Properties of Atoms 1. SC3 Students will use the modern atomic theory to explain the characteristics...

PropertieProperties of s of

AtomsAtoms

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SC3 Students will use the modern atomic theory to explain the characteristics of atoms.

a. Discriminate between the relative size, charge, and position of protons, neutrons, and electrons in the atom.

b. Use the orbital configuration of neutral atoms to explain its effect on the atom’s chemical properties.

c. Explain the relationship of the proton number to the element’s identity.

d. Explain the relationship of isotopes to the relative abundance of atoms of a particular element.

e. Relate light emission and the movement of electrons to element identification.

Atomic Structure Goals

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Matter

SubstanceMixture

ElementCompound

This will be our FOCUS

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What is an What is an Element?Element?•One of the ~116 known One of the ~116 known

“Pure”, un-cutable “Pure”, un-cutable substances….substances….that still retain that still retain the properties of that substance.the properties of that substance.

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What is an Atom?•Smallest piece of matter Smallest piece of matter

that that still retains the still retains the propertiesproperties of that of that matter.matter.

•What are they composed What are they composed of?of?

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Timeline

Bohr Model- electrons are found only in specific circular paths, or orbits, around the nucleus.Electron Cloud Model: Probable locations of electrons.MODERN:

Quantum Mechanical Model: Mathematical model describing the behavior of electrons and energy of electrons in various locations around the nucleus.

Subatomic Subatomic ParticlesParticles• Protons• Neutrons• Electrons

NucleusNucleus

7 Atomic Structure

8 Atomic Structure

What makes one element different from another element?

Number of protons.

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Atomic Structure

Rutherford’s Gold Foil experiment led to the discovery of a positive

nucleus.

10 Atomic Structure

ProtonsProtons•Positive ChargePositive Charge•The number of protons determines which The number of protons determines which

element it is.element it is.•All elements have different numbers of All elements have different numbers of

protonsprotons•1 amu1 amu•Composed of quarksComposed of quarks

11 Atomic Structure

Neutron

• Neural charge• Located in the nucleus• 1 amu

• Composed of quarks

Atomic Structure

•Smallest Smallest subatomic subatomic particle.particle.

•1/1800 the 1/1800 the mass of a mass of a proton.proton.

•Orbit nucleus.Orbit nucleus.•Negative Negative ChargeCharge

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Atomic Structure

•Electrons are Electrons are found in found in different levels different levels around the around the nucleus.nucleus.

•These are These are called Energy called Energy Levels or shells.Levels or shells.

•Each energy Each energy level also has level also has “sublevels” or “sublevels” or orbitalsorbitals

13 Atomic Structure

14 Atomic Structure

Electrons Electrons are found are found

in the in the

Electron Electron cloudcloud

surroundinsurrounding the g the

nucleus.nucleus.

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15 Atomic Structure

Each Energy Level Can Hold Each Energy Level Can Hold A Certain Number of A Certain Number of

Electrons!Electrons!Only Only TWO TWO on on the the first first levellevel!!

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Atomic Structure

Different atoms have different Different atoms have different numbers of electrons!numbers of electrons!

Eight Eight on on the the 22ndnd

Each Energy Level Can Hold Each Energy Level Can Hold A Certain Numbers of A Certain Numbers of

Electrons!Electrons!

1717 Atomic Structure

2n2

18 Atomic Structure

Atomic Structure

• Atomic Atomic NumberNumber

• Number of Number of ProtonsProtons

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1

•Atomic MassAtomic Mass

•Sum of Sum of Protons & Protons & NeutronsNeutrons

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The # of Protons determines the identity of an element. All elements have

different number of protons.

Atomic Structure

How can I find out how How can I find out how many electrons an atom many electrons an atom

has?has?•Atom= neutral•So, the number of protons = electrons.

•Atomic number tells you the number of protons.................

•So, it also tells you the number of electrons!

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Atomic Structure

• Practice with a friend…………

Quantum Mechanical Model• Based on quantum theory, which says matter also

has properties associated with waves.

• According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. This is known as the

Uncertainty Principle.

• This model of the atom uses complex shapes of orbitals (sometimes called electron clouds)

– Orbitals: volumes of space in which there is likely to be an electron.

So, this model is based on probability rather than certainty.

Atomic Orbitals• An atomic orbital is a region of space in which there

is a high probability of finding an electron.

• Energy levels of electrons are labeld by principal quantum numbers (n).

• Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

• Different orbitals have different shapes.

Quantum Numbersn, l, m, s

•Describing electron locations•4 quantum number.•1st-Principle Quantum # = n

–Which energy level the e- is in.– n= 1-7 (there are only 7 energy levels)

•Max # formula= 2n2

• the larger the value of n, the farther away from the nucleus and the higher the energy of the electron.

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2nd quantum number= l• Describes the shape (orbital)• Shapes: s, p, d, f• Each shape “sublevel”

can only have 2 electrons.

• Max electrons in each sublevel:– s=(1x2)2, p=(3x2)6, d=(5x2)10,

f=(7x2)14 # of sublevels

s & p

S (1),p (3), d (5)

# of sublevels (shapes)

F (7)

• 3rd quantum number= m–Describes orientation in space

–x, y, z• 4th quantum number= s

–Describes the spin of the e in the orbital

–Clock or counterclock

• Brain Break• Clip

1. Aufbau Principle: e-

occupy orbitals of the lowest energy first.

22Orbital Filling Diagrams (3 rules)

p.133 text

• Hund’s Rule: one electron in each orbital, then electrons pair up with opposite spins.

• Pauli Exclusion Principal: An orbital may have no more than 2 electrons. 2 e- cannot have the same spin in the same orbital.

22Orbital Filling Diagrams

• Practice:• H, C, Na, S, Ar, K.

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Blocks and Sublevels• We can use the periodic table to predict which sublevel is

being filled by a particular element.

Electron Configuration Notation24

Practice: Write the electron configuration notation.

Name Atomic Number Electron Configuration

• Oxygen 8 1s2 2s22p4

• Aluminum13 1s2 2s22p63s23p1

• Chlorine 17 1s2 2s22p63s23p5

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Electrons and Light Emission• When atoms absorb

energy, electrons move into higher energy levels (excited state).

• When the return to their ground state, the lose energy by emitting light.

• The light emitted is a mixture of a specific frequencies.

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• A quantum of energy is the amount of energy required to move an electron from on energy level to another energy level.

• The higher the ground state, the less energy it take to move to a higher energy level.

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Electrons & Light Emission

• Each frequency is a different color.

• When the frequencies are passed through a prism, the colors are separated & an atomic emission spectrum is created for that element.

• Larger “jump”- more energy-more towards the blue side

• Smaller “jump”- less energy-more towards the red side

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• The flame test is used to visually determine the identity of an unknown metal or metalloid ion based on the characteristic color the salt turns the flame of a bunsen burner

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IsotopesIsotopes are atoms that have the same number of protons and differ only in the

number of neutrons.

Most isotopes are stable but radioactive isotopes are unstable and break down into more stable forms by emitting particles and

energy (radiation). Radiation can be detected, so radioactive isotopes are useful as labels in scientific

research and medical diagnostic procedures.

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Let’s Do some practice problems

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• How do you find this number?

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Calculating Average Atomic Mass

Percent(%) abundance of isotopes

Weighted average= Mass of each isotope x %

abundance of that element

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Atomic Mass of Magnesium

Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% = ______

25Mg = 25.0 amu 10.13% = ______

26Mg = 26.0 amu 11.17% = ______

Atomic mass (average mass) Mg = 24.3 amu Mg24.3

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Practice• Gallium is a metallic

element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the avg. atomic mass of gallium?

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• A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?

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Counting Atoms

• The Mole

• For a given molecule (atom), one mole is a mass (in grams) whose number is equal to the atomic mass of the molecule (atom)

The Mole

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A counting number (like a dozen)

Avogadro’s number (NA)

1 mol = 6.02 1023 items

What is the Mole?

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The Mole

–1 mole of molecules has a mass equal to the molecular weight in grams.

–A mole of carbon-12 atoms has a mass of just 12 g.

• How many Atoms is that???• 1 mole = 6.022 x 1023 atoms

Avogadro's number Amedeo Avogadro (1776-1856)

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Molar Mass

Mass of 1 mole of an element or compound.

Atomic mass tells the... atomic mass units per atom (amu) grams per mole (g/mol)

1 atom of C = 12.01 amu 1 mol of C = 12.01 g

Round to 2 decimal places

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lithium

aluminum

zinc

6.94 g/mol

26.98 g/mol

65.39 g/mol

Molar Mass Examples

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Molar Conversion Examples How many grams of iron are in

2.25 mol of iron?

2.25 mol Fe 55.85 g Fe

1 mol Fe= 126 g Fe

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Molar Conversion Examples How many moles of calcium are

in 5.0 g of calcium?

5.0 g Ca 1 mol Ca

40.08 g Ca= 0.12 mol Ca

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Examples • 1 mole of Na is the number of atoms in 22.9898g

• 22.9898g is the molar mass

• 1 mole H2O is the number of molecules in 18.015 g H2O

• 1 mole H2 is the number of molecules in 2.016 g H2. Practice:1. How many atoms are in 1 mol of H?2. What is the mass of 1 mol of H?3. How many atoms are in 2 mole of H?4. What is the mass of 2 mol of H?

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More Practice:5. Convert 589 g of Au to moles. 6. Convert 344 grams of Fe to moles.7. What is the mass of 3 moles of KOH?

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Mole Day is October 23rd!