Unit 1 – P1, P2, M1, D1
The Periodic Table, Atomic Structure and Chemical Bonding
The periodic table
contains elements found
in our surroundings,
whether that’s in the air,
in the ground or
contained in objects and
materials etc. The
periodic table contains
many key features all of
which help determine
where they are placed
and how they are
relevant to those that
have similarities to
them.
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These key features are;
The elements. Without the elements the periodic table would have no use. “An element is a
substance that cannot be broken down into any other substance” [what are elements, 2019]. The periodic
table contains all the discovered elements today and has them ordered in groups with similar
properties. Metals are the most discovered elements in the periodic table at this present time. A few
properties of metals are that they are a good conductor of electricity and are solid at room
temperature e.g. titanium, nickel and gold – an exception is mercury which is a liquid state at room
temperature. The opposite to the metals are the non-metal elements which hold the opposite
properties of being bad conductors of electricity and are a gaseous state at room temperature e.g.
oxygen and chlorine – however there are exceptions to a few non-metals that are in fact a solid at
room temperature, such as sulphur and carbon, and bromine which is a liquid at room temperature.
The periodic symbol. Each element has an abbreviated form otherwise some elements and their
original name would be too long to fit onto one line. Chemical element symbols normally range from
one to two letters and are written using the Latin alphabet. For example, Potassium has the periodic
symbol K (Kalium in Latin) and Molybdenum has the periodic symbol Mo (Molybdaenum in neo-
Latin).
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, The atomic number. The atomic number has a few purposes, one of these is organising the elements
in the correct order so the number increases (a bit like a number line). The atomic number also has a
purpose which tells us exactly how many protons are in the atom of that element. As well as this, in
an atom the number of protons equals to the number of electrons. For example, Calcium (Ca), has
an atomic number of 20. This shows it is the 20 th element in the periodic table, it contains 20 protons
in the nucleus of its atom and therefore holds 20 electrons in the shells of its atom. Atoms have no
overall charge as protons are positively charged and electrons are negatively charged. These
opposing charges cancel each other out to create no overall electrical charge.
The relative atomic mass. The relative atomic mass tells us the mass of that element’s atom which is
approximately the same as the total number of protons and neutrons in the nucleus of the atom.
The small amount of mass gained from electrons is ignored in calculating the mass number. For
example, Sodium (Na) has a relative atomic mass of 23.0 (1dp), and so there’s a total of 23 protons
and neutrons in the nucleus of the atom. By being given the atomic number and relative atomic
mass we can work out exactly the number of electrons, protons and neutrons in an atom.
Calculating protons, neutrons and electrons. The atomic number gives us the number of protons
and the relative atomic mass gives us the total of protons and neutrons. But then how do we work
out the exact number of protons and neutrons? The atomic number shows the number of protons
which is equal to the number of electrons and so to work out the number of neutrons we take the
relative atomic mass and minus the atomic number. For example, Sulphur (S) has an atomic number
of 16 and a relative atomic mass of 32. The number of protons is 16 and so the number of electrons
is also 16. 32-16 which is 16, therefore gives us the number of neutrons
The periods. Periods are what organises the chemical elements from left to right (horizontal row).
There are 7 periods in the periodic table that are numbered on the left-hand side and in each period
the elements don’t have many similar properties. However, with periods and the organisation of the
elements, the atomic number increases by 1. Regarding the number of shells surrounding the
nucleus, all elements in the same row have the same number of shells. For example, both
Magnesium and Argon which are both in the 3 rd period have 3 shells surrounding the nucleus.
The groups. Groups are what also organises the elements but instead of left to right, they run from
top to bottom (vertical columns). There are 18 numbered groups in the periodic table and elements
in the same group have similar atomic structures and similar physical or chemical characteristics. An
example of one of the groups in the periodic table are the Alkali Metals which make up group one.
The group starts with Lithium and ends with Francium. All the elements contained in group 1 has 1
electron in their outermost shell. They also have very similar chemical properties, increasing in
reactivity the further down you go, they all react vigorously with water and some elements even
explode on contact, due to this they are stored in oils.
The periodic trends. The trends are patterns that occur in the properties of elements in the periodic
table. There are numerous periodic trends, but the four key ones are; metallic character, ionisation,
atomic radius and electronegativity.
o The metallic character “Metallic character is the name given to
the set of chemical properties associated with elements that are
metals” [Helmenstine, 2018]. These chemical properties result from
how easily it is for an atom to lose an electron to form a
positively charged ion. The metallic character decreases as you
go across the periods of the periodic table (left to right). This is
because as you go along, each atom gains another electron
which means there’s more electrons for the atom to lose. An
