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Chapter 2 part 1

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Law of conservation of mass

Dalton

Mass is neither created or destroyed in chemical rxns.

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Law of definite proportions

Dalton In a given compound the relative

number and kind of atoms is constant.

Example: Water = 2 H and 1 O

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Dalton’s Atomic Theory

1. each element is composed of atoms

2. All atoms of a given element are identical

3. A chemical compound is the result of the combination of atoms of 2+ different elements

4. Atoms of an element are not changed into different types of atoms by chemical rxns

(MOVIE)

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Millikan

Discovered the charge and mass of an electron

1.6 X 10 -19 C (coulomb)

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Radioactivity

Three types of radiation Alpha α +2 charge Gamma γ no charge Beta β -1 charge

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Rutherford

Most of the mass of an atom and all of its positive charge resides in a very small dense region (nucleus)

Most of the volume of the atom is empty space around the nucleus

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Atomic Structure Proton

Symbol p+

Charge = 1.602 x 10-19 C (coulomb)Mass = 1.0073 amu

Electron Symbol = e-

Charge = -1.602 x 10-19 CMass = 5.486 x 10-4 amu

NeutronSymbol = n0

no charge Mass = 1.0087 amu

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Units = amu or g/mol

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A

ZX

A = Atomic mass ( p+ n)

Z = Atomic number ( p)

X = element Symbol

Complete Chemical Symbol

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QuestionHow many neutrons, protons and electrons are in carbon?

C 12

6

C = Carbon

12 = Atomic Mass ( protons + neutrons)

6 = atomic Number (protons)

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Answer

12 = p + n

6 = protons

12 – 6 = 6 neutrons

In an atom with out a charge the number of protons is equal to the number of neutrons

Thus: 6 electrons

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Question

Write the complete chemical symbol for the following elements.

Magnesium Sodium Tungsten

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Determining Sub Atomic Particles

12

6

C = Carbon

12 = Atomic Mass/weight ( protons + neutrons)

6 = atomic Number (protons)

C

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Isotopes

Isotopes Atoms of a given element that differ in number of

neutrons and thus in mass.

Isotope Protons Electrons Neutrons

11C 6 6 5

12C 6 6 6

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Isotopes Cont.

When writing isotopes the atomic number ( # of p+) stays the same, but the Atomic Mass (p+ + n0) changes due to the addition and subtraction of neutrons.

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Formulas

Chemical Indicates actual numbers and type of atoms in a molecule H2O2 C2H4

Empirical gives only relative number of atoms of each type HO CH2

Structural individual bonds are shown, indicated by lines

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average atomic mass Amu = Average Atomic Mass Unit The average atomic mass (weight) of an

element is equal to the sum of the products of each isotope’s mass (in amu) multiplied by it’s relative abundance.

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EXAMPLE OF AVERAGE ATOMIC MASS PROBLEM Naturally occurring chlorine is 75.53% Cl-

35 which has an atomic mass of 34.969 amu, and 24.47% Cl-37, which has an atomic mass of 36.966 amu.

Calculate the average atomic mass of chlorine.

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EXAMPLE OF AVERAGE ATOMIC MASS PROBLEM (CONT) Average atomic Mass = [ (%/100) (Atomic Mass) ] Average atomic mass = (0.7553) (34.969 amu) +

(0.2447) (36.966 amu) = 26.41 amu + 9.045 amu = 35.46 amu

NOTE: The average atomic mass of an element is closest in value to the atomic mass of the most abundant isotope.

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Alkali metals

Alkaline Earth Metal

Halogens

Metals Non Metals

Metalloids

TRANSITION METALS

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DIATOMIC SEVEN

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Nomenclature

Chapter 2 part 2Check out these videos for more help or if you are absent Naming molecular compounds Writing formulas for molecular compounds Naming ionic compounds video Writing formulas for Ionic compounds

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2.7 Ions and ionic compounds

When negative electrons are removed or added to an atom the charge of that atom changes from its neutral state to a charged state ( + or - )

Ion: charged particle

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a cation is a particle that carries a positive electrical charge. The cation gets this positive charge from losing negatively

charged electrons.

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Anions are ions that carry a negative electrical charge. Anions get their negative charge by gaining one or more electrons

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Trick

Na+Cl-

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Example

Na = atomic number 11 atomic mass = 23

11 protons, 12 neutrons, 11 electrons

Na- = 11 protons, 12 neutrons, 12 electrons

We added an additional negative charge (e-) creating a negatively charged particle.

11 + -12 = -1 charge on Na

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Reverse example

Na = atomic number 11 atomic mass = 23

11 protons, 12 neutrons, 11 electrons

Na+ = 11 protons, 12 neutrons, 10 electrons

We subtracted a negative charge (e-) creating a positively charged particle.

11 + -10 = +1 charge on Na

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Question

How many protons and electrons does Se2- ion posses?

How many protons and electrons does Cr3+ ion posses?

What kind of ions are these molecules and why?

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Answer

Se2- : anion 34 protons (atomic number) 36 electrons = -34 + -2 = -36

Cr3+ : Cation

24 protons (atomic number) 21 electrons = 24 – 3 = 21

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Nomenclature (Naming)

As of 2007 there are 31,000,000 known compounds.

Your are options are

A: memorize all 31,000,000 names

B: Learn how to name them memorize about 50 things that will allow you to name all 31,000,000.

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Polyatomic Ions

Atoms joined as a molecule, but they have a net positive or negative charge.

Example:

NO3-, SO4

2-

I will give you a list. You need to try to memorize them all… yes all.

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Polyatomic Ion Rap

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Cation and Anions to Memorize

Write these on your binder periodic table

+/-3 +/-4

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Putting the pieces together

Na+ Cl- Mg2+ 2Cl-

NaCl is an ionic compound

MgCl2 is an ionic compound

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Ionic Compounds

Contain both positively and negatively charged ions.

In general ionic compounds are made of metals and nonmetals.

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Covalent compounds

2 negatively charged elements

2 non metals

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Question

Write the ionic compound for:

Magnesium and Nitrogen

Magnesium and NO3-

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Answer

Mg3N2

Mg(NO3)2

Count the total number of each type of atom in the molecules above.

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Homework

Pg 71

#’s 37,40,45,47,48

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2.8 Naming ionic compounds

PINK SHEET

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