Definitions Flashcards
What is the Principle of the Mass Spectrometer
To separate and deflect
Positively charged Ions
According to their atomic masses
When moving in a magnetic field
Energy Level
Orbital which electrons of equal energy can occupy
Visible Lines in Hydrogen Emission Spectrum
Balmer Series
Atomic Radius
Half the distance between the two nuclei of atoms of the same element in a single covalent bond
First Ionisation Energy
The minimum energy required
To completely remove
The most loosely bound electron
Of a neutral gaseous atom
In it’s ground state
Electronegativity
The relative force of attraction an atom has for the shared pair of electrons in a covalent bond
Isotopes Definition
Atoms of the same element which differ by atomic mass (number of neutrons in nucleus)
Radio Isotope Definition
Isotope atom with an unstable nucleus
Half-Life
Time taken for half of the sample to decay
What happens to an atom after alpha decay
Looses a ‘He’ atom
Radioactivity
Spontaneous decay of a nucleus, releasing radiation
Mole / Avogadro’s Constant
A mole of a substance is the amount of a substance that contains 6x10^23 particles of that substance
Chemical Equilibrium
A state of chemical balance where the rate of the forward reaction equals the rate of the reverse reaction
Dynamic Reaction
A reaction where the forward and backwards reactions are both occurring continuously
Le Chatelier’s Principle
If a reaction at equilibrium is put under stress, the equilibrium will shift to relieve the stress
Avogadro’s Law
Equal volumes of gases at the same temperature and pressure have equal number of moles
Charles’s Law
For a gas of a definite mass, at a constant pressure, the volume of the gas is directly proportional to the Kelvin temperature
Boyle’s Law
For a gas of a definite mass at a constant temperature, the volume of a given mass of any gas is inversely proportional to its pressure
Gay-Lussac’s Law of Combining Values
In a reaction between gases the volumes of the reacting gases and the volumes of any gaseous products are in the ratio of small whole numbers provided the volumes are measured at the same temperature and pressure
Kinetic Theory of (Ideal) Gases
- Volume is negligible compared to space it occupies
- No attractive or repulsive forces between particles
- Particles are in constant random motion and are constantly hitting walls of container and themselves
- Average kinetic energy of the particles is or optional to Kelvin temperature
- All collisions are perfectly elastic
Real Gas vs Ideal Gas
Molecules have volume, when gas it at high pressure / low volume it is not ok to say volume is negligible
Intermolecular forces are present
Collisions are not perfectly elastic
Ideal Gas
An ideal gas is one which obeys all the gas laws under all conditions of temperature and pressure
When do real gases behave most like ideal gases?
High Temperatures
Low Pressures / High Volumes
Arrhenius Acids / Bases
Dissociates in water to form H+ / OH-
What are Cathode Rays
Streams of negatively charged particles called electrons that travel in a straight line from the cathode to the anode
What is an energy level
The fixed energy value that an electron in an atom may have
What is an atoms ground state
The state in which the electrons occupy the lowest available energy levels
What is an atoms excited state
When the electrons occupy higher energy levels than those available in the ground state
Heisenburgs Uncertainty Principle
It is impossible to detect both the position and then velocity of an electron in an atomic orbital at any one time
What is a sub level
A subdivision of a main energy level and consists of one or more orbitals of the same energy
What is an element
A substance that cannot be split into simple substances by chemical means
Dobereiner’s Triads
A group of three elements with similar chemical properties in which the atomic weight of the middle element is approx. equal to the average of the other two
Newlands Octaves
Arrangements of elements in which the first and the eight element, counting from a particular element have similar properties
Mendeleev’s periodic law
When elements are arranged in order of increasing atomic weight the properties of the elements recur periodically
Atomic number of an element
The number of protons in the nucleus’s of an atom of the element
Modern Periodic Law
When elements are arranged in order of increasing atomic number, the properties of the elements recur periodically
Mass number
Sum of protons and neutrons
Isotopes
Atoms of the same element which have different mass numbers did to having different numbers of neutrons in their nuclei
Relative atomic mass
The average mass numbers of all the isotopes of an element when taking their abundances into account expressed on a scale where the isotope of a carbon-12 atom has an atomic mass of 12
What is a compound
A substance that is made up of two or more different elements combined together chemically
What is the Octet Rule
When bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost energy level
What is an Ion
A charged atom or group of atoms
Cations = positively charged
Anions = negatively charged
What is an ionic bond
The force of attraction between oppositely-charged ions in a compound. Ionic bonds are always formed by the complete transfer of electrons from one atom to another
What is a transition metal
A metal that forms at least one ion with a partially-filled d sublevel
What is a molecule
A group of atoms joined together. It is the smallest particle of an element or compound that can exist independently
What is the valency of an element
The number of atoms of hydrogen or any other monovalent element with which each atom of the element combines
What is a polar covalent bond
A bond in which there is unequal sharing of the pair or pairs of electrons
This causes one end of the bond to be slightly positive and the other end slightly negative
What is a Gas?
A gas is a substance which has no well-defined boundaries but diffuses rapidly to fill any container in which it is placed
Equation of State for an Ideal Gas
pV=nRT
R = universal gas constant = 8.31
