Bohr model (1913)

Particle Symbol Relative Charge Mass Unit
Electron e- -1 5.4858 x 10-4
Proton p+ +1 1.0073
Neutron n 0 1.0073

 

Protons = Electrons ⇒ Atom. Neutral.

Protons ≠ Electrons ⇒ Ion. Charged.

Electrons are surrounding the nucleus, consisting of protons and neutrons.

 

Element

Mass number are the number of protons and neutrons in the nucleus.

Atomic number are the number of protons in nucleus.

 

For example, 42He, where mass number is written on top left, and atomic number on bottom left.

 

Periodic Table

The elements are arranged in the order of increasing atomic number, from left to right, from up to down.

Each element has a unique atomic number (or the number of proton).

 

Electronic arrangement

The maximum number of electron that a shell can hold is 2(n)2

 

n max
1 2
2 8
3 18
4 32

 

Electronic configuration

There are subshells inside the shell.

Subshell Orbitals Max Name Quantum Number
n 1 2 s  Principal
l 3 6 px, py, pz Angular Momentum
m 5 10 dxy, dxz, dyz, dx2-y2, dz2 Magnetic
s 7 14   Spin