Chem Unit 2 & 3 test

number of protons in the nucleus of an atom, identifies the element

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

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

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

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

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

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

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

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

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

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

region of high probability of finding an electron

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

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)

-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

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

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

Vertical columns on the PT where all the elements have the same # of valance electrons, have similar properties and the size of atoms increase as you go down a group

Horizontal rows on the PT where elements have the same # of energy levels

size of atoms decrease as you move across period

the ability to attract electrons in a chemical bond

energy required to remove a valance electron from an atom

Size of an atom, measured by the distance between two nuclei of the same atom

Atomic radius increases as you go down a group because there are an increasing number of principal energy levels

elements to the left of the staircase, except hydrogen. Properties of metals include luster, conductivity, malleability, ductility, and losing electrons easily

elements to the right of the staircase, plus hydrogen. Non-metals are dull, brittle, nonconductors ans gain electrons easily

6 elements that border the staircase, they have metallic and nonmetallic properties simultaneously. Often uses in technology because they are semiconductors

these elements in groups 3-12 are brightly colored solutions and have multiple positive oxidation numbers, less reactive than groups 1 and 2

most reactive metals on the PT, contain one valance electron and can not be found in nature b/c of their reactivity

metals in group 2 that contain 2 valance electrons. Can not be found in nature but are less reactive than alkali metals

nonmetal elements in group 17 and each element contain 7 valance electrons. This is the only group containing elements that exist in all 3 phases (F2 and Cl2 are gases, Br2 is a liquid, I2 is a solid

nonmetal elements in group 18, each has a full set of valance electrons and are nonreactive

ability to be pounded into sheets

ability to be pulled into a wire

a substance that allows for the flow of heat and electricity

a substance that does not allow for the flow of heat and electricity