Atomic theory and the periodic table

• Scheikunde
• Middelbare school
• vwo
• Leerjaar 4

The periodic table of elements

Learning Goals

• You can describe and use Bohr's atomic model to draw an atom.
• You can explain the structure and purpose of the periodic table of the elements (PTE).
• You can identify alkali metals, halogens and noble gasses in  the periodic table.
• You can explain the properties of elements with respect to chemical reactions from their positions in the PTE.

Atomic models (What's in an atom?)

Dalton                                      Rutherford                             Bohr

Atoms have discrete masses (u) and charges (e), inner workings are unknown

Atoms have a tiny nucleus, which is (+)-charged, around it is a "cloud" of orbiting electrons (-)

Atomic nuclei consist of protons (+) and neutrons (0), surrounded by electrons(-) in fixed orbits ("shells")

What do we care about in chemistry?

• Atomic number = number of protons (this determines the atom's name, and these are the numbers of atoms in the PTE)
• Atomic mass = Number of nucleons (protons + neutrons) (

• For uncharged atoms (so, non-ions), number of electrons = number of protons.

Take Fluorine for example...

Group = column

Period = Row

Alkali metals 

• Group 1 of the PTE
• Extremely reactive!!

Alkali metals 

• Meet Sodium (Na)
• Has 1 electron in the outer shell (as do all alkali metals)
• Since full outer shells are the most stable: How can sodium achieve a full outer shell?
  

By relinquishing 1 electron!

Halogens

• Group 17
• Also extremely reactive!
  (But with a twist...)

Halogenen

• Fluorine is a halogen;
• It, too, wants a full outer shell...

By stealing 1 electron! (Sodium's!) 

Op de atoombinding komen we later nog terug. 

Or...by sharing an electron with a neighbor!

Shared pair of electrons = "atomic bond"

Op de atoombinding komen we later nog op terug. 

Noble gasses

• Group 18 of the PTE
• They want nothing to do with the rest... snobs!

Noble gasses 

• Meet Neon
• Like all noble gasses it has a full outer shell
• Which is extremely favorable, so there's no chemistry here...