Chemistry is the study of… MATTER!!!!! Matter is any substance which: Occupies space (i.e. has volume) Has mass Found in 3 phases: liquid, solid, gas, (aqueous, dissolved in water) Can’t be created or destroyed, it only changes form

What makes up an atom? Atoms are made of three types of subatomic particle Protons (p+) - a positively charged particle located in the nucleus Neutron (n0) - a neutral (uncharged) particle located in the nucleus Electron (e-) - a negatively charged particle located outside the nucleus

Atomic Number = number of protons (p+) Atomic Mass = total of protons (p+ ) and neutrons (n0)

Ion Formation When an atom gains or loses electrons they become electrically charged particles called Ions Metals tend to lose electrons Positive ions are called CATIONS Non-metals tend to gain electrons Negative ions are called Anions

How many oxygen ions, O2- are present in each formula: Counting Atoms How many oxygen ions, O2- are present in each formula: MgO C6H12O6 2 SO2 Mg(OH)2 3Sn(Cr2O7)2 1 6 4 2 42

Bohr diagrams show how many electrons appear in each electron shell around an atom. The first electron shell holds 2 electrons The second electron shell holds 8 electrons (Stable Octet) The third electron shell holds 8 electrons The fourth electron shell holds 18 electrons The period number = the number of shells in the atom. Lewis diagrams show only an atom’s valence electrons and the chemical symbol The column number = the number of valence electrons (electrons in the outer shells in the atom).

Forming Compounds When two atoms get close together, their unpaired valence electrons interact. Each atom in the compound attempts to have a ‘full’ outer shell of valence electrons. Unpaired electrons are involved in the bonding and the lone pair electrons are not.

Ionic Compounds positive and negative ions. Metal + Non-Metal Electrons are given and taken.

Covalent Compounds negative ions. Non-metal + Non-metal Share electrons

Ionic vs. Covalent Ionic: Metal + Non-metal Ex: Sodium Chloride NaCl Covalent Non-metal + Non-metal Ex: trinitrogen dioxide N3O2

Naming Simple Ionic Compounds identify the two elements aways write the metallic element first. change the ending of the 2nd element (non-metal) to “ide” Magnesium bromide MgBr2 = K2O = CaCl2 = Potassium oxide Calcium chloride

Understanding the Formula Simple Ionic Compounds Since the OVERALL charge on a COMPOUND (MgO, MgCl2) is ZERO, the positive charges must balance the negative charges. Therefore, if a metal ion (Mg2+) has a charge of +2, then it can form a compound with either: ONE non-metal ion (O2-) with an ion charge of -2. MgO Math: 1(+2) + 1(-2) = 0 TWO non-metal ions (Cl1-) with an ion charge of -1. MgCl2 Math: 1(+2) + 2(-1) = 0

Learning Check A. Sodium and Sulfur Na+, S2- Na2S Write the correct formula for the compounds containing the following elements: A. Sodium and Sulfur Na+, S2- Na2S B. Aluminum & Phosphorus Al3+, P3- AlP C. Magnesium & Nitrogen Mg2+, N3- Mg3N2

Names & Formulas for Multivalent Ionic Compounds It is easy to write the formulas for multivalent ionic compounds, because they tell you their combining capacities. Example 1) Gold (I) chloride Au+1 Cl-1 AuCl PbO2 2) Lead (IV) oxide Pb+4O-2

Naming for multi-valent compounds

Learning Check CuO (Cu2+ ) copper (II) Oxide FeCl3 (Fe3+) iron (III) chloride CuO (Cu2+ ) copper (II) Oxide SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Au2O3 (Au3+) Gold (III) Oxide

Ca1 (OH)2 Ca(OH)2 Na2 (CO3) Na2CO3 Polyatomic ions have their own combining capacity that should be used when writing chemical formulas. Example: Compound formed with Calcium (Ca2+) and Hydroxide (OH-) would be… Example: Compound formed between Sodium (Na+) and Carbonate (CO32-) would be… Ca1 (OH)2 Ca(OH)2 USE BRACKETS AROUND THE POLYATOMIC IONS!! Na2 (CO3) Na2CO3

Naming compounds containing polyatomic ions Hint: if the fomurla contains more than two elements than it’s a good chance it contains a polyatomic ion, so go to your polyatomic ion chat. To name these follow the sames rules except for polyatomic ions do not change their names. e.g. Na3PO4 Sodium Phosphate

Covalent Compound Names & Formulas Prefixes are used before the atom name to indicate the number of atoms in the molecule. Example: N3O2 = trinitrogen dioxide CO = carbon monoxide trisilicon hexaphosphide Si3P6 Covalent molecules have subscripts that show the actual number of atoms in the molecule, so DO NOT DIVIDE BY COMMON DENOMINATOR!!