ATOM – smallest piece of an element

Nucleus› Very dense, almost all the mass of the atom,

but very small› Protons – positively charged, one AMU› Neutrons – no charge (neutral), one AMU

Energy levels› Electrons – e- -negatively charged, very small› First energy level – only two electrons› Later energy levels – eight electrons

Element Name

Hydrogen Helium Lithium sodium

# protons 1 2 3 11

# electrons 1 2 3 11

# neutrons 0 2 3 11

Atomic Number 1 2 3 11

Atomic Mass Number

1 4 6 22

ATOMS – smallest piece of an element› GROUND STATE – overall zero charge› Equal numbers of protons and electrons

IONS – atoms with charges!› Electrons have been stolen… the

imbalance of protons (positive) and electrons (negative) results in a charged particle

Chlorine has 17 protons and 17 electrons The chloride ion stole an electron from another

atom… it now has 17 protons and 18 electrons It has a negative charge because it has more

electrons than protons

# protons

# electrons

Charge(protons – electrons)

Cation, anion or neutral atom?

Symbol

Name

4 4 0 Neutral Be Beryllium

4 2 2+ Cation Be2+ Beryllium

17 17 0 Neutral Cl Chlorine

17 18 1- Anion Cl- Chloride

7 7 0 Neutral N Nitrogen

7 10 3- Anion N3- Nitride

How can we determine what charge an ion will have?

The OCTET rule… atoms want to be like noble gases and have eight electrons in their valence (outer) energy level

We can predict charges with groups of the periodic table

Groups of atoms that share electrons with each other, but then steal more!› Or electrons they were sharing were stolen

from them…› Names do NOT end in -ide

Ions with opposite charges are attracted to each other like magnets› We call this attraction an ionic bond› Compounds formed by ionic bonds are called

ionic compounds

Charges are shown with little numbers up = superscript… K1+

Numbers of ions in the formula are shown with little numbers down = subscript… O2

We balance the charges of the ions› Potassium fluoride

K1+ + F1- -> KF

› Lithium oxide Li1+ + O2- -> Li2O

› Magnesium bromide Mg2+ + Br1- -> MgBr2

IONIC Compounds MOLECULAR Compounds

Steal electrons = ionic bond Share electrons = covalent bond

Ions and polyatomic ions Atoms

Metal + Non-metal Non-metal + Non-metal

Formula unit – balanced charges Molecule – numbers of atoms

Second element ends in –ide Second element ends in –ide

NO prefixes YES prefixes

Na2O – sodium oxideMgCl2 – magnesium chlorideKOH – potassium hydroxide

CO – carbon monoxideN2O – dinitrogen oxide

Si3N4 – trisilicon tetranitride

Naming acids is similar to naming ionic compounds… › Cl- is chloride

HCl is hydrochloric acid

› SO42- is sulfate

H2SO4 is sulfuric acid

Not this mole…

This mole…

6.02 x 1023

Amedeo Avogadro, 1811 - proposed that the volume of a gas at a given pressure and temperature is proportional to the number of molecules or atoms of the gas, no matter how large or small each atom or molecule is

› In other words, more molecules = more

volume

Many scientists… Jean Perrin, JJ Loschmidt, Robert Millikan, Michael Faraday… over many years were involved in experiments that led to the determination of the number of molecules

In 1906, Jean Perrin proposed naming the number in honor of Avogadro… › Avogadro’s number = 6.02 x 1023

One mole of a substance has a gram mass equal to the atomic mass (AMU)of that substance› Carbon-12 has a mass of 12 AMU

One mole of Carbon-12 has a mass of 12 g

› One molecule of H2O has a mass of 18 AMU One mole of H2O has a mass of 18 g So if you have 18 g water, you have…

6.02 x 1023 molecules of water

Substance

Atomic mass (AMU)

Molar Mass (kg)

Total mass

# moles # molecules

Helium 4.0 AMU 4.0 g 4.0 g 1 mol 6.02 x 1023

Helium 4.0 AMU 4.0 g 8.0 g 2 mol12.04 x 1023 =

1.20 x 1024

Helium 4.0 AMU 4.0 g 2.0 g ½ mol 3.01 x 1023

CO2

C = 12.0 AMU O = 16.0 AMU

+O = 16.0 AMU

44.0 AMU

44.0 g 44.0 g 1 mol 6.02 x 1023

CO2 44.0 AMU 44.0 g 11.0 g ¼ mol 1.51 x 1023

NaCl

Na = 23.0 AMU+ Cl =35.5 AMU 58.5 AMU

58.5 g 175.5 g 3 mol18.06 x 1023 =

1.81 x 1024

Switching between units› Atomic mass <-> molar mass <-> moles› Kilometers <-> Meters <-> Centimeters

Unit conversion factors100 m = __?__ cm

100 m x 100 cm = 10,000 cm 1 m

1 hour = ______ seconds1 hr x 60 min x 60 sec = 3600 seconds

1 hr 1 min

1 year = ______ seconds1 yr x 365 days x 24 hr x 60 min x 60 sec = 31,536,000

seconds 1 yr 1 day 1 hr 1 min

60 miles/hr = ________ feet/second60 mi x 5280 ft x 1 hr x 1 min = 88 feet/sec

1 hr 1 mi 60 min 60 sec