CATALYST (10 minutes, individual work): Assignment #4 Valence Electrons LO: Describe patterns on periodic table. Predict valence electrons for a given element. EQ: How do you predict the number of valence electrons for a given element? LEVEL ZERO VOICE CATALYST (10 minutes, individual work): 1. Draw a B-2 ion. Label protons, neutrons, nucleus, electrons & electron cloud. Calculate the atomic number and atomic mass. 2. Draw 3 isotopes for Carbon Calculate the atomic number and atomic mass for each AGENDA Valence Exploration Class Discussion Review for test HOMEWORK 1. Finish processing tasks  

Every neutral atom has a unique number of electrons Balance out #protons to make it neutral charge   

Valence electrons – electrons in the outer shell of an atom, the atom wants 8 valence electrons   

Exception! H and He only need 2 valence Bond – when two/more atoms share valence electrons so they both have 8 valence electrons Exception! H and He only need 2 valence  

Elements are made of one type of atom He or H2 or O2 Sodium is an element because it only contains sodium atoms Gold is an element because it only contains gold atoms Oxygen gas (02) is also an element because it only has one type of atom

Bonded atoms form molecules molecule: a neutral particle that forms as a result of electron sharing EX: H2O: “H two O” or water EX: NaCl: “N A C L” or Sodium chloride or salt can be formed by two of the SAME atom Ex: O2: “O two” or oxygen gas H2: “H two” or hydrogen gas

Compound: a pure substance that contains molecules of the same type H20 (water), NaCl (salt), carbon dioxide (CO2) Different from an Element Gold, diamond, helium He or H2 or O2

Compounds have different properties than their individual components Chlorine gas + sodium metal = table salt (write down the discussion on the board)

Properties of Na (sodium) : Metal Grey color Soft (can cut it with butter knife) poisonous

Properties of Cl (chlorine) : Yellow Gas poisonous

But we know the properties of the compound are different from the properties of the parts of the compound so………….. Chlorine (not edible) + sodium (not edible) = SALT (delicious!!)

RECAP: Putting ATOMS together makes MOLECULES. If the atoms aren’t all the same in the molecule, it is a COMPOUND. Because a molecule can be an ELEMENT (O2)

Writing molecules:

Writing molecules: Coefficient: how many molecules there are Subscript: how many atoms there are in the molecule (small number)

Element: all atoms in molecule are the same element (H2, O2) Compound: different atoms in molecule (H2O, CO2) Mixture of elements: a mix of molecules that are elements Mixture of compounds: a mix of molecules that have different atoms Mixture of elements and compounds