Physical sciences Semester 1 definitions:

Scientific skills, Chemistry, Electricity and Vectors

Atom

the smallest unit of an element that still retains the properties of that element

Ion

An atom or group of atoms that has gained or lost electrons and therefor carries a charge

Molecule

A group of two or more non-metal atoms which have been covalently bonded together that has no overall charge

Atomic radius

The distance from the nucleus of an atom to the outermost electron shell.

Ionisation Energy

The energy required to remove one electron from the outermost energy level

Electronegativity

a measure of the tendency of an atom to attract a bonding pair of electrons

Ionic bond

a transfer of electrons to form cations and anions which are electrostatic ally attracted in a crystal lattice

Valency

A number which indicated how many bonds (ionic or covalent) that atoms of an element can form

Covalent Bond

a sharing of at least one pair of electrons by two atoms

Metallic bonding

the attraction between positive kernels and a sea of delocalized electrons

Aufbau principle

Electrons enter the lowest energy orbital of the lowest energy fist

Hund’s rule

No electron pairing takes place in p,d or f-orbitals until all orbitals are occupied singly first

Pauli’s Exclusion principle

No orbital can contain more than two electrons. When two electrons are present in one orbital, they must have opposite spin.

Orbitals

Those permitted spaces in the different

energy levels where the probability of finding

electrons is great

Isotopes

Atoms of the same element that have the same

number of protons but a different number of

neutrons

Scalars

a physical quantity that has magnitude only

Vectors

a physical quantity that has both magnitude and direction

Resultant Vectors

the single vector which has the same effect as the original vectors acting together

Allotropes

Substances made of the same element but having different physical structures

Relative atomic mass

a number which indicates how many times the average mass of an atom of a certain element is heavier than 1/12 of the mass of a carbon-12 atom

Valence electrons

the electrons found in the outermost (highest) energy level and therefore the electrons with the highest energy

Potential difference

the work done per unit positive charge.

current

current is equal to the amount of charge that passes a point each second

Ohm’s law

current flowing through a conductor is directly proportional to the potential difference across the conductor provided the temperature remains constant.

EMF

the amount of energy provided per unit charge

charge

a property of a proton or an electron

Resistors in series

potential dividers

Resistance

a materials opposition to the flow of electric current

factors affecting resistance

nature of the material used, length of the wire, the thickness of the wire, temperature

formula for total resistance in parallel

1/Rt =1/R1+1/R2