Chemistry: Chapter 5 - Atomic Structure

5.1 Inside Atons
Atoms are made up of protons, neutrons and electrons.

 Electrons:

• Carries one negative electric charge -1
• Has a relative mass of 1/1840

Protons:

• Carries one positive electric charge +1
• Has a relative mass of 1

Neutrons:

• Carries no electric charge
• Has a relative mass of 1

5.2 The Proton Number and Nucleon Number
Proton number + Nucleon number = Nucleon number

5.3 Isotopes
Isotops are atoms of the same element with the same number of protons but different number of neutrons.

5.4 Arranging Electrons in Atoms
First shell

• Hold a maximum number of 2 electrons.
• Is always filled first.

Second, third and sebsequent shells

• Can hold up to 8 electrons each.
• Are filled in order. Second shell must be filled before going to third, fourth shell.

The way the electrons are arranged in an atom is called electronic structure or electronic configuration.
The shell that is furthest from the nucleus is called the outer shell or the valence shell.
The electrons in this shell are called valence electrons.