PreAP Chemistry Chapter 3
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PreAP Chemistry Chapter 3. Democritus was the early Greek philosopher who is credited with the concept of the atom (atomos) –which means invisible. Democritus was the early Greek philosopher who is credited with the concept of the atom (atomos) –which means invisible

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PreAP Chemistry Chapter 3

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Preap chemistry chapter 3

PreAP Chemistry Chapter 3


Preap chemistry chapter 3

Democritus was the early Greek philosopher who is credited with the concept of the atom (atomos) –which means invisible


Preap chemistry chapter 3

Democritus was the early Greek philosopher who is credited with the concept of the atom (atomos) –which means invisible

Law of Definite Proportions states that the elements in a specific compounds always contain the same proportions by mass.


Preap chemistry chapter 3

Law of Multiple Proportions states that if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers


Preap chemistry chapter 3

Dalton is an English school teacher who proposed the law of conservation of mass, the law of definite proportions, and the law of multiple proportions.


Preap chemistry chapter 3

Dalton is an English school teacher who proposed the law of conservation of mass, the law of definite proportions, and the law of multiple proportions.

He is also known as the Father of the Atomic Theory


Preap chemistry chapter 3

Dalton’s atomic theory

1.All matter is composed of very small particles called atoms


Preap chemistry chapter 3

  • Dalton’s atomic theory

  • All matter is composed of very small particles called atoms

  • Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in these properties.


Preap chemistry chapter 3

3.Atoms cannot be subdivided, created, or destroyed


Preap chemistry chapter 3

  • Atoms cannot be subdivided, created, or destroyed

  • 4.Atoms of different elements combine in simple whole-number ratios to form chemical compounds.


Preap chemistry chapter 3

  • Atoms cannot be subdivided, created, or destroyed

  • 4.Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

  • 5.In chemical reactions, atoms are combined, separated, or rearranged.


Preap chemistry chapter 3

  • Two aspects of Dalton’s atomic theory proven to be incorrect:

  • We now know atoms are divisible.


Preap chemistry chapter 3

  • Two aspects of Dalton’s atomic theory proven to be incorrect:

  • We now know atoms are divisible.

  • b. Atoms of the same element can have different masses.


Preap chemistry chapter 3

Atom --smallest particle of an element that retains the properties of that element.


Preap chemistry chapter 3

Two regions of an atom

1.Nucleus -- small region near the center of the atom.

Composed of two particles—the proton which is positively charged and the neutron which is neutral (zero) charged.


Preap chemistry chapter 3

2. Electron Cloud --composed of negatively charged electrons. It is very large in comparison to the nucleus.


Preap chemistry chapter 3

2. Electron Cloud --composed of negatively charged electrons. It is very large in comparison to the nucleus.

Subatomic particles—protons, neutrons, electrons


Preap chemistry chapter 3

2. Electron Cloud --composed of negatively charged electrons. It is very large in comparison to the nucleus.

Subatomic particles—protons, neutrons, electrons

Cathode Ray tubes — the instrument used in the discovery of the electron


Preap chemistry chapter 3

J. J. Thomson is the man credited with the discovery of the electrons in the late 1800’s


Preap chemistry chapter 3

J. J. Thomson is the man credited with the discovery of the electrons in the late 1800’s

Millikan discovered the mass of the electrons


Preap chemistry chapter 3

Knowledge of electrons led to two inferences about atomic structure:

1.Because atoms are electrically neutral, they must contain positive charge to balance the negative electrons.


Preap chemistry chapter 3

Knowledge of electrons led to two inferences about atomic structure:

1.Because atoms are electrically neutral, they must contain positive charge to balance the negative electrons.

2.Because electrons have so little mass, atoms must contain other particles to account for most of their mass


Preap chemistry chapter 3

Nucleus of the atom—discovered by Lord Ernest Rutherford


Preap chemistry chapter 3

Nucleus of the atom—discovered by Lord Ernest Rutherford

Gold foil experiment—actually done by Hans Geiger and Ernest Marsden


Preap chemistry chapter 3

  • Observations:

  • Majority of the alpha (α)particles penetrated foil undeflected.

  • b.About 1 in 20,000 were slightly deflected

  • c.About 1 in 20,000 were deflected back to emitter


Preap chemistry chapter 3

Conclusions: 1. Mass of the atom and the positive charge are concentrated in small regions called nucleus


Preap chemistry chapter 3

Conclusions: 1. Mass of the atom and the positive charge are concentrated in small regions called nucleus

2. Most of the atom is empty


Preap chemistry chapter 3

  • Conclusions: 1. Mass of the atom and the positive charge are concentrated in small regions called nucleus

  • Most of the atom is empty

  • 3.Magnitude of charge on the nucleus is different for different atoms


Preap chemistry chapter 3

4.Number of electrons outside the nucleus = number of units of nuclear charge (to account for the fact that the atom is electrically neutral)


Preap chemistry chapter 3

4.Number of electrons outside the nucleus = number of units of nuclear charge (to account for the fact that the atom is electrically neutral)

Atoms are electrically neutral because they contain equal numbers of protons and electrons


Preap chemistry chapter 3

1. What kinds of particles are being emitted by the radioactive source? What is their charge?


Preap chemistry chapter 3

  • What kinds of particles are being emitted by the radioactive source? What is their charge?

  • Alpha Particles, positive


Preap chemistry chapter 3

2. Toward what are the alpha particles being directed?


Preap chemistry chapter 3

  • Toward what are the alpha particles being directed?

  • Gold foil


Preap chemistry chapter 3

  • What happens when the charged particles strike the surface of the gold foil?


Preap chemistry chapter 3

  • What happens when the charged particles strike the surface of the gold foil?

  • Most go straight through

  • Some were slightly deflected

  • Some were greatly deflected


Preap chemistry chapter 3

  • What was the purpose of the fluorescent screen?


Preap chemistry chapter 3

  • What was the purpose of the fluorescent screen?

  • See where the alpha particles hit


Preap chemistry chapter 3

  • What did Rutherford conclude from this gold foil experiment regarding the amount of empty space in the atom? Why was he able to conclude this?


Preap chemistry chapter 3

  • What did Rutherford conclude from this gold foil experiment regarding the amount of empty space in the atom? Why was he able to conclude this?

  • Most of the atom is empty space because most of the particles went straight through.


Preap chemistry chapter 3

  • How does the deflection path of a charged particle that strikes the center of a gold atom differ from that path of a particle that passes only near the center?


Preap chemistry chapter 3

  • How does the deflection path of a charged particle that strikes the center of a gold atom differ from that path of a particle that passes only near the center?

  • If it hits the center it is deflected back to the emitter. If it passes near the center it is slightly deflected.


Preap chemistry chapter 3

  • Based on this experiment, where is most of the positive charge and mass of an atom found?


Preap chemistry chapter 3

  • Based on this experiment, where is most of the positive charge and mass of an atom found?

  • Nucleus – in the center


Preap chemistry chapter 3

  • What would have been observed if the positive charge of an atom had been thinly spread out throughout the atom?


Preap chemistry chapter 3

  • What would have been observed if the positive charge of an atom had been thinly spread out throughout the atom?

  • All the alpha particles would have behaved the same – gone straight through.


Preap chemistry chapter 3

Nuclear Forces the short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together


Preap chemistry chapter 3

Nuclear Forces the short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together

Mass of one proton = mass of neutron = mass of 1837 electrons


Preap chemistry chapter 3

Atomic number—the number of protons in the nucleus of the atom.


Preap chemistry chapter 3

Atomic number—the number of protons in the nucleus of the atom.

--number of protonsidentifies the

element and is equal to the number of electrons (of a neutral atom)

--symbol is Z


Preap chemistry chapter 3

Isotopes are atoms of the same element that have different masses because they have different numbers of neutrons but they still have similar chemical properties


Preap chemistry chapter 3

Isotopes are atoms of the same element that have different masses because they have different numbers of neutrons but they still have similar chemical properties

Mass number – approximate atomic mass of an atom (nucleus)

-- the number of protons + neutrons


Preap chemistry chapter 3

Isotopes of Carbon


Preap chemistry chapter 3

Isotopes of Carbon


Preap chemistry chapter 3

Nuclide is the general term for any isotope of any element


Preap chemistry chapter 3

Nuclide is the general term for any isotope of any element

Atomic Mass Unit (amu) is exactly 1/12 the mass of a carbon-12 atom


Preap chemistry chapter 3

Average atomic mass is the weight average of the atomic masses of the naturally occurring isotopes of an element.

Ave. Atomic mass = %abundace(mass of isotope 1) + %abundance(mass of isotope 2) +…..


Preap chemistry chapter 3

Moles

Mole (mol) is the amount of a substances that contains as many particles as there are atoms in exactly 12 g of carbon-12

(Mole comes from the German word for “pile”)


Preap chemistry chapter 3

Avogadro’s number – 6.022 ×1023 – is the number of particles in exactly 1 mole of a pure substance. Just as one dozen = 12 somethings, one mole = 6.022 ×1023 somethings.


Preap chemistry chapter 3

The mass of one mole of a pure substance (element or compound) is called the molar mass of that substance. The unit is


Preap chemistry chapter 3

Mole Review


Preap chemistry chapter 3

How many grams are in 2.0 mol Carbon?


Preap chemistry chapter 3

How many grams are in 2.0 mol Carbon?


Preap chemistry chapter 3

How many grams are in 2.0 mol Carbon?


Preap chemistry chapter 3

How many grams are in 2.0 mol Carbon?


Preap chemistry chapter 3

How many grams are in 2.0 mol Carbon?


Preap chemistry chapter 3

How many moles are in 0.58 g Al?


Preap chemistry chapter 3

How many moles are in 0.58 g Al?


Preap chemistry chapter 3

How many moles are in 0.58 g Al?


Preap chemistry chapter 3

How many moles are in 0.58 g Al?


Preap chemistry chapter 3

How many moles are equal to 1.20 x 1025 atoms of sodium? (Na)


Preap chemistry chapter 3

How many moles are equal to 1.20 x 1025 atoms of sodium? (Na)


Preap chemistry chapter 3

How many atoms are in 0.750 mol of zinc? (Zn)


Preap chemistry chapter 3

How many atoms are in 0.750 mol of zinc? (Zn)


Preap chemistry chapter 3

What is the mass in grams of 4.75 x 1024 atoms of silver? (Ag)


Preap chemistry chapter 3

What is the mass in grams of 4.75 x 1024 atoms of silver? (Ag)


Preap chemistry chapter 3

What mass of Antimony (SB) contains the same number of atoms as 9.0 g of aluminum?


Preap chemistry chapter 3

What mass of Antimony (Sb) contains the same number of atoms as 9.0 g of aluminum?


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