3.1. The atomic model Lesson 1

• Chemistry
• Middelbare school
• havo, vwo
• Leerjaar 3

 3.1. The atomic model

3. The structure of substances

The Atomic Model Learning Objectives

3.1.1 You can describe the structure of an atom.

3.1.2 You can use the concepts atomic number, mass number and isotope.

3.1.3 You can describe the layout of the periodic table.

3.1.4 You know what groups the halogens and noble gases belong to.

3.1.5 You know that elements can be categorized into metals and non-metals and basically how they are distributed in the periodic table.

From large to small:

protons are missing, they live in the nucleus and have a 1+ charge

Molecules are made from atoms

Atoms contain even smaller particles:

In the nucleus:

• protons
• neutrons

Around the nucleus:

• electrons

The atomic number of an atom = the number of protons

The electrons move around at a distance in so-called electron shells.

Electron shells:

shell	maximum number of electrons
K	2
L	8
M	18

The masses of the atomic building blocks:

Particle:	Location	charge	mass (unit)
proton (p + )	nucleus	1+	1,0 u
neutron (n 0 )	nucleus	0	1,0 u
elektron (e - )	electron cloud	1-	´negligible´

1 u (atomic mass unit) = 1.66 x 10-27 kg

Atomic number = number of protons

The number of protons in an atomic nucleus is equal to the atomic number. Every atom type (element) in the periodic table has it's own unique atomic number.  

The atomic number of iron  Fe = 26, so every Fe atom

has 26 protons in its atomic nucleus.

If you know the atomic number, you also know the number of 

electrons surrounding the nucelus, since this number has to be

the same as the number of protons. So a neutral iron atom 

contains 26 electrons. 

protons = electrons since neutral!

Atomic n

Atomic number: 

Number of protons (p+)

Mass number (u):

The sum of protons and neutrons:

p+ + n0

Isotopes:

Atoms of the SAME element with a different number of neutrons n0

Period →

Group ↓Text

Non-metals 

In their solid state:

• Dull (not shiny)
• Easy to break
• No/low conduction of heat and electricity

Group 18 (noble gasses)

Edelgassen

Group 17 (halogens)

Halogens

Metals

• shiny when polished
• malleable and or ductile
• conduct heat
• conduct electricity
• solid phase at room temperature (except Hg)