Atomic structure and the periodic table (2) Flashcards
What is a compound ?
Substances that contain two or more elements that are chemically combined in a fixed position (chemically bonded together)
What is a mixture ?
Give an example
A substance made up of two or more elements that are not chemically bonded together.
e.g - Sea water is a mixture of difference salts of gases
How do the chemical properties of a substance change when it’s in a mixture ?
The chemical properties of a substance do not change when it’s in a mixture
Describe how to separate an insoluble solid from a liquid using FILTRATION
1- Put a cone of filter paper into a filter funnel
2- Hold the funnel over a beaker and pour the mixture into it
3- The liquid will pass through the beker and the insoluble solid will be left i the filter paper
Describe how to separate a soluble solid from a solution using CRYSTALLISATION
1- Gently heat the solution to evaporate some of the solvent
2- Remove the heat and leave the solution to cool so crystals form
Tip - The crystal can be separated from any remaining solution by filtration
Describe how to separate a liquid from a solution using SIMPLE DISTILLATION
1- Add the solution into a distillation flask and connect a condenser to cool and condense the vapor back into liquid.
2- Heat the solution until the liquid with the lowest boiling point starts to vaporise
3- the vapor will rise into the condenser, cooling down and turning back into liquid
4- Collect the liquid in a receiving flask
Describe how to separate a mixture of liquids using FRACTIONAL DISTILLATION
1- Heat the mixture in a flask attached to a fractional column
2- when the boiling point of one of the liquids is reached, it’ll evaporate and exit at the top of the fractional column - it can be condensed and collected
3- Different liquids will evaporate as the temperature rises, so they can be condensed and collected separately
what is an atom’s mass number?
The total number of protons and neutrons in an atom
What is an atom’s atomic number?
The number of protons in an atom
What is the relative atomic mass (Ar) of an element ?
The average mass of an atom of an element that takes into account the abundance of the isotopes of the element.
How is the relative atomic mass (Ar) of an element calculated ?
1- For each isotope, work out :
% abundance x mass number
2 - Add them all up
3- Divide the total by 100
When is an atom most stable ?
An atom is most stable when the outer shell of electrons is full
What does the formula of a compound show ?
The formula of a compound shows the atom of the element that makes up the compound and the proportion they are in
How are compounds formed
A pure substance made from more than one type of elements chemically bonded together
How can compounds be separated into elements ?
Compounds can only be separated into elements by chemical reactions
Give 5 methods of separating mixture
- Filtration
- Crystallisation
- Fractional distillation
- Simple distillation
- Chromatography
What is an atom ?
The smallest part of an element that can exist
What is an element ?
A substance that consists of only one type of atom (with the same number of protons) and it cannot be broken.
How many elements are there ?
118 elements
What is the mass of :
Proton
Neutron
Electron
Protons - 1
Neutrons - 1
Electrons - 0 / very small
Where is almost all the mass of an atom found ?
In the nucleus
How is the number of electrons in an atom related to its atomic number ?
The number of electrons is the same as atomic number
What is the relative electrical charge of :
Proton
Neutron
Electron
Proton = +1
Neutrons = 0
Electrons = -1
Why does an atom have no overall electrical charge ?
Because it has the same number of protons and electrons
