7) Periodicity Flashcards
Define group
vertical column in the periodic table
Elements in a group have _ and the same _
similar chemical properties
number of outer shell electrons
Define period
horizontal row of elements in the periodic table
Elements show _ across a period
a trend in properties
Define periodicity
a repeating trend in properties of elements across each period
Name the 4 block of the periodic table
s-block
p-block
d-block
f-block
Define first ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form 1 mole of gaseous 1+ ions
Give an equation for the first ionisation energy of Na
Na(g) -> Na+ (g) + e-
The first electron lost will be _ and will experience _
in the highest energy level
the least attraction from the nucleus
What is nuclear attraction and therefore, ionisation energy affected by?
atomic radius
nuclear charge
electron shielding
Define second ionisation energy
the energy required to remove 1 e- from each ion in 1 mole of gaseous 1+ ions of an element to form 1 mole of gaseous 2+ ions
Give an equation for the second ionisation energy of He
He+ (g) -> He2+ (g) + e-
What do successive ionisation energies provide important evidence for?
different energy levels
a large jump in ionisation energy marks a change from one shell to another
What is the trend in first ionisation energy down a group and why?
first ionisation energy decreases
atomic radius increases and shielding increases
What is the trend in first ionisation energy across a period and why?
first ionisation energy increases
nuclear charge increases
Define metallic bonding
the electrostatic attraction between positive metal ions (cations) and delocalised electrons
Define giant metallic lattice
3D structure of cations and delocalised electrons, bonded together by strong metallic bonds
Describe a giant metallic lattice
cations fixed in position
mobile delocalised e- (from each atoms’ outer shell)
Define giant covalent lattice
3D structure of atoms, bonded together by strong covalent bonds
Give 3 elements which form a giant covalent lattice
carbon
boron
silicon
Diamond has a _ structure and bond angles of _
tetrahedral
109.5
Do giant metallic lattices conduct electricity?
yes in solid and liquid states (electrons act as mobile charge carriers)
Do giant covalent lattices conduct electricity?
no except graphene and graphite
What two properties do giant metallic lattices and giant covalent lattices share?
high melting and boiling points
insoluble
Describe graphene and graphite
giant covalent structures of carbon based on planar hexagonal layers with bond angles of 120 degrees. This bonding only uses 3/4 outer electrons so the spare e- is delocalised
State the difference between graphene and graphite
graphene is a single layer of graphite whereas, graphite is made up of parallel hexagonal layers with weak London forces between
What does the sharp decrease in melting point across periods 2 and 3 indicate?
change from giant to simple molecular structures
Why does Si form a giant structure and not a simple molecular lattice?
because it is in group 4 - the same as carbon, so behaves in the same way and forms a giant covalent structure like diamond
