The Structure of the Atom- Chapter 4 and 3.4 (page 75-77)

**The ______________ is defined as the smallest particle of an element that retains the properties of that element.**

History

400 BC Democritus:

1809 John Dalton

• Summarized results of his experiments and others to produce Dalton’s ___________________________.

Assumptions of the theory:

1	All matter is made up of _________________ particles called _____________.
2	Atoms of the ___________ element are identical in ______________. Atoms of _______________ elements are different in properties.
3	Atoms of different elements combine in ______________ number ratios to form _____________________.
4	Chemical _______________ involve the rearrangement, _________________ or separation of atoms to form new _____________________.

• 3 main laws that led to the discovery of the _____________

Important Laws

1. Law of definite proportions: A ___________________ contains the same ______________________ in the same proportion by _____________.

Example:

2. Law of Multiple Proportions: The same two _______________ can form different compounds.

Example:

3. Law of Conservation of Mass: Mass can neither be ______________ nor destroyed but ______________ in form.

Example:

Diagram of Dalton’s Atomic Model

What was wrong with Dalton’s Theory?

v

v

The Discovery of Subatomic Particles

1897 Thompson discovers the ______________ through the use of a ________________ ray tube. He knows it is ________________ charged and has an extremely _______________ mass.

1909 Millikan discovers the ____________ of an electron. It carries a charge of __________.

Plum Pudding Model (ball of positive charge with

negatively charged particles evenly distributed)

1910 Rutherford discovers the _____________ through the _____________________________ experiment which used ____________________. The proton is ______________ charged and has a much larger ____________.

Rutherford’s Atomic Model (sphere with dense

middle center called the _______________ with

______________ dispersed in an ______________.

1932 Chadwick discovers the ______________________ which has no ______________ and a mass similar to the _____________________.

Subatomic Particles and their Properties

Particle	Symbol	Location	Electrical Charge	Relative Mass in a.m.u*	Actual mass in grams
	e^-
	p^+
	n^0

*a.m.u : atomic mass unit

To make an atom’s extremely small mass easier to use, we compare the relative mass of an atom with the standard: _______________ which has a mass of exactly ____________ a.m.u

An atomic mass unit is then equal to 1/12 ^th the mass of ___________________.

What are the 2 regions of the atom as of now?

v Nucleus: dense center containing ___________________ and _____________________.

v Electron Cloud: region surrounding nucleus containing electrons and mostly ________________________.

Analogy:

Counting Subatomic Particles

v The number of protons and neutrons in a nucleus is called the ______________________.

Round atomic mass to ________________ number.

Nitrogen’s mass number is 14. ^__

v The number of protons in a nucleus is called the ______________________.

Nitrogen’s atomic number is 7!

------------ equals-------------------

number of neutrons

v A neutral atom has the ________________number of protons and electrons.

Examples

Element Symbol	Atomic Mass	Atomic Number	Mass Number	Protons	Electrons	Neutrons
H	1.008	1	1	1	1	0
Au
Be
Si
Br

How do Atoms Differ: Isotopes

v Isotopes are atoms that have the same number of ______________ but a different number of neutrons.

v Most elements contain a mixture of 2 or more ________________. Each one having its own

mass and abundance.

Isotope	Atomic number	Protons	Neutrons	Electrons	Mass (a.m.u)
Hydrogen-1
Hydrogen-2 (deuterium)
Hydrogen-3 (tritium)

v Represented by a ____________________.

v Can also use _____________________. Xtreme – 80

You Try ? ( Be Careful: Might not be most common isotope. Never use the given atomic mass on the periodic table unless absolutely necessary!!)

What the number of protons, neutrons and electrons in each atom?

19 57 204 46

F Fe Hg Ca

9 26 80 20

How to calculate Average Atomic Mass?

35 37

Cl 35.45 amu Cl

17 WHY? 17

v Average atomic mass is the weighted _____________________ of the masses of all naturally occurring _______________________.

Equation:

Average atomic mass = (% abundance of isotope x mass of 1^st isotope) + (% abundance of isotope x mass of 2^nd isotope) + ………

Example:

Element x has 2 natural isotopes. Calculate the average atomic mass. 1^st isotope has a mass of 10.012 a.m.u with 19.91% abundance. 80.09% of the 2^nd element has a mass of 11.009 a.m.u.

You Try!

_______________________________________________________________________________

Refer to “Isotopic Model” Activity

Ions

v An atom or group of atoms with a _______________________. The number of ________________________ does not equal the number of _____________________.

v WHY? Atoms ______________ or _______________ electrons to acquire stability like a noble gas.

Monatomic Ions (formed from a single atom) Cu⁺², F^-1

Cations Anions

________________ charge _______________ charge

________________ electrons _______________ electrons

The group number for metals(rep- ___________ the group number for

resentative) in columns 1A, 2A, and 3A nonmetals in columns 4A, 5A, 6A, and

is the ______________. 7A from 8 to get the charge.

Metals in group B(transition) must be

determined from a chart- See handout!

Ex. Sodium Na ^{+ ____} Ex. O ^{- ____}

Copper Cu^{+ ____ or} Cu^+____

Naming: Take the element name Naming: Drop the ending of the element name

and add the word and add ___________ plus ion.

___________

Try These: Write the formula for each ion and name it.

Calcium Aluminum Chromium Zinc

Chlorine Fluorine Sulfur Phosphorus

Refer to “ Journey into an Atom: Activity

Polyatomic Ions (formed from a group of atoms) NO₃^-1 , NH₄⁺¹

v See handout for ones you must know!

v You must memorize the chemical formula and the charge for all 13.

v There is only 1 cation : ammonium (NH₄⁺¹)

Tutorials:

Counting subatomic particles: http://science.widener.edu/svb/tutorial/protonscsn7.html

Atoms and Ions: http://lrc-srvr.mps.ohio-state.edu/shell-cgi/world/genquiz.pl

Ions: http://lrc-srvr.mps.ohio-state.edu/shell-cgi/world/genquiz.pl

Calculating Average atomic mass: http://lrc-srvr.mps.ohio-state.edu/shell-cgi/world/genquiz.pl