Module 3.1 The perodic table Flashcards
in the early 1800s what where the only two ways to categorise elements
- by their physical and chemical properties
- by their relative atomic mass
explain Dobereiner’s triads
he group elements with similar characteristics in threes and called them triads.
explain the law of octaves
Newlands order elements by mass and found similar elements appeared at regular intervals every 8th element was similar.
Mendeleev produced the first accepted version. what did his table contain
arranged elements by atomic masses.
left gaps where the next element didn’t seemed to fit.
he predicted the properties of undiscovered elements.
what do all elements in a period have in common
they all have the same number of electron shells (although not sub-shells)
period 1 has 1 electron shell and so on.
repeating trends in chemical and physical properties across the period due to this.
the trends that elements share in periods are known as
periodicity
what do all elements in the same group have in common
they all have the same number of electrons in their outer shell.
this causes them to also have similar CHEMICAL properties.
what does the group number tell you?
the number of electrons in the outer shell
s block elements contain which groups
groups 1 and 2
what is the outer shell electron configuration of elements in the s block
S(1) or S(2)
e.g Mg is 1s(2) 2s(2) 2p(6) 3s(2)
Li is 1s(2) 2s(2)
what part of the perodic table is the d block
the transition metals
what is the electron configoration of d block elements
outer shell is always a d sub shell
e.g cobalt: 1s(2) 2s(2) 2p(6) 3s(2) 3p(6) 3d(7) 4s(2)
(even though 4s fills first and so the last sub shell is 3d it is not written this way)
the p block contain which groups of elements
groups 3-7 and 0
what is the outer shell electron configurations of elements in the p block
from s(1)p(1) to s(2)p(6) e.g Cl: 1s(2) 2s(2) 2p(6) 3s(2) 3p(6)
period 1 can have what outer sub shell configeration
up to 1s(2)
period 2 can have what outer sub shell configeration
up to 2s(2) 2p(6)
period 3 can have what outer sub shell configeration
up to 3s(2) 3p(6)
ionisation is
the removal of one or more electrons
the first ionisation energy is
the energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms.
you put energy in to ionise an atom so it is an
endothermic process
give the equation of the first ionisation of oxygen
O(g) –> O+(g) + e-
the lower the ionisation energy
the easier it is to form an ion
factors affecting ionisation energy are (3)
- NUCLEAR CHARGE
- ATOMIC RADIUS
- SHIELDING
nuclear charge affects ionisation energy how?
the more protons there are in nucleus the more ve+ charged the nucleus is and the STRONGER THE FORCE OF ATTRACTION for the electrons
atomic radius affects ionisation energy how?
attraction falls off very rapidly with distance. an electron close to the nucleus will be much more strongly attracted than one further away.
shielding affects ionisation energy how?
as the no. of e- beteween outer e- and the nucleus increases the outer e- feel less attraction towards the nuclear charge.
a high ionisation energy means there is a
strong attraction between the e- and the nucleus so more energy is needed to overcome the attraction and remove the electron.
how does ionisation energy change as you go down a group
ionisation energy usually falls i.e it gets esier to remove outer electrons
ionisation energy decreases down a group because (2)
- ATOMIC RADIUS elements further down have more
electron shells. increasing atomic radius so outer
electrons are further away from nucleus - SHIELDING the extra inner shells shield the outer
electrons from the attraction of nucleus
-although protons ve+ charge increases so does the
electrons ve- charge so there is no effect
how does ionisation energy change as you go across a period
ionisation energy increases as you go across a period
why does ionisation generally increase as you go across a period (2)
- NUCLEAR CHARGE number of protons is increasing. as
ve+ of nucleus increases electrons are pulled closer
reducing ATOMIC RADIUS - extra electrons gained are added to the outer energy
level so don’t provide extra shielding effect
what are the 2 exceptions to the trends in ionisation energy on the period table?
- the drop between groups 2 and 3
- the drop between groups 5 and 6
why is there a drop in ionisation energy between groups 2 and 3
SUB-SHELL STRUCTURE
- outer electron in group 3 is in a p orbital rather than s
- p orbital has slightly higher energy than s in the same shell
- so electron is found further away from the nucleus
- these factors override the effects of the increasing nuclear charge resulting in ionisation energy dropping slightly
why is there a drop in ionisation energy between groups 5 and 6?
p ORBITAL REPULSION
- in group 5 elements the electron is being removed from a singly occupied orbital
- in group 6 elements the electron is being removed from an orbital containing 2 e-
- the repulsion between the 2 electrons means that the e- is easier to remove from shared orbitals.
what does successive ionisation energies involve
involves the removal of additional electrons
the equation for the 2nd ionisation of oxygen is:
O+(g) –> O2+(g) + e-
successive ionisation energies can show
the shell structure of an element
how does successive ionisation energies show shell structure
- within each shell, successive ionisation energies will increase as you are removing e- from increasingly +ve ion and there is less repulsion amongst remaining electrons
- big jumps in ionisation energy happen when a new shell is broken into as electron is being removed in a shell closer to the nucleus.
- this shows shells.
successive ionisation energies can also predict
electronic structure of an element.
by counting the no, of electrons removed before each big jump tells u how many e- are in each shell.
diamond, graphite and graphene are…
giant covalent lattices
what are giant covalent lattices
- huge networks of covalently bonded atoms.
- carbon atoms can form this type of structure because they can each form 4 strong covalent bonds
what are different forms of the same element in the same state called
allotropes
name and explain the properties of diamond (5)
- very high melting point due to strong covalent bonds
- diamond is the strongest known substance due to giant covalent lattice tetrahedral shape each carbon bonded to 4 others
- good thermal conductor. (vibrations travel easily)
- can’t conduct electricity (all outer electrons are held in localised bonds.
- it wont solved in any solvent
name a element with very similar properties to carbon and what it can form
silicon
- in same periodic group
- also forms crystal lattice with similar properties to carbon
- can form 4 strong covalent bonds
name and explain the properties of graphite (4)
- feels slippery:
weak forces between layers in graphite are easily
broken so that sheets can slide over each other. - conduct electricity:
delocalised electrons aren’t attached to any particular
carbon and are free to move along sheets. - very high melting point:
because of strong covalent bonds in hexagonal sheets - insoluble:
covalent bonds are too strong to break
describe the structure of graphene
is a sheet of carbon atoms joined in hexagons.
the sheet is one atom thick making it 2-dimesonal
describe and explain the properties of graphene (3)
- conducts electricity:
de-localised electrons free to move along the sheet. the single layer allows quicker movement above and below sheet making it the best known conductor
-extremely strong:
de-localised electrons strength covalent bonds
-transparent and light
due to it only being a single layer
metal can have giant structures called
giant metallic lattices structures.
describe how giant metallic lattices structures form (metallic bonding):
- e- in outer shell are delocalised leaving a +ve metal cation
- metal cations are electrostatically attracted to the delocalised e-.. they form a lattice of closely packed cations in a sea of delocalised electrons.