1. What does an atom looks like? What are the sub-atomic particles inside it.....(talk about electrons, neutrons, protons, electron shells, nucleus....)

Atoms are made up of three basic particles (sub-atomic ): protons, neutrons and electrons.

The properties of the three particles are shown in the table below:

Sub-atomic Particles	Relative Mass
Electron	1 / 1840
Proton	1
Neutron	1

The structure of an atom:





THe composition of protons, neutrons and electrons in an atom can be determined from its proton number ( atomic number)and nucleon number (mass number).
The proton number is defined as the number of protons in an atom.
The nucleon number is defined as the total number of protons and neutrons in the atom.
Since an atom is electronically neutal, number of protons should be equal to number of electrons in the atoms.
An atom cann be written with a symbol. Example:




MEANING:

1. The atom is sodium
2.Has 11 protons and electrons
3.Nucleon(mass)number of 23 (neutrons+ protons)
4. Has(23-11=) 12 neutrons

The way in which electrons are arranged in an atom among the various energy shells is called its electron configuration.
Each shell cann only hold up to a certain number of electrons
And each shell must be completely filled before going to the next level.
Examples:





Note that:

Protons and Neutrons are found in the nucleus

Electrons are found in the electron shell.

An electron is negatively charged while a proton is positively charged.


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