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Science revision Chemistry paper 1 (Atomic structure (Protons and neutrons…
Science revision Chemistry paper 1
Electrolysis
Decomposition of a liquid by passing an electric current through it
What electrolysis needs:
Electrolytes
The liquid that the electric current flows through
Negative electrodes (cathode)
Positive electrodes (anode)
Direct current power supply
Cations
Positively charged ions that are attracted to cathodes (negative electrodes)
recognise cations from their chemical formulae (+)
Anions
Negatively charged ions thare are attracted to anodes (positive electrode)
recognise anions from their chemical formulae (-)
Atomic structure
Everything is made out of atoms
Every atom is made of a nucleus consisting of protons and neutrons. Nucleus is surrounded by electrons.
Atoms have a neutral overall charge as it has the same number of electrons as protons
Protons and neutrons have the same mass
Protons have a charge of +1 and a mass of 1
Neutrons have a charge of 0 and a mass of 1
Electrons have a charge of -1 and a mass of 0.0005
The atomic number is the number of protons in an atom
The mass number is the total number of protons and neutrons in an atom
Elements are arranged in a periodic table in ascending order of atomic number
Chemical bonding
Covalent bonding
Pure covalent bonding
Atoms are held together by electrostatic forces of attraction between positively charged nuclei and negatively charged shared electrons
Polar covalent bonding
Most covalent compounds the bonding is polar covalent
Covalent bonds with unequal electron sharing are called polar covalent bonds
Atoms with the higher electron negativity will have a greater share of the electrons. This will result in the atom having a slight negative charge compared to the other atom which will have a slight positive charge
Ionic bonding
The electrostatic force of attraction between positively and negatively charged ions
Ions have been produced as a result of a transfer of electrons between two atoms with a large difference in electron negativities
Results from metals combining with non-metals. e.g. sodium (metal) combing with chlorine (non-metal)
