C1 - Atomic Structure and The Periodic Table Flashcards
What are all substances made out of?
Atoms
What is the estimated radius of an atom?
0.1 nanometres
Where is the nucleus in the atom?
In the middle
What is the nucleus made up of?
Protons and neurons
What is the estimated radius of a nucleus?
1x10^-14m
What is the charge of a nucleus?
Positive
How much of the atoms mass is in the nucleus?
Nearly the whole mass
Where are the electrons in the atom?
Around the nucleus in electron shells
What charge are electrons?
Negative
How much mass do electrons have?
Virtually none
What determines the size of an atom with electrons?
Their orbit
What charges are atoms?
Neutral
Why are atoms neutral?
They have the same amount of protons as electrons. Therefore they cancel out the charge
What is an ion?
An atom or group of atoms that has lost or gained electrons. For example, an ion with a 2- charge would have 2 more electrons that protons
What does the nuclear symbol of an atom tell you?
The atomic proton number and mass number
Atomic number
Tells you how many protons there are
Mass number
Tells you the total number of protons and neutrons in the atom
How can you get the number of neurons from the nuclear symbol?
Atomic number - mass number
What is an element
A substance made up of atoms that all have the same number of protons in their nucleus
Isotopes
Different forms of the same element, which have the same number of protons but a different number of neutrons. So they have the same atomic number but different mass numbers
What is used if there are too many isotopes for a single element?
They use a relative atomic mass which is an average mass taking into account the different masses and abundances of all the isotopes that make up that element
Relative atomic mass (Ar) formula
sum of (isotope abundance x isotope mass number) / sum of abundances of all isotopes
Compounds
Substances formed from 2 or more elements, each are in fixed proportions throughout the compounds and held together by chemical bonds
How are bonds formed?
Either giving an atom away, taking or sharing an electron. Only electrons are involved (nuclei aren’t changed). The reaction is quite hard to revert
Ionic bonding
Metal atoms lose electrons to form positive ions and non-metal atoms gain electrons to form negative ions. The opposite charges of the ions mean that they are strongly attracted to each other and cancel each other out (neutral)
Molecule
Compounds formed from non-metals
Covalent bonding
Each atom shares an electron with another atom
Properties of compounds vs their original elements
Very different chemically and physically
Format of symbol equation
x y z
x + y -> z
What do chemical changes show
The atoms on both sides but they have to be equal because of the law of conservation of mass
Mixtures
Lots of separate things but aren’t chemically bonded together with a chemical bond. They can consist of elements or compounds
Is air a mixture?
Yes
Do the properties of mixtures change?
No because they aren’t chemically changed
Examples of mixture separation techniques
Chromatography, filtration, evaporation, crystallisation, (fractional) distillation
Chromatography
Paper chromatography is used to separate mixtures of soluble substances. These are often coloured substances such as food colourings, inks, dyes or plant pigments.
Chromatogram
The end result of the pattern created by chromatography