U1 Definitions

Electron Transition

The distance of travel when an electron emits radiation and falls down to a lower E level

Heterogeneous

Cannot be distributed evenly

Homogeneous

Uniform

Volatility

Tendency of a substance to vaporize

Isotopes

Atoms of the same atomic number but different mass number.

Radioisotopes

Isotopes with an unstable nuclei. Emits radiation as they change to become stable.

Relative Atomic Mass

The weighted average of all naturally occurring isotopes of an atom relative to 1/12 of the mass of one atom of carbon-12.

symobl: A_r

Relative Formula Mass

The sum of the relative atomic mass of all the atoms in a covalent molecule or formula unit of an ionic compound

symbol: M_r

Molar Mass

The mass in grams of one mole of a substance

unit: g mol^-1

The Mass Spectrometer

An analytical instrument used to measure the masses of the isotopes of an element and their abundances. It determines the composition of an unknown molecular substances.

Solid Sphere Model

John Dalton 1803

Plum Pudding Model

JJ Thompson 1904

Nuclear Model

Ernest Rutherford 1911 (Gold foil experiment )

Planetary Model

Niels Bohr 1913

Quantum Model (“Clouds of possibility”)

Erwin Schrodinger 1926

Orbitals

Volume of space where electrons have a high possibility of being found

Sublevels

Levels within energy levels becaus electrons need more space than just one line of the main level

s<p<d<f

Aufbau Principle

When adding electrons to an atom, the lower energy sublevels must be filled first in the order of overlapped sublevels

Hund’s Rule

Each orbital within a given sublevel must be filed with a single electrons before electrons are paired up. You may pair up electrons beginning from the left.

Pauli exclusion principle

Orbitals can only hold 2 electrons with opposite spin. The same direction of spin would repel the arrows and cause instability.

Mandeleev

Founded the current model of periodic table. Elements not yet found were positioned correctly on the pt because the chemical and physical properties of an element can show it’s relativity to other elements. The patterns on the pt can then be used to position those elements

isoelectric

Particles with the same number of electrons

First ionization energy

The energy required to remove one mole of electrons from one mole of atoms in the gaseous state.

Coulumb’s Law

2 factors that canc ahnge the force of attraction

1. charge magnitude: more charge, more force

2. distance between charges: more distance, less force

Effective Nuclear Charge

Net charge of force of attraction a valance electrons experiences with the shielding of inner electrons

ENC = # of p - # of inner e

ultraviolet

Lyman

Visible Light

Balmer

Infared

Paschen