Subatomic particles Electron Proto n Neutro n Nam e SymbolCharge Relative mass Actual mass (g) e-e- p+p+ n0n0 +1 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10.

Subatomic particles

ElectronProtonNeutron

Name

Symbol

Charge

Relative mass

Actual mass (g)

e-

p+n0

-1+10

1/1840

1

1

9.11 x 10-

28

1.67 x 10-

241.67 x 10-

24

Counting the Pieces Atomic Number = number of

protons in the nucleus # of protons determines kind of

atom (since all protons are alike!)

the same as the number of electrons in the neutral atom.

Mass Number = the number of protons + neutrons.

These account for most of mass

Counting the Pieces

Protons: equal to atomic number

Neutrons: Mass Number – Atomic Number

Electrons: In a neutral atom equal to atomic number

Symbols

Contain the symbol of the element, the mass number and the atomic number.

Symbols Contain the symbol of the

element, the mass number and the atomic number.

X Massnumber

Atomicnumber

Symbols Find the

number of protons

number of neutrons

number of electrons

Atomic number Mass Number

F19 9

SymbolsSymbols Find the Find the

–number of protonsnumber of protons

–number of neutronsnumber of neutrons

–number of electronsnumber of electrons

–Atomic numberAtomic number

–Mass NumberMass Number

Br80 35

SymbolsSymbols if an element has an atomic if an element has an atomic

number of 34 and a mass number number of 34 and a mass number of 78 what is the of 78 what is the

–number of protonsnumber of protons

–number of neutronsnumber of neutrons

–number of electronsnumber of electrons

–Complete symbolComplete symbol

SymbolsSymbols if an element has 91 protons and if an element has 91 protons and

140 neutrons what is the 140 neutrons what is the

–Atomic numberAtomic number

–Mass numberMass number

–number of electronsnumber of electrons

–Complete symbolComplete symbol

SymbolsSymbols if an element has 78 electrons and if an element has 78 electrons and

117 neutrons what is the 117 neutrons what is the

–Atomic numberAtomic number

–Mass numberMass number

–Number of protonsNumber of protons

–Complete symbolComplete symbol

What if Atoms Aren’t Neutral Ions: charged atoms resulting

from the loss or gain of electrons

What if Atoms Aren’t Neutral Anion: negatively charged ion;

result from gaining electrons Take the number of electrons in a

neutral atom and add the absolute value of the charge

81

35

Br1- Identify:

Number of ProtonsNumber of NeutronsNumber of Electrons

What if Atoms Aren’t Neutral Cation: positively charged ion;

result from the loss of electrons Take the number of electrons in a

neutral atom and subtract the value of the charge

27

13 Al 3+

Identify:Number of ProtonsNumber of NeutronsNumber of Electrons

Isotopes

Atoms of the same element can have different numbers of neutrons

Different mass numbers Called isotopes

Naming Isotopes

We can also put the mass number after the name of the element.

carbon- 12 carbon -14 uranium-235

Atomic Mass How heavy is an atom of oxygen?

There are different kinds of oxygen atoms

We are more concerned with average atomic mass

Average atomic mass is based on abundance of each element in nature.

We don’t use grams because the numbers would be too small

Measuring Atomic Mass

Unit is the Atomic Mass Unit (amu)

It is one twelfth the mass of a carbon-12 atom

Each isotope has its own atomic mass, thus we determine the average from percent abundance

C lass ifica tion o f M a tte r

E lem ents C om pounds

Pure Substances

H om ogeneous(SO LU TIO N S)

C o llo ids S uspens ions

H eterogeneous

Mixtures

Matter

Pure Substances Cannot be physically

separated Every sample has the same

characteristics and they can be used to identify a substance

Elements Are made up of ONE type of atom

Atoms are the smallest unit of an element that maintains the chemical identity of that element

They can be found on the Periodic Table

Examples: Carbon, Nitrogen, Calcium

Compounds

Can be broken down into simple stable substances

Are made up of two or more types of atoms that are chemically bonded

Examples: Water (H2O), sugar (C12H22O11)

Mixtures

A blend of two or more kinds of matter, each which retains its own identity and properties

Homogeneous Mixtures Have uniform

composition Also known as

SOLUTIONS

Examples: salt water, tea

Solutions ALLOYS are solid solutions that

contain at least 1 metal They are blended together so that

they have more desirable properties Some alloys you may know are:

Stainless Steel: iron, chromium, and zinc Brass: zinc and copper Bronze: tin and copper Sterling Silver: copper and silver

Heterogeneous Mixtures

Do not have uniform composition You can see the particles in them

Examples: Sand on the beach (contains sand,

shells, rocks, bugs, etc) Soil (contains dirt, rocks, worms, etc) Chicken Soup (contains water, chicken,

veggies etc)

Suspensions A heterogeneous mixture where the

solid particles eventually settle out of solution

Examples: Muddy water Mixtures of two solids Paint

Properties of Matter

All pure substances have characteristic properties

Properties are used to distinguish between substances

Properties are also used to separate substances

Physical Properties

A Physical Property is a characteristic that can be observed or measured without changing the composition of the substance

Physical properties describe the substance itself

Examples Physical State Color Mass, shape, length Magnetic properties

Chemical Properties A Chemical Property

indicates how a substance will react with another

Chemical properties cannot be determined without changing the identity of the substance

Examples: Iron Rusting Silver Tarnishing

Physical Changes

A Physical Change is a change in a substance that does not alter the substance’s identity Examples:

Grinding Cutting Melting Boiling

Chemical Changes A change in which one or more

substances are converted into different substances is called a Chemical Change

Signs of a Chemical Change: Color Change Gas is Released Temperature Change Precipitate – Solid falls out of solution Substance Disappears

How Atoms Combine

Two or more atoms that are chemically combined make up a compound

The combination results in a chemical bond, a force which holds elements together in a compound

Covalent Bonds

Covalent Bonds are formed when atoms in a compound share electrons

Molecule – two or more atoms held together by a covalent bond

Usually occurs between nonmetals

Covalent Bonding in Water

Ions

An atom that has gained or lost an electron is called an ion.

Multiple atoms can combine to form an ion – called a Polyatomic Ion

Silicate (SiO44-) and Carbonate (CO3

2-) are important in forming materials at Earth’s Surface

Ionic Bonding

Positive and negative ions attract each other

Ionic Bonds occur when oppositely charged ions form a compound

Usually consist of 1 metal and 1 nonmetal

Positive ion written first in chemical formula (NaCl)

Ionic compounds have a neutral charge

Ionic Bonding in NaCl

Metallic Bonds

Metals share valence electrons between all atoms

Like a group of positive ions in a sea of electrons

Atomic Theory and Structure

Democritus

Democritus added: Matter is composed of atoms

which move through empty space Atoms are solid, homogeneous,

indestructible, and indivisible Different atoms have different

shapes and sizes The size, shape, and movement

of atoms determine their properties

Leading to the modern theory Late 1700’s - John Dalton- England. Teacher- summarized results of his

experiments and those of others. Dalton’s Atomic Theory Combined ideas of elements with

that of atoms. Saw atoms as small solid spheres.

Billiard Ball Model.

Dalton’s Atomic Theory All matter is made of tiny indivisible

particles called atoms. Atoms of the same element are

identical, those of atoms of different elements are different.

Atoms of different elements combine in whole number ratios to form compounds.

Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

Law of Conservation of Mass The law of conservation of mass

states that matter is neither created nor destroyed in chemical reactions

Discovery of the Electron J. J. Thomson - English

physicist. 1897 Made a piece of equipment

called a cathode ray tube. It is a vacuum tube - all the air

has been pumped out.

Thomson’s Experiment

Voltage source

+-

Vacuum tube

Metal Disks

Thomson’s Experiment

Voltage source

+-

Thomson’s Experiment

Voltage source

+-

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Voltage source

Thomson’s Experiment

By adding an electric field

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric fieldBy adding an electric field

+

-

Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field he By adding an electric field he found that the moving pieces found that the moving pieces were negativewere negative

+

-

Plum Pudding Model

Proposed by JJ Thomson

Said the atom had a uniform positive charge in which the negatively charged electrons resided

Lead block

Uranium

Gold Foil

Fluorescent Screen

He Expected

The alpha particles to pass through without changing direction very much.

Because…? …the positive charges were

thought to be spread out evenly. Alone they were not enough to stop the alpha particles.

What he expected

Because

He thought the mass was evenly distributed in the atom

Since he thought the mass was evenly distributed in the atom

What he got

How he explained it

+

Atom is mostly empty. Small dense,

positive piece at center. Alpha particles

are deflected by it if they get close enough.

+

The Bohr Ring Atom

n = 3n = 4

n = 2n = 1

Electron Cloud Theory

What are acids and bases?

ACIDS BASES

TASTE SOUR BITTER

FEEL STINGS SLIPPERY

REACTIONS YES / METAL NO / METALS

CONDUCTS ELECTROLYTE ELECTROLYTE

RELEASES H+ OH-

HOW DO WE MEASURE ACIDS AND BASES?

INDICATORSA SUBSTANCE THAT TURNS ONE

COLOR IN AN ACIDIC SOLUTION AND ANOTHER COLOR IN A

BASIC SOLUTIONSOME INDICATORS ARE:

LITMUS: DYE THAT COMES FROM A LICHEN

PHENOLPHTHALEIN: INDICATES ONLY BASES

UNIVERSAL INDICATOR: ACID, NEUTRALS, BASES CABBAGE JUICE: ACIDS, NEUTRAL, BASE