Made by : Dr. Niveen Fawzy Revision on the atomic structure of
an atom
Slide 2
Chemical symbols of elements Some famous symbols
ElementSymbolElementSymbol HydrogenHSulphurS HeliumHeSiliconSi
CarbonCMagnesiumMg CalciumCaBromineBr ChlorineClLithiumLi
IodineINitrogenN ArgonArFluorineF AluminumAlOxygenO
PhosphorusPNeonNe ElementSymbol ZincZn SilverAg GoldAu CopperCu
IronFe SodiumNa PotassiumK MercuryHg LeadPb
Slide 3
Atomic construction An atom consists main of two parts:
1-NUCLEUS 2-ENERGY LEVELS First: Nucleus: First: Nucleus: Its the
central core of an atom The mass of an atom is concentrated in it
Contains: 1-PROTONS 2-NEUTRONS GR: The nucleus is positively
charged Second: Energy levels: Level symbolKLMNOPQ Level number
(n)1234567
Slide 4
Second: Energy levels: They are imaginary regions around the
nucleus in which electrons move according to their energies The
maximum no. of energy levels is 7 Each level has a certain amount
of energy increases by increasing the distance from the nucleus.
Level (k) has the least energy, while level (Q) has the highest
energy The no. of protons the no. of electrons, so the atom is
electrically neutral The no. of neutrons can be equal or more than
no. of protons except in hydrogen it doesnt contain neutrons Points
of comparison protonneutronelectron 1-Position:In the nucleus
Around the nucleus in energy levels
2-Charge:positiveneutralnegative 3-Mass:v.Large compared to
electron mass Very small
Slide 5
The no. of protons the no. of electrons, so the atom is
electrically neutral The no. of neutrons can be equal or more than
no. of protons except in hydrogen it doesnt contain neutrons Atomic
number & mass number Atomic no. no. of protons no. of electrons
Mass no. no. of protons no. of neutrons No. of neutrons mass no.-
atomic no. REMEMBER: The mass of the atom is concentrated in the
nucleus
Slide 6
Slide 7
Electronic configuration
Slide 8
The chemical activity is related to the no. of electrons in the
outer level : 1- If less than 8 electrons in outermost level active
atom, enter chemical reactions, like active gases 2- If saturated
by 8 electrons in the outermost level inactive atom, dont enter
chemical reactions, like noble gases Electronic configuration &
chemical activity
Slide 9
Atoms of active elements take part in the chemical reactions To
produce stable molecules Noble gases dont enter chemical reactions
Because the outermost energy levels are completely filled with
electrons N.B The electrons in the outermost energy level are
responsible for chemical reaction Give reason
Slide 10
Slide 11
Comparison between active & noble gases Active gasesNoble
gases Have less than 8 electrons in the outermost level The
outermost level is completely filled with 8 electrons (except He)
Take part in chemical reactions Diatomic molecule Dont take part in
chemical reactions Monoatomic molecule
