Science 10 Chemistry Mr McDonald

Matter

Elements We have the periodic table of the elements There is order to the table based on characteristics of the elements – What are some of these characteristics?

Atoms Recall Mass number – total number of protons and neutrons in the nucleus Atomic Number – number of protons Number of protons is constant but neutron and electron numbers can be different – Electrons: be in a full outer shell (if so called an ION) – Neutrons: be the same as protons but if not it’s an isotope

Electron shells For the first 20 elements the shells are: – 2, 8, 8, (2) These are the only electrons that you need to know. But after the 20 th element the shells can contain more electrons, based on orbitals.

Various models of the atom Dalton’s – “billiard ball” model Thomson – “raisin bun” model Rutherford – “Electron Cloud” model Bohr – best model to date

Bohr Makes an extension of the Rutherford model that the electrons are at certain energy levels from the nulceus

Bohr Diagrams Shows the total number of electrons surrounding the atom

Electron Dot Diagrams Used to describe the amount of valence (outer shell) electrons for each atom.

Review of terms Nucleus: The central part of an atom; contains the protons and neutrons. Electrons: small, negatively charged particles. Are found in electron shells OUTSIDE the nucleus. Electron Shells (orbital): 3D space where electrons are likely to be found. Valence electrons: Electrons found in outermost electron shell. It is these electrons that move from atom to atom. Octet Rule: All atoms strive for a FULLY FILLED outer (valence) electron shell. For most atoms (1 st row excluded—where 2 electrons is a “full” shell”), this is eight electrons. Atoms can gain or lose electrons to achieve an octet (8) of electrons.

Ions Ion: An atom that has either gained or lost an electron to achieve a stable octet of electrons. – Cation: an atom that has LOST electrons to form a positively charged ion. Example: Na  Na + + e - – Anion: an atom that has GAINED electrons to form a negatively charged ion. Example: F + e -  F -. All elements that form negatively charged ions have their name changed by adding “… ide” to the end. Thus, fluorine becomes a fluoride ion.

Compounds Binary compounds – Ionic compounds Compound between non-metal and metal Conducts electricity in aqueous solution – Molecular compounds Between non-metal and non-metal

Determining formula Need to determine the stable ion for each atom, we write the positive ion first and the negative ion last Take the charge of each element and “cross- over” to give how the elements combine If you have a factor of one another, can simplify Step 1:Si 4+ O 2- Step 2:Si 4+ O 2-  Si 2 O 4 Step 3:Si 2 O 4 SiO 2

Naming compounds Naming of compounds are different depending on the type of compound (ionic and molecular)

Naming compounds # of atoms Prefix # of atoms Prefix 1 mono 6 hexa 2 di 7 hepta 3 tri 8 octa 4 tetra 9 nona 5 penta 10 deca When there are more than one element need to describe this in the naming.

Rules for the Prefix System ONLY use the Prefix system for non-metal/non-metal compounds— NEVER for ionic compounds! (Exceptions: Classical (ous/ic) system: Used for metal ions with more than two possibilities; also used on occasion for metalloid compounds. If the first element named has only one atom, we do NOT use the Mono prefix—it is assumed the first element has one atom unless otherwise specified. Compounds where the first element named is hydrogen are acids— they use an entirely different naming system (see later PPT). Note that acids are always aqueous solutions; if the element is a gas, it is named using the prefix system. Example: HCl (g) is called hydrogen chloride; HCl (aq) is called hydrochloric acid. In some compounds, the vowel at the end of the prefix is dropped; this is done to make the name easier to say. Example: N 2 O dinitrogen monoxide (not monooxide). This is usually done when the second named element starts with a vowel (like oxygen).

Homework Pg38 # 9(NOT #b, #c do Cl), 13a,d,f, 15b,c,d, 18a,b,d,e,f Draw the ionic form of (charge): – N F Al Be Ca B

Some examples Name – SO 2 SO 3 OF 2 O 2 F 2 Write formula – Sulfur difluoride sulfur tetrafluoride – Sulfur hexafluoride disulfur difluoride

Naming for ionic compounds There is no use of prefixes. The formula is based on the electron transfer between the two elements – Which is based on the ions Remember that ionic compounds are more of a crystal lattice so the formula is just a formula unit

Some examples Name – LiCl KBr CaCl 2 MgO Write formula – Sodium fluoride barium bromide – Magnesium fluoride aluminium chloride

Using the Stock system Some elements can have more than one cation This is used to identify which cation to use For example copper(II) is Cu 2+ and copper(III) is Cu 3+

Polyatomic Ions Different atoms bonded by covalent bonds to give an ion. These are unit when placed in a compound they are treated as one unit When naming these compounds you would follow the same rules as ionic compounds.

Example Ammonium NH 4 + Sulfate SO 4 2- If these combine, the cross-over method would be used to give NH 4 + SO > (NH 4 ) 2 SO 4 Ammonium Sulfate

Hydrogen Compounds Compounds with Hydrogen are a little different They can be acids, or compounds with hydrogen and carbon. We will learn about simple acids in section 2.3 and the hydrogen and carbon compounds in later chemistry courses.

Seatwork/Homework Pg 55 all odd numbered letters and 6 Naming sheets for compounds