Chemistry Knowledge Organiser C1 - Atomic structure Flashcards
(22 cards)
Elements
• An element contains only one type of atom. All elements are given a symbol
and are found on the periodic table. You need to learn the symbols for the
first 20.
• The Periodic Table is arranged into groups (columns) and periods (rows), as
shown below.
Elements in the same group have:
• The same number of electrons in their outer shell
• Similar properties
Elements in the same period have:
• The same number of electron shells
Element
A substance that contains only one type of atom
The Conservation of Mass
• In a chemical reaction, chemical bonds are broken the atoms
are rearranged and the chemical bonds are made again.
• In a chemical reaction, mass is never lost, you must start
and finish with the same mass.
Balancing Equations
• We need to write balanced chemical equations represent chemical
reactions and the conservation of mass.
• For example: The equation below shows hydrogen and oxygen
making water but there are more oxygen atoms on the right than
the left.
H₂ + O₂ H₂O
• In the equation below there are 4 hydrogen atoms on the left
and right of the equation and 2 oxygen atoms on each side
2H₂ + O₂ 2H₂O
Compounds
• Compounds are 2 or more elements that are chemically bonded
• These are made in chemical reactions.
• Compounds are given a formula for example carbon dioxide is CO2 means 1
carbon atom and 2 oxygen atoms.
• Another example is calcium hydroxide Ca(OH)2 which means 1 calcium, 2
oxygen atoms and 2 hydrogen atoms
Chemical Reactions
• In some chemical reactions it may appear that there are less products than
there were reactants; however this is often because a gas has been made
and this has escaped into the atmosphere.
Pure and Impure Substances
• A pure substance contains only one type of element or compound.
• An impure substance contains more than one type of element or compound in a
mixture, for example salt water contains NaCl and H2O. All mixtures are impure
substances.
• Mixtures are much easier to separate than elements or compounds as they are not
chemically bonded
• There are a variety of ways that mixtures can be separated and they are outlined
below. Remember that these are all physical changes and chemical bonds are not
broken during any of these processes.
Pure
A substance made of only ONE type of element or
compound
The structure of the Atom
• All matter is made from atoms. Atoms are very small. The radius of atom is
about 1x10-10 m (this is also known as 0.1 nanometres).
• The central part of the atom is known as the nucleus. It is only 1x10-14m across,
which is 10,000 times smaller than the total atom.
• An atom is made up of three subatomic particles: protons, electrons and
neutrons.
• Protons and neutrons are found in the nucleus
• Electrons are found orbiting the nucleus in shells (also known as energy levels).
• The mass and charges of the sub atomic particles is shown below:
• Atoms have no overall charge because they have the same number of positive
protons as negative electrons.
Atomic Number and Mass Number
Mass number: This is the total of protons+neutrons
Atomic number: This is the number of protons
Therefore sodium has 11 protons, 11 electrons and 23-11= 12 neutrons
Key Terms - Definitions
Atom - The particles that make up all substances with mass, they
contain protons, neutrons and electrons.
Nucleus - The centre of an atom, it contains protons and neutrons.
Nanometre - A unit of measurement: 1x10-9m
Proton - A sub atomic particle found in the nucleus, it has a charge
of +1 and a relative mass of 1.
Electron - A sub atomic particle found in the shells of an atom, it has
a charge of -1 and a negligible mass
Subatomic - These are the smaller particles that make up an atom
Neutron - A sub atomic particle found in the nucleus of an atom, it
has a charge of 0 and a mass of 1
Atomic Number - The number of protons in an atom.
Mass Number - The total of protons and neutrons in an atom.
Electron Configuration
There are very strict rules about how electron fill up the
electron shells, the inner shell is always filled first. Each shell
has a maximum number of electrons it can take.
Shell 1: maximum 2 electrons
Shell 2: maximum 8 electrons
Shell 3: maximum 8 electrons
The electronic configuration of Sodium (Na) can also be written
like this 2,8,1. This shows there is 2 electrons in the 1st shell, 8
electrons in the second shell and 1 electron in the 3rd shell
Mixture
A mixture is two or more different atoms which are not
chemically bonded – can be separated
Compound
Two or more elements that are chemically bonded
Group
The columns on the Periodic Table
Period
The rows on the Periodic Table
Reactant
What you start with in a chemical reaction
Product
What is made in a chemical reaction
Impure
A mixture of elements and/or compounds
Chromatography
A technique where mixtures can be separated based on
their solubility.
Distillation
A separation technique which means a mixture of two
liquids is heated
Crystallisation
Method of mixture separation where a solvent is
evaporated, leaving the solute behind.
