom: therefore each line corresponds to one exact amount of energy being emitted.
Electrons orbit the nucleus in “shells” Bohr’s model • Electrons can be bumped up to a higher shell if hit by an electron or a photon of light. There are 2 types of spectra: continuous spectra & line spectra. It’s when electrons fall back down that they release a photon. These jumps down from “shell” to “shell” account for the line spectra seen in gas discharge tubes (through spectroscopes).
3 p+ 4 n0 2e– 1e– Bohr - Rutherford diagrams • Putting all this together, we get B-R diagrams • To draw them you must know the # of protons, neutrons, and electrons (2,8,8,2 filling order) • Draw protons (p+), (n0) in circle (i.e. “nucleus”) • Draw electrons around in shells He Li Li shorthand 3 p+ 4 n0 2 p+ 2 n0 Draw Be, B, Al and shorthand diagrams for O, Na
Be B 4 p+ 5 n° 5 p+ 6 n° O Na 8 p+ 8 n° 11 p+ 12 n° 2e– 6e– 2e– 8e– 1e– Al 13 p+ 14 n°
Bohr’s energy levels • How does Bohr’s model explain the Atomic Emission Spectrum. • Define the terms: ground state, energy levels, excited state, photon • Why does Bohr’s model not explain atoms more complex than Hydrogen? • What is the Quantum mechanics model?
Electron Shells • The regions of space surrounding the nucleus. • The electron shells are labelled K, L, M, N and numbered 1, 2, 3, 4 • A definite energy level is associated with each shell (K – closest the nucleus – lowest energy). Therefore an electron has to gain energy to move away from the nucleus.
Electron Shells • If an electron gains enough energy to completely leave the atom, the particle that is left is not longer neutral and called a positive ion. • Explain how K can become K+. What is the difference in the protons and electrons when K becomes a positive ion?
Electron Configuration • Electron configuration – arrangement of electrons in shells • The maximum number of electrons that each shell can hold is 2n2 where n is the number or energy level
Electron Configuration • Electron shells are filled in order from the nucleus (lowest energy level first – K) • For the first 20 elements the outer shell never has more than 8 electrons • The outer shell electrons mainly determine the chemical properties of an element.
Electron Configuration • Each electron has its own distinct energy, this energy corresponds to the energy level it occupies • Electrons can gain or lose energy, but that amount of energy gained or lost is a fixed amount of energy. • This fixed amount of energy gained allows an electron to move to a higher energy level.
Electron Configuration • Ground state – electrons occupy the lowest available oribitals. • Excited state – unstable condition, electrons temporarily move to a higher energy level. • When electrons are subject to stimuli such as heat, light, or electricity, electrons may absorb energy and temporarily move to a higher energy level.
Electron Configuration • Chemical properties are based on the number of electrons in the outer energy level. • Valence electrons are these outer electrons. • Quantum theory – explains chemical behaviourof atoms. • Quantum numbers – electrons are described as a set of four numbers
Electron Configuration • First number describes the major energy level of the electron and is called the principle energy level. • Principle energy levels have sublevels. There are as many sublevels as the number of that energy level. • s is the first sublevel, p is the second, d is the third and f is the fourth. • ie) 3s means third energy level and first sublevel
Electron Configuration • Electron configuration – distribution of electrons in an atom. • Electron configuration for oxygen would be 1s22s22p4
Review • Atomic structure on line multiple choice • Periodic Table quiz • atomic structure quiz • Complete the revision questions pages 14, 15 (18 – 22). Check and review your answers.