GCSE Chemistry Paper 2 Notes
Chemistry Basics
Atom: The smallest neutral part of an element that can take part in chemical reactions.
Ion: A charged particle formed when an atom, or group of atoms, loses or gains electrons.
Element: A substance made from atoms with the same
unique atomic number [number of protons in the nucleus].
Diatomic Elements: The formula for most elements is just
their symbol, but there are some non-metal elements known
as diatomic elements. They contain 2 atoms of the same
element covalently bonded together.
Molecule: A particle consisting of 2 or more atoms
covalently bonded together.
Compound: Contain 2 or more different elements
chemically joined together.
Isotopes
Isotopes are atoms of an element with:
The same number of protons.
Different
number of neutrons.
So they have the same atomic number but a different mass
number.
Isotopes of an element have the same chemical properties
because they have the same number of electrons.
Ions
An ion is an atom or a group of atoms with a (+) or (-) charge.
In general:
Hydrogen atoms and metal atoms lose electrons to form positively charged ions [cations].
Non-metal atoms gain electrons to form negatively charged ions [anions].
Oppositely charged ions in solution may join to form an insoluble solid, called a precipitate.
In all ionic equations:
All substances are shown by their formulae.
The number of atoms of each element in the reactants and products are the same.
The total electrical charge is the same on both sides of the equation.
Spectator ions: Ions that are present during the reaction but remain unchanged [so don’t change state].
,Mendeleev’s Table
Dimitri Mendeleev’s periodic
table was successful and
developed into the modern
periodic table.
In 1869, he arranged all the
elements known at the time into
a table.
The Periodic Table
The modern periodic table is useful for describing and predicting the properties of elements.
Atomic number:
o In Mendeleev’s periodic table, atomic number was just the position of an element in the table.
o Later discoveries showed that:
Atomic number is usually the number of protons in an
atom’s nucleus.
Each element has a unique atomic number.
If the elements are arranged in order of increasing
atomic number, Mendeleev’s pair reversals are
explained.
, Electronic Configuration
An electronic configuration describes the arrangement of
electrons in shells in an atom or ion.
In an atom:
o Electrons occupy electron shells.
o Shells are filled, starting with the innermost shell.
o Different shells hold different maximum numbers of electrons.
Metals
Most elements are metals, and are placed on the left-hand side of the periodic table.
Copper is also
ductile. It can be
pulled to make
wires without
breaking. This is
because its layers
of positive irons
can slide over
each other
Chemistry Basics
Atom: The smallest neutral part of an element that can take part in chemical reactions.
Ion: A charged particle formed when an atom, or group of atoms, loses or gains electrons.
Element: A substance made from atoms with the same
unique atomic number [number of protons in the nucleus].
Diatomic Elements: The formula for most elements is just
their symbol, but there are some non-metal elements known
as diatomic elements. They contain 2 atoms of the same
element covalently bonded together.
Molecule: A particle consisting of 2 or more atoms
covalently bonded together.
Compound: Contain 2 or more different elements
chemically joined together.
Isotopes
Isotopes are atoms of an element with:
The same number of protons.
Different
number of neutrons.
So they have the same atomic number but a different mass
number.
Isotopes of an element have the same chemical properties
because they have the same number of electrons.
Ions
An ion is an atom or a group of atoms with a (+) or (-) charge.
In general:
Hydrogen atoms and metal atoms lose electrons to form positively charged ions [cations].
Non-metal atoms gain electrons to form negatively charged ions [anions].
Oppositely charged ions in solution may join to form an insoluble solid, called a precipitate.
In all ionic equations:
All substances are shown by their formulae.
The number of atoms of each element in the reactants and products are the same.
The total electrical charge is the same on both sides of the equation.
Spectator ions: Ions that are present during the reaction but remain unchanged [so don’t change state].
,Mendeleev’s Table
Dimitri Mendeleev’s periodic
table was successful and
developed into the modern
periodic table.
In 1869, he arranged all the
elements known at the time into
a table.
The Periodic Table
The modern periodic table is useful for describing and predicting the properties of elements.
Atomic number:
o In Mendeleev’s periodic table, atomic number was just the position of an element in the table.
o Later discoveries showed that:
Atomic number is usually the number of protons in an
atom’s nucleus.
Each element has a unique atomic number.
If the elements are arranged in order of increasing
atomic number, Mendeleev’s pair reversals are
explained.
, Electronic Configuration
An electronic configuration describes the arrangement of
electrons in shells in an atom or ion.
In an atom:
o Electrons occupy electron shells.
o Shells are filled, starting with the innermost shell.
o Different shells hold different maximum numbers of electrons.
Metals
Most elements are metals, and are placed on the left-hand side of the periodic table.
Copper is also
ductile. It can be
pulled to make
wires without
breaking. This is
because its layers
of positive irons
can slide over
each other
