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chem 1.1.1
atoms and elements,trends, critical elements
| Term | Definition |
|---|---|
| Atoms | the basic building blocks of matter, Protons and neutrons sit in the dense nucleus. Electrons orbit the nucleus in specific energy levels |
| Elements | substances made up of only one type of atom |
| Compounds | substances that contain two or more elements |
| Molecules | group of atoms that are covalently bonded. Group can be made of the same atom or 2+ different atoms |
| atomic number | number of protons in the nucleus of an atom of that element. |
| mass number | total number of protons AND neutrons in the nucleus of an atom of that element |
| Isotopes | same atomic number but different number of neutrons |
| isotopes have diff physical prop such as | mass, density, boiling and melting point |
| electromagnetic radiation | light, photon |
| atomic emission spectrum | black background and a number of coloured lines. appears when atoms give off radiation in the visible region of the spectrum |
| Ground state | the lowest energy, most stable arrangement of an e |
| Excited state | a higher energy arrangement |
| brief summary of emission spectra | the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule transitioning from a high energy state to a lower energy state |
| flame test summary | Some metallic elements can be identified through their flame colours when heated |
| limitations to flame test | Not sensitive technique, Limited scope of metal ions, Contamination results in inaccuracy, Difficulty distinguishing the flame colour |
| The quantum-Mechanical model postulates that | electrons do not move in a definite path but in a region of space around the nucleus called an orbital |
| Metals properties | solid at room temperature, shiny, conduct electricity, malleable |
| Non-metals properties | gas at room temperature, dull, poor conductors and brittle |
| Metalloids properties | are not classed as either and have similar properties to both |
| Core charge | the attractive force between the nucleus and the valence shell electrons |
| core charge formula | cc = p - (inner shell e) |
| core charge of noble gases | 0 |
| Shielding | occurs when more inner shells are added to an atom. The greater the e shielding, the weaker the attraction between the nucleus and outer shell e |
| Atomic radius | the size of the atom, and is the typical distance from the nucleus to the edge of the surrounding electron cloud |
| trend of atomic rad across p and why | decreases, A higher core charge will result in greater attraction by the nucleus to the valence electrons, thus lowering atomic radius as the pull is greater |
| trend of atomic rad down group and why | increases, The increased shielding lowers the attractive forces felt by the nucleus and the valence electrons of an atom, thus increasing atomic radius as the shell number increases |
| Electronegativity | the ability of an element to attract free-bonding electrons to itself |
| trend in electronegativity across p and why | increases, The increase in core charge means an increase in attraction between the nucleus and bonding electrons OF OTHER ELEMENTS, which results in greater electronegativity |
| trend in electronegativity down a group and why | decreases, Greater shielding means that the attraction between the nucleus and the bonding electrons OF OTHER ELEMENTS has decreased, which results in less electronegativity. |
| Ionisation energy | the amount of energy required to remove an electron from an atom or ion in the gaseous state |
| trend in ionsation energy across a period and why | increases, increase in core charge means an increase in attraction between the nucleus and valence electrons, which results in a higher 1st IE. because it takes more energy to remove the electron |
| trend in ionsation energy down a group and why | decreases, increase in shielding means that the attraction between the nucleus and the valence electrons has decreased, so less energy is needed to remove the 1st electron |
| reactivity | of the ability of an atom to undergo a chemical reaction |
| Octet rule | an atom is the most stable when its valence shell has a full 8 e |
| reactivity trend across a period and why | The easier it is for an atom to lose an electron, the more reactive the metal, and the easier it is for an atom to gain an electron, the more reaction the non-metal |
| reactivity trend down a group and why | increased shielding decreases the attraction between the nucleus and valence electrons, which makes it easier for the electrons to form other bonds, thus increasing the reactivity down groups |
| metallic character | the ability of an atom to donate electrons |
| trend of metallic character across a period | decreases, The increase in core charge means there is a greater attraction between the nucleus and the valence electrons, so the ability to donate electrons decreases because the electrons are more tightly held together |
| trend of metallic character down a group | increases The increased shielding lessens the attraction between the nucleus and the valence electrons, which makes it easier for the atom to donate electrons as the atom is more loosely held together. |
| critical elements | those that are considered vital for the world’s economy but are in short supply. difficult and expensive to recover because they are left in an |
| how to be more sustainable (critical elements) | our new developments must meet the current demands of these elements without impacting the needs and ability of future generations |
| grene chemitry | the manufacturing of chemical products or processes that decrease the use of harmful substances that can impact human health and the environment. |
| linear economy | after use we waste it |
| circular economy | after use we try to recycle it and take whatever available resources to reuse |
| Helium | second most abundant element in the universe but critical on Earth |
| properties of helium | Leaks from the Earth’s atmosphere into space and becomes unrecoverable. Inert so doesn’t form compounds that can trap it on Earth |
| production of helium | By-product of natural gas extraction, Formed underground as the result of the natural decomposition of radioactive elements such as uranium-238 |
| helium's liquid form | reaches colder temperatures than any other element. used for MRI machines, nuclear reactors, rocket engines, balloons |
| purpose of Phosphorus | essential to all life functions |
| uses of phosphorus | Backbone of DNA, involved in energy transport, present in cell membranes and bones . Widely used as a fertiliser |
| how does phosphorous become a part of an ecosystem and why is it dangerous? | through decaying organic matter, the run-off into waterways causes eutrophication |
| eutrophication | when excess nitrogen or phosphorus in water results in excessive algal growth affecting the living organisms. |
| Solutions to preserve phosphorus | include recycling waste to extract phosphorus and minimising the use of fertilisers |
| Rare Earth Elements (REE) | not rare, but once used cannot be easily recycled. Difficult to mine and don’t exist in their pure form |
| How is indium sourced? | produced mainly from residues generated during zinc ore processing |
| Properties of Indium | conducts electricity well, is transparent and adheres to glass. |
| Mining for REEs | is destructive to the environment. Innovative technologies need to be developed to extract these elements economically and sustainably. |
Created by:
pg0612345
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