Ch. 2 – Basic Chemistry

I. Structure of the Atom Chemical Symbols Subatomic Particles

Chemical Symbols• Chemical Symbols are used to represent

element names• Capitals matter!• Element symbols contain ONE capital letter

followed by lowercase letter(s) if necessary.• Must be written correctly or will be wrong

on quiz/test

Co vs. COMetal that

forms bright blue solid

compounds.

Poisonous gas.

What elements must you know…• You must memorize elements 1-20 on the

periodic table• H = hydrogen• He = Helium• Li = Lithium• Be = Berrylium• B = Boron• C = carbon• N = nitrogen • O = oxygen• F = fluorine• Ne = Neon• Na = sodium

Continued• Mg = magnesium• Al = aluminum• Si = silicon• P = phoshorus• S = sulfur• Cl = chlorine• Ar = argon• K = potassium• Ca = calcium

What other elements must I know• You must also memorize the elements on the

memorization tips sheet you got• Quiz on _________ at the beginning of the hour• Ag = silver• Au = gold• Br = Bromine• Fe = iron• Hg = mercury• Ni = nickel• Pb = lead• Sn = Tin• Mn = manganese

Parts of an atom

• Atom = basic unit of matter• Every element is composed of one type of atom • Atoms are the smallest pieces of matter that

have properties of that element• Composed of protons, neutrons and electrons

– Protons (p+): charge of 1+– Neutrons (n0): no charge (neutral)– Electrons (e-): charge of 1-

Atomic Components

• Protons and Neutrons are located in the nucleus of the atom

• The nucleus is positively charged• It is surrounded by a cloud containing

electrons• Atoms of different elements differ in the

number of protons

Atomic Components

Subatomic Particles

POSIT IVECHARG E

PROT ONS

NEUT RALCHARG E

NEUT RONS

NUCLEUS

NEG AT IVE CHARG E

ELECT RONS

AT OM

Most of the atom’s mass. Atomic Numberequals the # of...

in a neutral atom

NUCLEUS ELECTRONS

PROTONS NEUTRONS NEGATIVE CHARGE

POSITIVE CHARGE

NEUTRAL CHARGE

ATOM

Subatomic Particles

• Quarks: very small particles that make up protons and neutrons

• Scientists have confirmed 6 different quarks• To study quarks scientists accelerate particles

and smash them into protons• The collision breaks apart the proton

Atomic Models

How small are atoms??• 24,400 atoms stacked on top of each other

= the thickness of a piece of foil• Scientists create scaled-up models to help

visualize atoms• Models are based on indirect evidence• There have been many different models

over the years

Electron Cloud Model• The model now used is the Electron Cloud Model• The electron cloud is the area where electrons

are MOST likely to be found• It is 100,000 times larger than the diameter of

the nucleus– Ex. Paperclip in a football stadium

Orbital

• Region where there is 90% probability of finding an electron.

Can’t pinpoint the location of an electron.

Density of dots represents degree of probability.• Which area is the

most dense?

Orbital

• Orbitals have different shapes.

Inside the Cloud

• Electrons are various distances away from the nucleus– Closer energy levels have less energy and can hold fewer

electrons• Ex. The closer you sit to the teacher in your class, the

less you can move around.• Each energy level (n) can hold 2n2 electrons.

Energy Level Max # of Electrons

1 2

2 8

3 8

4 18

Ch. 2 – Basic Chemistry continued…

II. Masses of Atoms Atomic Mass Mass Number

Isotopes

Atomic Mass

Particle Mass (g)

Electron 9.1093x10-28

Proton 1.6726x10-24

Neutron 1.6749x10-24

Which subatomic particle weighs the least?

Most of the mass is here!

• The atomic number of the element is the same as the number of protons the element has

• Elements are put in order of the atomic numbers on the periodic table

• The number is the same for every like atom – All Carbon atoms have 6 protons, so, the atomic number of carbon = ____

• How many protons does Oxygen have? ____

Atomic Number

68

• Sum of the protons and neutrons in the nucleus of an atom

Mass NumberAlso called atomic mass number

Always a whole number.

# of neutrons = mass # - atomic #

© Addison-Wesley Publishing Company, Inc.

• The number of electrons is equal to the number of protons in a neutral atom.

• The number of electrons can change, but it doesn’t change the properties of the atom

• If an atom loses or gains an electron, it is called an ion.

Number of Electrons

Summary equations# of protons = atomic number

# of neutrons = mass number – atomic number

# of electrons = atomic number, unless it’s an ion

Atomic mass = # of protons + # of neutrons

• Atoms of the same element with different numbers of neutrons.

Isotopes

C126

Mass #

Atomic #

Isotope symbol:

“Carbon-12”

• Draw Carbon -12, write down how many protons, electrons and neutrons are present. Also, label an electron, proton, neutron and nucleus.

Isotopes

•Protons = 6•Neutrons = 6•Electrons = 6

electrons

neutrons

nucleusprotons

Isotopes

© Addison-Wesley Publishing Company, Inc.

• Average Atomic Mass– reported on Periodic Table– weighted average of all isotopes

Isotopes

atoms of # total

atoms) of )(## (massatoms) of )(## (mass

Avg.AtomicMass

Avg.AtomicMass

• EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37.

Isotopes

atoms 10

atoms) (37)(2atoms) (35)(835.4 g

Metallic Character

• Metals• Nonmetals• Metalloids

1

2

3

4 5

6

7

Columns & Rows

• Group (Family) - Vertical• Period - Across1

2

3

4 5

6

7

Periodic Trends• Group # = # of valence e- (except He)

– Groups have similar reactivity. • Period # = # of energy levels

1A

2A 3A 4A 5A 6A 7A

8A

BOHR DIAGRAMS

• Picture representation of an atom• Shows information about the nucleus• Shows electron energy levels

How to draw Bohr Models• Draw small circle and inside circle, write

• Element symbol• # of protons• # of neutrons

• Look up what period the element is in (what row) and draw that many circles around your smaller circle

• Add electrons as small dots to each circle that is allowed, until you have the proper number of electrons

• Remember your number of electrons should equal the number of protons

Bohr model of Carbon-12

C p+=6N0=6

Term: Valence Electrons

• e- in the outermost energy level• Except for transition metals

• (The middle section of the table)

Lewis Dot Diagrams• Dots represent the valence e-

• (Electrons in outer level)• How many valence e- does sodium have?• One – So, Sodium has one dot

Ex. Sodium

Lewis Dot Diagram

• What group is Chlorine located?

• 17th• How many e- are in

Chlorines outer energy level? (Draw it to find out)

• 7 Ex. Chlorine

Lewis Dot Diagrams• Are useful to show how

chemical reactions occur• For example, sodium has 1

valence electron and chlorine has 7 valence electrons

• Sodium will give chlorine the extra electron, forming a chemical bond, and forming sodium chloride or tablesalt.

H2O2 hydrogen atoms

1 oxygen atom

Chemical Formula• Shows:

1) elements in the compound2) number of the atoms of each element in the

compound

Chemical Bond

• Strong attractive force between atoms or ions in a molecule or compound.– Ion – Charged particle

• Formed by:– transferring e- (losing or gaining)

– sharing e-

Stability

• Octet Rule– most atoms form bonds in order to have 8 valence

e-

– full outer energy level– like the Noble Gases! Ne

Stability is the driving force behind bond formation! (This makes the atoms happy!! )

StabilityWhich atoms are more likely to gain an electron? Which ones are more likely to lose an electron?

Gain or Lose???

Gain LoseNitrogen LithiumOxygen BerylliumFluorine BoronPhosphorus SodiumSulfur MagnesiumChlorine Aluminum

Stability

• Transferring e-

Sharing e-

Gain or Loss of e-

• Ion- charged particle that has lost or gained an electron

• Positively Charged (cations)- Lost electron (remember we like cats!)

• K+

• Negatively Charged (anions)- Gained electron• I -

Gain or lose of e-

• Think about it…..~ Each e- has a charge of -1,If you ADD one e- to an atom you have a charge of -1, 0 + -1 = -1~ What if you add 2 e-? -2~ What if you subtract a charge of -1?

0 – (-1) = +1 (Take away a neg charge)

Ionic Bond

• Attraction between 2 oppositely charged ions

• Transfer of electrons takes place• The compound now has a neutral charge• Sum ofcharges equal Zero

Ionic Bonds

• Bond usually forms between metals and non-metals– ***Usually the elements are across the table from

each other***

Covalent Bond

• Some atoms are unlikely to lose or gain electrons• Instead they share e- between two nonmetals• Creates a molecule• Only form between Nonmetallic elements**usually two elementsFrom the right side of The table bonded together**