Topic 1: Atomic Structure and the Periodic Table Flashcards
What is an atom?
The smallest part of an element that can exist
Proton:
i) mass
ii) charge
i) 1
ii) +1
Neutron:
i) mass
ii) charge
i) 1
ii) 0
Electron:
i) mass
ii) charge
i) very small
ii) -1
What is the number of protons equal to?
The number of electrons
What does atomic number show?
Number of protons
What does the mass number show?
Number of protons + neutrons
What is an ion?
An atom without charge
What is an isotope?
Different forms of the same element with the same number of protons but a different number of neutrons
How do you calculate relative atomic mass?
(isotope abundance x isotope mass number) / sum of abundance of all isotopes
What is a molecule?
Two or more atoms, held together by a chemical bond
What is a compound?
Two or more different elements, held together by chemical bonds
What is a mixture?
Two or more substances, not chemically bonded
In chromatography, why should the line be drawn with pencil?
Pencil marks are insoluble so won’t dissolve in the solvent
In chromatography, why should you make sure the ink isn’t touching the solvent?
To stop the ink dissolving into it
What is chromatography used to do?
Separate substances in a mixture
What is filtration used to do?
Separate insoluble solids from liquids
What is evaporation used to do?
Separate soluble solids from solutions
What is crystallisation used to do?
Separate soluble solids from solutions
When does crystallisation have to be used instead of evaporation?
If the salt decomposes when it’s heated
Explain how you would separate rock salt using filtration and crystallisation [4]
- Grind the rock salt to make sure the salt crystals are small, so will dissolve easily
- Put the mixture in water and stir - salt will dissolve, but the sand won’t
- Filter the mixture - the sand will collect on the paper but the salt will pass through in the solution
- Evaporate the water from the salt so that it forms dry crystals
What is rock salt a mixture of?
Sand and salt
What is simple distillation used to do?
Separate out solutions
What is the problem with simple distillation?
It can only be used to separate liquids with very different boiling points
What is fractional distillation used to do?
Separate a mixture of liquids
What did the atomic theory (Democtritus) state? [2]
- Everything is made from tiny particles, which can’t be broken down any further
- They are separated by empty space
What did John Dalton conclude? [2]
- Atoms were solid spheres
- Different types of spheres make up the different elements
What did the plum pudding model (J.J. Thomson) state?
The atom is a ball of positive charge with electrons stuck in it