periodicity 8 Flashcards
periodic table
order of increasing atomic number
can predict the properties depending on its position
groups
- the vertical column of elements
- similar chemical properties
- same number of electrons
reactivity
s-block metals = get more reactive going down the group
transition metals = non-reactive
periods
-horizontal rows
placing hydrogen
-forms a 1+ ion but not chemically similar and is also a gas
placing helium
-not a p-block element 1S2
group 1,2,3 elements bonding
giant structure
ionic compounds
metallic bonding
group 4 elements bonding
four covalent bonds (giant covalent)
group 5,6,7 elements bonding
non-metals
covalent bonds
group 0 (8) element bonding
noble gas
full outer shell
unreactive
melting and boiling point
1 - group 4
2- group 3,2,1
3- group 6,5,7
4-group 8
atomic radii
taken to be half the distance between the centres of a pair of atoms
the size of the atom ……. going across a period
decrease
radii of the atoms increase down a group
going down a group an extra shell of electrons are added, the electron is further away from the nucleus
why does the first ionisation energy increase across a period
a number of protons in the nucleus increases but the electrons enter the same shell. so it gets increasing difficult to remove an electron
why does the first ionisation energy decrease going down a group
the number of filled inner shells increase down the group, this means that there is an increase in shielding.
the electron is further away from the nucleus so it’s easier to remove
why there is a drop in ionisation energy from one period to the next
the new main level starts and so there is an increase in atomic radius, the outer electron is further from the nucleus so less strongly attracted to its easier to remove
drop in first ionisation energy between group 2 and 3
p-electron is already in a higher energy level than the s-electron, so it takes less energy to remove it
drop in first ionisation energy between groups 5 and 6
an electron in a pair will be easier to remove that one in an orbital on its own because it is already being repealled by the other electron
Bonding ( period 3)
Metallic - Na, Mg,Al
Giant covalent - Si
Covalent - P,S,Cl,Ar
Structure ( period 3)
Giant metallic - Na,Mg,Al
Giant covalent - Si
Molecular - P4, S8, Cl2
Noble gas - Ar
Atomic radii
Tells us the size of the atoms
Half the distance between the centres of a pair of atoms is used
Radius differs depending on what type of bonding
Decreases across a period ( theres a jump when starting the next period)
Why the radii of atoms decrease across a period
Add a proton ( increase nuclear charge)
Increased charge pulls the electron in closer to the nucleus
No more shielding from next shells
First ionisation energies
The enrgy required to convert 1 mole of gaseous ions into one mole of +1 gaseous ions
first ionisation energy increases across a period
because more protons are added to the nucleus however no more shells are adding meaning there is no extra shielding. therefore it is harder to move an electron so the ionisation energy is more
first ionisation energy drops as you go down a group
there is an increase in atomic radius and the outer electron is further away from the positive nucleus and so is easier to remove
periodicity
the regular recurrence of the properties of elements when they are arranged in atomic number order as the periodic table
classification
An element is classi ed as s, p, d or f block according to its position in the Periodic Table, which is determined by its proton number
