Chem Unit 2 Quiz 2

atomic #, atomic mass, mass # Isotopes, isotopic notation, ions atom models over years electron configuration, sub level, principle energy level, valence electrons

Atomic number

the number of protons and the nuclear charge of an atom, identifies the atom

Atomic mass

the weighted averaged of all the naturally occurring isotopes of an atom, always a decimal

Calculating Atomic Mass

atomic masses are weighted averages that take into account the natural abundances of each isotope

Mass number

the protons and neutrons in the nucleus. Equal to the number of nucleons. Identifies an isotope, always a whole number

Atomic mass unit (amu)

the unit of measure for a subatomic particles, 1/12th the mass of Carbon

Isotope

atoms of the same elements with a different number of neutrons. Mass number and number of nucleons will be different as well. Same atomic #, different mass # or same # of protons, different # of neutrons

Most common isotope

the isotope that exists in the greatest abundance. Round the atomic mass and you will get MCI

Isotopic notation

symbol of the element,the element’s atomic number and the mass number

Ion

a charged particle formed by the loss or gain of an atom’s electrons

Dalton Model (1803)

The atom is a solid indivisible sphere, also known as “Billiard Ball” model

Thompson Model (1897)

known as the Plum Pudding model, discovered the electron. The atom is a sphere with small electrons embedded in a positively charged mass

Experiment: Cathode Ray Tube

Rutherford Model (1911)

The atom is mostly empty space with a small dense nucleus with electrons moving around it like the planets move around the sun.

Experiment: Gold Foil

Bohr Model (1913)

The electrons in an atom move in circular fixed orbits at fixed distances from the nucleus. Problem is that this model only worked for explaining Hydrogen

Electron Cloud/ Wave Mechanical Model/ Modern Model (1926)

Introduces quantum mechanics to the world, describes electrons as both waves & particles

Orbitals

region of high probability of finding an electron

Electron Configuration Rules

Aufbau Principal: electrons occupy the orbitals of lowest energy first

Pauli Exclusion Principal: no two electrons can occupy the same space in an orbital

Hund’s Rule: each orbital can hold 2 electrons - fill each orbital /w 1 electron before pairing electrons in an orbital

Electron Configuration

electrons are distributed in the electron cloud into principal energy levels (1, 2, 3..), sublevels (s, p, d, f), orbitals (s has 1, p has 3, d has 5, f has 7) and spin (2 electrons allowed per orbital)

Valance Electrons

-the electrons in the outermost energy level

-the only electrons in a chemical reaction, # of electrons determine how atom will react

-Lewis/Electron dot diagrams show valance electrons only

Cation

an atom with 1, 2 , or 3 valence electrons will lose those electrons to become a stable ion, a positive ion is called a cation

Anion

an atom with 5, 6, or 7 valence electrons will gain electrons to become a stable ion, a negative ion is called an anion