Alkalimetalle (Gesetzmäßigkeiten: wieso?)

Achja:
Dieses "&#8230" bedeutet nur drei Punkte(...)

hab hier noch was über "Periodic TRends" aussem Chemie Unterricht in Aussieland. Ist zwar englisch aber man kanns trotzdem verstehen denke ich ;)

Periodic Trends
Periodic Law: when the elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.

Periodic Trends in Atomic Size
Measured in Covalent Atomic Radii: half the distance between the nuclei of a homo-nuclear diatomic molecule
Down a group:
an extra principal energy level of electrons is added to the atom
an extra layer of inner electrons “shield” the outer electrons from the pull of the extra protons in the nucleus
atomic size increases

Across a Period:
One extra electron is added to the same principal energy level
the shield effect remains the same as no more principal energy levels are added
one proton is added to the nucleus, increasing the pull of the nucleus
atomic size decreases

Periodic Trends in Ionisation energy
First Ionisation energy – the amount of energy needed to remove an electron from a gaseous atom, therefore forming a positive ion.
The amount of energy needed to remove the next electron from a positive ion is called the second ionisation energy, and so on...

Down a group:
the outermost electron is further shielded from the pull of the nucleus
first ionisation energy decreases

Across a period:
Nuclear attraction increases
first ionisation energy increases

Periodic Trends in Electron Affinity
Electron Affinity:
the energy change associated with the addition of an electron to a gaseous atom to form a negative ion
most atoms release energy when gaining an electron, giving a negative change in energy
the more negative the number, the more easily the atoms accept an electron, the greater the electron affinity
a large negative number indicates are more stable ion
a positive electron affinity number indicates energy absorption with the addition of an electron

Down a group:
atomic size increases, therefore nuclear attraction decreases
electron affinity decreases

Across a period:
Atomic size decreases, nuclear attraction decreases
electron configuration approaches noble gas
Electron affinity increases

Periodic Trends in Ionic Size
Ions are always a different size than the original neutral atom
positive ions (cations) are smaller, negative ions (anions) are larger then the original atom

Down a group:
Ionic size increases

Across a period:
cation size decreases
anion size decreases from group 5

Periodic Trends in Electro negativity
Electro negativity:
ability of an atom to attract electrons to itself when chemically combined with another element
Arbitrary units: Pauling Electro Negativity scale
a higher electro negativity means the atom attracts shared electrons in the bond to itself, forming an anion
a smaller electro negativity means, the shared electrons will move away from the atom, forming a cation
Noble gases are excluded, as the do not form compounds

Down a group:
Electro negativity decreases

Across a period:
Electro negativity increases

Super! Fehlt mir bloß noch Siede-/Schmelztemperatur und Dichte!

Den langen Text les ich erstmal noch nich durch.. aber hol ich nach!

Danke danke :))

Noch jemand mit Erklärungen?

Ach, noch ne Frage! Gehört Wasserstoff nun zu den Alkalimetallen oder nicht?!

Irgendwie verwirrt mich das :p

auf der Seite die mir Püppi gezeigt hat steht nämlich "Die Gruppe der Alkalimetalle ist die 1. Hauptgruppe im Periodensystem der Elemente." ...
Also ganz sicher mit H?

Vielen Danke für deine/eure Bereitschaft übrigens :)

abgesehen davon: denk ma nach: Wasserstoff ein metall?!

hmm frag grad meinen Kumpel, der hat chemie LK der weiss es aber auch net... DEpp :D

oh ja sorry! Hatte son Periodensystem im Kopf, wo H ganz wo anders ist und habs dann wohl durcheinander gebracht :D

Aber uns fehlt immernoch die antwort auf die drei ersten punkte der frage :D

wenn du die meinst: …
dann waren das mal auflistungspunkte, die beim rüberkopieren von irgendwoher, nicht mitgekommen sind :D