NCEA Level 1 Chemistry (90172) 2009 — page 1 of 2
Assessment Schedule – 2009
Chemistry: Describe atomic structure and bonding (90172)
Evidence Statement
Q
ONE
(a)
(b)
Evidence
Achievement
Achievement with
Merit
Achievement with
Excellence
Isotopes are atoms of the same element that
have different masses / mass numbers /
numbers of neutrons in their nuclei.
THREE correct,
must be from at least
2 parts (a), (b), (c).
THREE correct,
must be one from
each of (a), (b),
(c).
Correctly defines
the term isotope
Carbon-12 has an atomic structure made up
of 6 protons, 6 electrons and 6 neutrons.
Carbon-13 and carbon-14 also have 6
protons and 6 electrons, but C-13 has 7
neutrons and C-14 has 8 neutrons.
Correctly defines the
term isotope.
Methane
Carbon monoxide
(c)
The particles in methane are molecules.
The particles are held together by weak
intermolecular forces / bonds. It takes very
little energy to break these forces. This
results in the low melting point.
The particles in calcium carbide are ions.
They are held together in a lattice by strong
ionic bonds. These bonds require a lot of
energy / are harder to break. This results in
the high melting point.
The different melting points of these two
carbon-containing substances occur because
of their different forms of bonding.
OR
Correctly identifies the
full atomic structure of
2 of the carbon
isotopes / correct
number of neutrons for
3 isotopes.
OR
Correctly draws one
Lewis Diagram.
OR
Correctly names the
particles in each
substance.
OR
Correctly names the
type of bonding
between particles in
each substance.
OR
Correctly names
particles and bonding
for one substance.
Correctly defines
the term isotope.
OR
Correctly identifies
the full atomic
structure of 2 of the
carbon isotopes /
correct number of
neutrons for 3
isotopes.
AND
Correctly draws
one Lewis diagram.
AND
Links type of
particle AND type
of bonding for
ONE substance, to
melting point /
energy to break
bond.
AND
Correctly identifies
the atomic
structure of 2 of
the carbon isotopes
/ correct number of
neutrons for 3
isotopes
AND
Correctly draws
Lewis Diagram for
carbon monoxide
AND
Discusses type of
particle AND type
of bonding for
BOTH substances
in relation to each
of their melting
points / energy to
break bonds.
NCEA Level 1 Chemistry (90172) 2009 — page 2 of 2
TWO
(a)
(b)
Fluorine and chlorine both have 7 valence
electrons / are both in Group 17.
F: 2,7
Cl: 2,8,7
Gives correct
electron
configurations for all
4 elements
Neon and argon both have a full valence shell
/ are both in Group 18.
Ne: 2,8
Ar: 2,8,8
OR
Describes F and Cl as
reactive AND Ne and
Ar as unreactive
Neon and argon both have full valence shell /
are already stable so both are unreactive.
Fluorine and chlorine, however, are not stable
/ they both require 1 electron to become
stable. This makes them both very reactive.
OR
Correctly explains
the boiling and
melting points /
energy to break
bonds of
EITHER
Ne or Cl.
The intermolecular forces between neon
atoms are small / weak. (The amount of
energy required to break the attractive forces /
to change state is small.)
Solid MgCl2 is ionic (magnesium is present as
magnesium ions, Mg2+, and chlorine is
present as chloride ions, Cl–). These ions are
held tightly in an ionic lattice when solid,
there is no movement of ions, and so solid
MgCl2 does not conduct electricity.
In molten MgCl2, the chloride and
magnesium ions are free to move. Since
current is carried by charged particles that are
free to move, molten MgCl2 can conduct
electricity.
In gaseous chlorine, the chlorine atoms form
molecules of Cl2. Molecules are not charged
particles so cannot carry an electric current.
Though the chlorine molecules are free to
move, chlorine gas is not a conductor of
electricity.
AND
Correctly links the
boiling and melting
points / energy to
break bonds of
EITHER
Ne or Cl.
OR
All (a) correct
Gives correct
electron
configuration AND
makes links to the
reactivity for Cl,F
AND Ne,Ar.
Must state that F, Cl
both require 1
electron.
AND
Correctly discusses
the boiling and
melting points /
energy to break
bonds of
BOTH
Ne and Cl.
OR
All (b) correct.
The intermolecular forces between chlorine
molecules are larger / stronger than for neon.
(The amount of energy required to break the
attractive forces / to change state is more than
neon.)
THREE
Gives correct
electron
configuration AND
makes links to the
reactivity for F, Cl
OR Ne, Ar.
Must state that F,
Cl both require 1
electron.
Describes 1 point
Links 2 points
Discusses 3 points
Conductivity of ONE
of: MgCl2(s) /
MgCl2(l) / Cl2(g)
described in relation
to particles.
Conductivity of
TWO of: MgCl2(s)
/ MgCl2(l) / Cl2(g)
fully described and
linked to particles.
Conductivity of
THREE: MgCl2(s),
MgCl2(l),Cl2(g)
discussed in relation
to particles.
Must show
understanding of how
electricity is
conducted (electrons
carrying charge
negates)
Must show
understanding of
how electricity is
conducted
(electrons carrying
charge negates)
Must show
understanding of
how electricity is
conducted
(electrons carrying
charge negates)
Must state molecules
for Cl2 and ions /
ionic substance for
MgCl2.
Must state
molecules for Cl2
and ions / ionic
substance for
MgCl2.
Must state
molecules for Cl2
and ions / ionic
substance for
MgCl2.
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
2A
2M+1A
2E+1M
OR
2E