Lecture 1 – Proton, Neutron & Electron

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 1	www.livescience.com

Atomic Structure:

Atom is the smallest particle of an element. It consists of a centralized nucleus containing Proton(s) and Neutron(s), while the Electron(s) revolve around the nucleus.

Figure 10:

Nucleus:

Nucleus is the central part of the atom. It contains proton and neutrons. It is positively charged in nature because of the presence of positively charged protons, present in it. It is the most important part of an atom and gives the atom its characteristic properties.

Neutron:

Neutron is an electrically neutral particle within the nucleus of an atom.

Proton:

Proton is a positively charged particle within the nucleus of an atom.

Proton and Neutron are relatively same in size.

Electron:

Electron is a negatively charged particle that revolves around the nucleus of an atom. It is the smallest particle with 1/1840 in size when compared to a proton or a neutron. That is 1840 electrons together have a mass of 1 proton or neutron.

Table 2 summarizes this:

Table 2:

	Proton	Neutron	Electron
Charge	Positive	Neutral	Negative
Mass	1	1

Electrons & their Orbits/Shells:

Electron revolve around the nucleus in their fixed paths called the Orbits or Shells. Each Orbit has a certain capacity to hold electrons. Table 3 shows the Orbits/Shells and their capacities.

Table 3:

Orbit/Shell Number	Name	Capacity (Max number of Electrons)
1	K	2
2	L	8
3	M	8
4	N	18

(Note: the actual capacities of M and N shells are different as stated above, but for the ease of understanding the Electronic Configuration concept, max capacity taken here is 8 and 18, respectively.) 

Electronic Configuration:

Electronic configuration is the arrangement of electrons in the orbits/shells according to its capacity.

For example:

1. Lithium has 3 electrons;
• 2 electrons fill the K-Shell
• while the remaining 1 electron will settle in the L shell 
• electronic configuration of Lithium is 2, 1. 
2. Sodium has 11 electrons; 
• 2 electrons fill the K shell, 
• while 8 fill the L shell, 
• the remaining 1 electron will settle in the M shell 
• electronic configuration of Sodium is 2, 8, 1

For an atom to be electrically neutral, the negative charge outside the nucleus (electrons) MUST balance the positive charge inside the nucleus (protons). Therefore, the number of electrons in an atom always equal the number of protons of the atom.