Chemistry 11 – Early models of the atom 1

Structure of the Atom Democritus

• Developed the idea of ___________ • Thought “things” were made of atoms that have

different ___________

Aristotle

• Matter is made of different amounts of: ___________,___________,___________, and___________

John Dalton

• Elements are made up of very ______________________ atoms.

• An element is made up of a group of ___________atoms.

• A particular combination of specific types of atoms creates ______________________.

• Chemical reactions involve the re-shuffling of the atoms in a compound to make new compounds.

JJ Thomson

• Atoms contain ___________. • ______________________________________

______________________________________

______________________________________

__________________.

• “______________________” Model (Draw in the box)

atom

Shapes

earth fire water

air

small particles called

Atom identical

compound a chemical compound

A electrons

Atom = a ball of

positivelychargedmatrix w/ negative

electron charges ( e- I distributed

With TN

plum pudding

-0

-0

⑤

⑦

Chemistry 11 – Early models of the atom 2

Earnest Rutherford

• ___________experiment. • Most of the alpha particles (positively charged)

_______________________________________

___________________________.

! Atom is mostly ______________________ with a positively charged ___________. ! Nucleus contains almost all the mass of the atom and consists of ___________and ___________. ! The number of electrons surrounding the nucleus equals the number of protons in the nucleus, but electrons are much lighter than protons.

Niels Bohr

• Electrons had _______________________________

rather than being randomly distributed.

Quantum Model (Erwin Schrodinger)

• ____________________________________________, but they move around the nucleus in a random, but slightly predictable way.

Gold foil

-0-7⑤→# went through the atom, but some

bounced back

nucleus empty spacenucleus

← ispt n

pt n

①

⑦

'⑦

⑦

specific ,circular orbitals Lshell )

forplanetary model

Be e-

• → aye-

t •

•

Shri dinger showed e-

do not Q aroundnucleus

Cloud model

,

.

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Chemistry 11 – Atomic Theory Study Guide 1

Subatomic Particles: Electrons, Protons, and Neutrons Rutherford-Bohr Model: Definitions:

• Proton: ______________________________________________________________________ • Neutron: _____________________________________________________________________ • Electron: _____________________________________________________________________

Electron Proton Neutron

Symbol Charge

Mass (amu)

Atomic Number and Mass Number

Look at K for example: _________________

_________________ 19

K Potassium 39.098

_________________ _________________ Definition:

Atomic Number: � Of an element is the _______________________________________________ of its atoms. � No two elements have the _______ atomic number. � This number defines an ________________. � Increases by ______ as you go through the periodic table (refer to periodic table)

• Number of protons = _________________________________ (in neutral atoms)

Therefore, for K: 19 protons = ______ electrons in a neutral atom.

Subatomic particle in the nucleus that is tveiy chargedSubatomic particle in the nucleus that is neutralSubatomic - rely charged particle

# of ptsameelement

one

Atomic # = # of e-

19

Chemistry 11 – Atomic Theory Study Guide 2

So how do we fill the electrons in the shells?

• We follow the rule that certain shells can hold a certain number of electrons. 1st shell: ___ e-

2nd shell: ___ e-

3rd shell: ___ e-

4th shell: ____ e- …etc. We will only focus on the first 20 elements for now! Bohr Diagram for K: Ions: • Electrons can be ______________ from an atom if enough ____________ is applied to it.

For example, Na atom → Na+

sodium atom remove e- sodium ion 11 protons 11 protons 11 electrons 10 electrons

• Ions usually form as a result of atoms having _________________________________________. • +ve charged ions have ______ electrons, while –ve charged ions have __________ electrons

Bohr Diagram for Na+:

How do we find out the number of neutrons in an atom?

Definition: Mass number: � __________________________________________________________________.

� __________________________________________________________________.

= atomic mass

Total # of Pt and he

Chemistry 11 – Atomic Theory Study Guide 3

• By convention,

________ number 39 _________ number 19K

Example using K: How many neutrons are present in an atom of K that has mass number = 39? mass number = number of protons + number of neutrons number of neutrons = = =

Isotopes

• Not all atoms of the same element contain the same number of ___________ (remember

number of protons determines the identity of elements, NOT the number of neutrons). Definition:

Isotopes: � _______________________________________________________________________

Example: Carbon, C has three naturally occurring isotopes: C-12, C-13, C-14

Electron Configuration

Definition: Electron Configuration:

• _______________________________________________________________________

_______________________________________________________________________ 4 types of shells:

• s orbitals can hold ___ e- • p orbitals can hold ___ e- • d orbitals can hold ___ e- • f orbitals can hold ___ e-

Atoms having the same # of pt but not n

A description Ot Which orbitals in an atom contain

e- and how many e

-

are in each orbital .

Chemistry 11 – Isotope Calculation Study Guide !

!

Isotope Calculation Complete the following table:

!!!" or C-12 !!!" or C-13 !!!" or C-14

# of p+

# of e-

# of n

Atomic # (# of p+)

Mass # (# p+ + n)

Atomic mass Why is the mass number of element different from the atomic mass? The mass number is a whole number which represents sum of # of p+ and n but atomic mass is usually a decimal number which represents the molar mass of the element. Definition: Molar mass: ________________________________________________________________________ e.g., Molar mass of Cl is ____________. Where did this number come from?

• Scientific data tells us that there are two isotopes of chlorine Cl-35 and Cl-37. 75.77% of the element is Cl-35 and 24.23% of it is Cl-37.

!"#$%!!!"##! = ! !"#$%&'(!!"!!"#$#%& !!!(!"##!#!)

e.g., What is the molar mass of boron, given that there are:

• 18.8% of B-10 • Rest is all B-11

e.g., What is the molar mass of magnesium, given that there are:

• 78.99% of Mg-24 • 10.00% of Mg-25 • Rest is all Mg-26

!

Mass of one mole of particles . I