Atomic Structure And The Periodic Table Flashcards
What are All substances made out of
Atoms
What is an atom
The smallest part of an element
What are atoms of each element represented by
Chemical symbols
What are compounds formed from
Elements by chemical reactions
What do chemical reactions always involve
Formation of one or more new substance and a detectable energy change
What do compounds contain
Two or more elements chemically combined in fixed proportions
How can chemicals be separated into elements
By chemical reactions
What does a mixture consist of
Two or more element not chemically combined together
How can mixtures be separated
Filtration simple distillation fractional distillation crystallisation and chromatography
How to do chromatography
It’s used to separate substances in a mixture like dyes and ink
You draw a line near the bottom on chromatography paper in pencil as is insoluble and won’t dissolve
Add spot of i k on line and place the sheet in water below the line
Place lid on top of container to stop solvent from evaporating
Wait for solvent to travel up then leave to dry
The final pattern is called a chromatogram
What is filtration
Can be used if product is insoluble
You use filter paper and pour mixture through and insoluble substance will stay stay behind
What is evaporation
It’s to separate soluble from solution that doesn’t decompose when heated
Pour solution into evaporation
Slowly heat solution and the solution will evaporate and solvent will start to crystallise
What is crystallisation
It’s used to separates solvents that’s decomposes when heated
Pour solution in evaporation dish
Heat gently
Crystals form
Filer out crystals
What is simple distillation
Used to separate liquids with different boiling points
Solution is heated and parts of solution with lowest boiling point Evaporates first
The vapour then cools and condenses and is collected
Rest of solution is left in flask
Why might a scientific model be changed or replaced
New experimental evidence
What did scientists think atoms were before the discovery of electrons
Tiny spheres that couldn’t be divided
What did the discovery of electors lead to
Plum pudding model
What was the plum pudding model
The idea that atoms were balls of positive charge with negative electrons embedded in it
What was the alpha particle scattering experiment
When particles were shot through a sheet of gold some went straight through some also deflected and some deflected backwards
What did the scattering experiment lead to
The nuclear model
Suggesting that electrons orbit around the nucleus at specific distances which his calculations helped explain other scientists observations
What did further experiments lead too
The discovery that the nucleus can be divided into smaller particle which alphabets the same charge as a hydrogen nucleus these were called protons
20 years later scientists accepted that atoms have a nuclei as James Chadwick carried out an experiment that provided evidence for neutral particles which were called neutrons
What does the number of electrons equal to
The number of protons in the nucleus
