STRUCTURE OF THE ATOM AND THE PERIODIC TABLE
( HIGH SCHOOL CHEMISTRY)
Simple Structure of the Atom
The are there are about 119 known elements
The following illustration shows the names and symbols of first 20 elements of
the periodic table.
Atoms are very small particles of an element, but they contain even smaller
particles called sub-atomic particles as follows;
• Protons - found in the nucleus, they are positively charged (+ve)
• Electrons - found in the nucleus, they are negatively charged (–ve)
• Neutrons - they can be imagined as circulating the nucleus in energy levels,
they have no charge
,In a neutral atom, Number of protons = Number of electrons
Particles present in an atom are summarized below.
Sub-atomic Particle Mass Charge Where found in atom
Proton 1 + (Positive) inside nucleus
Neutron 1 0 (Neutral) inside nucleus
Electron 1/1840 - (Negative) outside nucleus
Structure of the Atom
The various energy levels in an atom are represented by a series of circles sharing
the same centre (nucleus), separated from each other by roughly equal distances
, The nucleus of the atom is at the centre of the circles. The electrons in the energy
levels are represented by dots (.) or crosses (x). The energy levels are labelled 1st,
2nd, 3rd, 4th and so on starting from the one nearest to the nucleus as shown below;
The electrons that occupy the 1st energy level have lower energy than those in the
2nd energy level. Subsequently those in the 2nd energy level have lower energy than
those in the 3rd energy level and so on. The 1st energy level usually has a maximum
of two electrons while the 2nd energy level has a maximum of eight (8) electrons.
We can summarise the electrons, and their arrangement in each energy level as
shown in the table below.
( HIGH SCHOOL CHEMISTRY)
Simple Structure of the Atom
The are there are about 119 known elements
The following illustration shows the names and symbols of first 20 elements of
the periodic table.
Atoms are very small particles of an element, but they contain even smaller
particles called sub-atomic particles as follows;
• Protons - found in the nucleus, they are positively charged (+ve)
• Electrons - found in the nucleus, they are negatively charged (–ve)
• Neutrons - they can be imagined as circulating the nucleus in energy levels,
they have no charge
,In a neutral atom, Number of protons = Number of electrons
Particles present in an atom are summarized below.
Sub-atomic Particle Mass Charge Where found in atom
Proton 1 + (Positive) inside nucleus
Neutron 1 0 (Neutral) inside nucleus
Electron 1/1840 - (Negative) outside nucleus
Structure of the Atom
The various energy levels in an atom are represented by a series of circles sharing
the same centre (nucleus), separated from each other by roughly equal distances
, The nucleus of the atom is at the centre of the circles. The electrons in the energy
levels are represented by dots (.) or crosses (x). The energy levels are labelled 1st,
2nd, 3rd, 4th and so on starting from the one nearest to the nucleus as shown below;
The electrons that occupy the 1st energy level have lower energy than those in the
2nd energy level. Subsequently those in the 2nd energy level have lower energy than
those in the 3rd energy level and so on. The 1st energy level usually has a maximum
of two electrons while the 2nd energy level has a maximum of eight (8) electrons.
We can summarise the electrons, and their arrangement in each energy level as
shown in the table below.
