Isotopes and Compounds Flashcards
What are isotopes (characteristics and properties)?
2 atoms of the same element with the same no. of protons but with different masses resulting from their no. of neutrons.
Characteristics: same atomic no., different mass. Natural or synthesised, similar chemical properties because of the same no of electrons. Different physical properties.
Properties: Different masses, densities and variations in nuclear stability.
What are radioactive isotopes and half-lives?
Half-life: The time taken for half the atoms in a sample to decay to a new element/isotope.
Radioactive: Unstable nuclei will undergo radioactive decay. High energy particles/radiation is emitted which can be used for radioactive dating.
What is tagging chemical reactions?
Chemical reactions inside the human body can be examined by placing isotopic traces into molecules. The isotopic tracer can then be traced through the human body so that chemical reactions can be investigated.
Isotopes are used in medicine to diagnose diseases and to treat specific illnesses like cancer.
What is RAM and its formula?
Relative atomic mass is the average mass of atoms of a chemical equation compared to a standard atom. Isotopes of the same element have different atomic masses and different abundances.
RAM = ((Abundance % x atomic mass)+(abundance % x atomic mass))/100
What are pure substances?
Some elements were discovered in their elemental form (copper, silver, gold) due to their low reactivity.
In early 1800’s, electrolysis technology enabled isolation of potassium from the compound caustic potash, and calcium from quicklime.
Some elements have been synthetically discovered through particle acceleration and nuclear fusion.
Pure substances physical and chemical properties?
Physical: melting and boiling points, electrical and thermal conductivity, density and solubility.
Chemical: Reactivity, stability, toxicity and flammability.
Chemical processes?
Processes can break down compounds into simpler substances.
Observations that indicate this process is…
Solid forms or disappears, gas is produced (evolved), colour and temperature change.
What is homogeneous, heterogeneous and a plain mixture?
Mixtures are made of two or more pure substances (elements and/or compounds).
Homogenous mixtures have uniform composition throughout. Means super well mixed its hard to tell the difference between mixtures/elements.
Heterogenous mixtures have a non-uniform composition. They are not well mixed and it’s easy to see the different bits in them. Sometimes you need to use an optical microscope to observe the non-uniformity of a heterogeneous mixture.
One of the primary ways of modifying the properties of pure metallic elements is by alloying them with other elements in homogenous mixtures.
What are carbon allotropes?
Carbon can exist in many different elemental forms called allotropes, due to different bonding structures.
Some allotropes have an amorphous shape (non-crystalline).
What are substitution and Interstitial alloys?
Substitution alloys – An alloy where the dopant has been substituted into the crystalline structure with the main atoms.
Interstitial alloys – An alloy where the dopant occupies the space between the main atoms.
What are distillation and fractional distillation?
Distillation can be used to separate multiple solvents from solution based on their boiling points (alcohol production).
Fractional distillation is used to separate the hydrocarbons in crude oil into useful substances like natural gas, petrol, and diesel.
What is separating mixtures?
A mixture of two solids can be separated by dissolving one substance (salt in water), and filtering out the insoluble solid (sand).
A mixture of two solutes that are soluble in one solvent, such as salt and copper sulfate in water, can be separated by recrystallising in a different solvent, such as ethanol.
Definitions of macroscopic observations, optical microscopes and electron microscopes?
Macroscopic observations (naked eye) can discern objects at the millimeter scale (106 nm).
Optical microscopes can distinguish individual bacteria on the micrometer scale (1000 nm).
Electron microscopes have a resolution of <0.1 nm and so are used in nanotechnology (1-100 nm) investigations of nanomaterials, such as viruses, antibodies, and molecular structures.
Definitions of fullerenes, graphene and nano-particles?
Fullerenes – used in medical applications to encapsulate various ions/molecules e.g. gadolinium(III) ions to reduce toxicity in MRI’s.
Graphene – used to produce semiconductors, electronics, and carbon nanotubes which have future applications in medicine and next generation energy storage.
Nanoparticles – Already being used the manufacture of scratchproof eyeglasses, anti-graffiti coatings for walls, transparent sunscreens, stain-repellent fabrics, self-cleaning windows, ceramic coatings for solar cells and drug delivery systems.
