Atom StructureAtom Structure

Chapter 3Chapter 3

I. DefintionI. Defintion

Atoms are the Atoms are the fundamental unit fundamental unit of which elements of which elements are composed. are composed.

II. StructureII. Structure

What makes up What makes up an atom?an atom?–3 Subatomic 3 Subatomic particlesparticles

SubatomiSubatomicc

ParticleParticle

FoundFound ChargeCharge Mass Mass (amu)(amu)

III. Atomic MassIII. Atomic Mass

Where is the mass Where is the mass of the atom found?of the atom found?–NucleusNucleus

p + n = amup + n = amu

IV. Periodic tableIV. Periodic table

V. PracticeV. PracticeLi Li NeNeClCl

How many protons, How many protons, neutrons, and neutrons, and electrons?electrons?

VI. Atomic NotationVI. Atomic Notation

Lets try!Lets try!

VII. IsotopesVII. Isotopes

Why is the AMU not a whole Why is the AMU not a whole number?number?– ATOMIC MASS IS AN AVERAGE MASS ATOMIC MASS IS AN AVERAGE MASS

OF ALL ATOMS OF AN ELEMENTOF ALL ATOMS OF AN ELEMENT

ISOTOPE – Different numbers of ISOTOPE – Different numbers of neutrons in nucleus.neutrons in nucleus.

IsotopesIsotopes

Protons job- giving the element Protons job- giving the element it’s identityit’s identity

Neutron’s job - give the element Neutron’s job - give the element more massmore mass

Isotopes- same element (same # Isotopes- same element (same # of protons), but different masses of protons), but different masses (so the # of neutrons can (so the # of neutrons can change!)change!)

Isotopic NotationIsotopic Notation

This would be Carbon-This would be Carbon-1414

(the name of the element (dash) (the name of the element (dash) the mass of the element)the mass of the element)

This is Carbon-12 This is Carbon-12

ExampleExample:: Chlorine has a mass on the periodic table of 35.453 amu. Chlorine has a mass on the periodic table of 35.453 amu.

There are 2 isotopes of chlorine. There are 2 isotopes of chlorine.

7755%% cchhlloorriinnee--3355

2255%% cchhlloorriinnee--3377..

ISOTOPES CONT….

Sample ProblemSample Problem Chlorine-35 has an atomic mass of Chlorine-35 has an atomic mass of

34.969 amu and has an abundance 34.969 amu and has an abundance of 75.770%. Chlorine-37 has an of 75.770%. Chlorine-37 has an atomic mass of 36.966 amu and has atomic mass of 36.966 amu and has an abundance of 24.230%. Calculate an abundance of 24.230%. Calculate the average atomic mass of the average atomic mass of chlorine.chlorine.

Step 1: Multiply the mass of each isotope by its percent abundance

Step 2: Sum the results

You TryYou Try Calculate the average atomic mass Calculate the average atomic mass

for element X. Can you figure out for element X. Can you figure out what X is? It is Used to treat what X is? It is Used to treat mental disorders.mental disorders.

ISOTOPEISOTOPE MASS MASS (AMU)(AMU)

AbundancAbundancee

%%66XX 6.0156.015 7.5%7.5%

77XX 7.0167.016 92.5%92.5%

VIII. IONSVIII. IONS A neutral atoms have A neutral atoms have

same # of protons same # of protons and electrons.and electrons.

Atoms can gain or Atoms can gain or lose electron(s) lose electron(s) becoming a charged becoming a charged ionion

ExampleExample: Na has 11 : Na has 11 protons and 11 protons and 11 electronselectrons

IONSIONS

• Na can lose 1 electron making it have a charge of +1

Na1+ or Na+

IONSIONS

Some Some elements can elements can become become negative ions negative ions by GAINING by GAINING electrons.electrons.

IONSIONS

Will gain 1 Will gain 1 electron electron therefore an therefore an overall (1-) overall (1-) charge.charge.

99+++ 10+ 10--= 1= 1--

FF--

Ions Charges & The Ions Charges & The Periodic TablePeriodic Table

Label these on your periodic tables

Atoms want to be like the noble gases (group 8) because noble gases are very stable (unreactive/inert)… Other atoms will lose/gain electrons to become like one.

IX. Bohr Diagrams IX. Bohr Diagrams Sec 11-2 (p. 366) Sec 11-2 (p. 366)

Wave Mechanical ModelWave Mechanical Model

A. Electron Energy LevelsA. Electron Energy Levels•Energy levels begin closest to nucleus & move further out

1st energy level = max. of 2 e-

2nd energy level = max. of 8 e-

3rd energy level = max. of 8 e-

•An energy level must be full before electrons move to the next level. •An element is more stable when energy levels are full

Practice- Lets draw them!

1.Lithium

1.Magnesium