Chemistry Reference
In-Depth Information
Questions
1
Explain the terms:
a
malleable
b
ductile.
2
Explain why metals are able to conduct heat and
electricity.
3
Explain why the melting point of magnesium (649 °C) is
much higher than the melting point of sodium (97.9 °C).
4
Suggest reasons why plastics and ceramics are used to
manufacture handles for metallic cooking utensils.
close-packed
hexagonal structure
(e.g. magnesium,
density
1.74 g cm
3
)
face-centred
cubic structure
(e.g. copper,
density
8.92 g cm
3
)
Figure 3.43
Relating different structures to the density of metals.
body-centred
cubic structure
(e.g. iron,
density
7.87 g cm
3
)
Checklist
After studying Chapter 3 you should know and understand the
following terms.
•
Ionisation
The process whereby an atom gains or loses an
electron(s) to become an ion.
•
Isotopes
Atoms of the same element which possess
different numbers of neutrons. They differ in nucleon number
(mass number).
•
Lattice
A regular three-dimensional arrangement of
atoms/ions in a crystalline solid.
•
Mass spectrometer
A device in which atoms or molecules
are ionised and then accelerated. Ions are separated
according to their mass.
•
Metallic bond
An electrostatic force of attraction
between the mobile 'sea' of electrons and the regular array
of positive metal ions within the solid metal.
•
Neutron
A fundamental, uncharged sub-atomic particle
present in the nuclei of atoms.
•
Nucleon number (mass number)
Symbol
A
. The total
number of protons and neutrons found in the nucleus of an
atom.
•
Nucleus
Found at the centre of the atom, it contains the
protons and neutrons.
•
Oxidising agent
A substance that causes an increase in
oxidation number.
•
Oxidation
The process of removing an electron or
electrons from an atom to create a positive ion. Gives an
increase in oxidation number.
•
Proton
A fundamental sub-atomic particle which has a
positive charge equal in magnitude to that of an electron.
Protons occur in all nuclei.
•
Proton number (atomic number)
Symbol
Z
. The
number of protons in the nucleus of an atom. The number
of electrons present in an atom. The order of the element
within the Periodic Table (p. 136).
•
Radioactive
A property of unstable isotopes. They
disintegrate spontaneously to give off one or more types of
radiation.
•
Radioisotope
A radioactive isotope.
•
Reducing agent
A substance that causes a decrease in
oxidation number.
•
Reduction
The process of adding an electron or electrons
to an atom to create a negative ion. Gives a decrease in
oxidation number.
•
Allotropy
The existence of an element in two or more
different forms in the same physical state.
•
Atomic mass unit
Exactly
1
12
of the mass of one atom of
the most abundant isotope of carbon-12.
•
Ceramics
Materials such as pottery made from inorganic
chemicals by high-temperature processing. Other modern
ceramics include zirconium oxide and silicon nitride.
•
Covalent bond
A chemical bond formed by the sharing
of one or more pairs of electrons between two atoms.
•
Delocalised
Refers to spreading out of electrons within
the metal structure.
•
Electron
A fundamental sub-atomic particle with a
negative charge present in all atoms within energy levels
around the nucleus.
•
Electron energy levels (shells)
The allowed energies of
electrons in atoms.
•
Electronic structure (confi guration)
A shorthand
method of describing the arrangement of electrons within
the energy levels of an atom.
•
Electrostatic force of attraction
A strong force of
attraction between opposite charges.
•
Giant ionic structure
A lattice held together by the
electrostatic forces of attraction between ions.
•
Giant molecular or macromolecular substance
A
substance containing thousands of atoms per molecule.
•
Glass
A supercooled liquid which forms a hard, brittle
substance that is usually transparent and resistant to
chemical attack.
•
Intermolecular bonds
Attractive forces which act
between molecules, for example van der Waals' forces.
•
Intramolecular bonds
Forces which act within a
molecule, for example covalent bonds.
•
Ion
An atom or group of atoms which has either lost one
or more electrons, making it positively charged, or gained
one or more electrons, making it negatively charged.
•
Ionic (electrovalent) bond
A strong electrostatic force of
attraction between oppositely charged ions.
