Matter and Materials Flashcards
(reduced definitions)
Pauli’s Exclusion Principle
Only two electrons can occupy an orbital and these must spin in opposite directions.
Hund’s Rule
No pairing in P orbitals before there is at least one electron in each of them.
Relative Atomic Mass
The mass of a particle on a scale where an atom of carbon-12 has a mass of 12.
Isotopes
Atoms of the same element having the same number of protons (atomic number) but different numbers of neutrons (mass number.)
Why are relative atomic masses for most elements NOT whole numbers?
The relative atomic masses indicated on most periodic tables are weighted averages of the various isotopes of elements.
Chemical Bond
A mutual attraction between two atoms resulting from the simultaneous attraction between their nuclei and the outer electrons.
Covalent bond
The sharing of electrons between atoms to form molecules. (NM-NM)
Molecule
A group of two or more atoms that are covalently bonded and that function as a formula unit.
Ionic Bonding
The transfer of electrons to form cations (positive ions) and anions (negative ions) that attract each other to form a formula-unit
Metallic Bonding
The bond between positive ions and delocalised valence electrons in a metal
Lone pairs:
2 electrons in the same orbital/ suborbital
Formula unit:
The structure formed when a cation and an anion form a bond.
A crystal lattice:
An orderly three-dimensional arrangement of particles in a solid structure
structure of sodium chloride crystal:
In the crystal:
each sodium ion is surrounded by six chloride ions to form a cubic structure. Each chloride ion is also surrounded by six sodium ions.
Valence electrons:
(outer electrons)
Electrons in the highest energy level of an atom in which there are electrons
ion:
A charged particle made from an atom by the loss or gain of electrons.
anion:
(negative ion) charged particle made from an atom by the gain of electrons
cation
(positive ion) positively charged ion made from an atom by the loss of electrons
(metallic bonding)
Conduction of heat and electricity
The free-moving valence electrons act as carriers of heat and electricity.
(metallic bonding)
Malleability and ductility
When metals are hit with a hammer, the positive ions shift over each other, but the delocalised electrons move between and prevent the positive ions from getting too close and then repelling each other. This stops the metal from breaking.
(Metallic bonding)
High density
Metal ions can be packed very close together, because elements are very small.
(metallic bonding)
Metallic lustre
Delocalised valence electrons can absorb and give back light of any frequency easily which causes metals to have a shiny appearance.
Pure substance
A substance that cannot be separated into simpler components by physical methods
Element
A pure substance consisting of one type of atom.
Compound
A pure substance consisting of two or more different elements
Mixture
A physical combination of two or more substances, where these substances are not bonded to each other.
Diffusion
The movement of atoms or molecules from an area of higher concentration to an area of lower concentration.
Brownian Motion
The random movement of microscopic particles suspended in a liquid or gas, caused by collisions between these particles and the molecules of the liquid or gas.
Freezing point
The temperature at which a liquid changes to a solid by the removal of heat.
Melting point
The temperature at which a solid, given sufficient heat, becomes a liquid
Boiling point
The temperature at which the vapour pressure of a substance equals atmospheric pressure
Melting
The process during which a solid changes to a liquid
Evaporation
The change of a liquid into vapour at any temperature below the boiling point.
freezing
the process during which a liquid changes to a solid by the removal of heat.
sublimation
the process during which a solid changes directly into a gas without passing through an intermediate liquid phase.
condensation
The process during which a gas or vapour changes to a liquid, either by cooling or by being subjected to increased pressure.
Temperature
The temperature of a substance is a measure of the average kinetic energy of the particles.
The kinetic molecular theory:
- Matter consists of small particles
- Particles are in constant motion
- Forces of attraction between particles
- Particles collide & exert pressure
- temp: measure of av kinetic energy of particles
- A phase change may occur when the energy of particles change
Heating curve:
Graph showing the change in temperature over time when a substance is being heated.
Cooling curve:
Graph showing the change in temperature over time when a substance is being cooled.
Why temp doesn’t change in phase change?
During a phase change the energy absorbed/ released does not go into increasing/ decreasing the average kinetic energy of the particles (hence no temp change) , rather goes into weakening/ strengthening the strength of the intermolecular forces between the particles.
what is this type of heat called?
(change the state of a substance without changing its temperature)
LATENT heat
