Physical Science Review #2 Atom, Periodic Table, Lewis Dot Structures, Mole

Atom Basics Atom: smallest unit of matter – Composed of 3 subatomic particles In the nucleus – Protons (positive charge) – Neutrons (neutral charge) Outside Nucleus – Electrons (negatively charged) – Stays together because of the Positive and negative attraction between protons and electrons – Isotopes: atoms of the same element with difference masses because of different number of neutrons

Calculating Atom Stuff Atomic # = # Protons Atomic Mass = # Protons + # Neutrons # protons = Atomic # = # electrons if no charge # neutrons= Mass # - # protons # protons = Atomic # = # Electrons = Mass - #n # electrons = # protons

Bohr Models Inside nucleus you write # p & # n Outside you draw your electron orbitals. – 1 st level can only hold 2 electrons – 2 nd level can hold up to 8 # of valence electrons = # electrons in outside shell

Periodic Table Basics YOU MUST KNOW YOUR ELEMENTS! Rows = Periods Columns = Groups # of valence electrons = Group # Group 1 = Alkali Metals = Most reactive group Group 2 = Alkaline Earth Metals Middle = Transition Metals Group 7= Halogens Group 8 = Noble Gases = Least reactive group

Periodic Table Basics There are mostly metals on the periodic table (left side of metalloids) 6 metalloids (B, Si, Ge, As, Sb, Te) Non metals are on the Right side of metalloids Hydrogen is the only nonmetal on the left side of the periodic table

Lewis Dot Structures Show the # of valence electrons For single element, write element then dots around. (start with single dots at top, bottom, left, right, then double up your dots)

Lewis Dot Structures: Compounds When drawing Lewis Dot Structures for Compounds Use the NASL method. Remember all elements except H & He Need 8, H & He need 2 A is how many valence electrons are available S is how many are shared (N-A) this tells you how many electrons are in bonds (2 electrons per bond) L is # of lone dots

Lewis Dot: Charged Compounds On the A Step: – Add the number of charge if it is negatively charged – Subtract the number of charge if positively charged

Using the Mole Use train tracks to go from grams to mole or moles to grams. To figure out how many grams in 1 mole, use the periodic table mass Ex. Change 20 moles of carbon to g.

Other # of Atoms = How many of each type of element you have (In P 2 O 6 you have 8 total atoms) # of molecules how many of the compound you have: 8 H 2 O 2 = 4 atoms, 8 molecules)

Find the mass of Compounds Steps: 1.Write down the elements you have 2.Write down how many you have of each 3.Look up the mass of each element 4.Multiple your mass by how many you have 5.Add up all totals. Example: Find the mass of C 2 O 3