Chapter 3 - Atoms: The Building Blocks of Matter

Democritus

Who coined the term "atom", which means "indivisible"?

Aristotle

Who did not believe in atoms and believed that all matter was continuous?

Law of Conservation of Mass, Law of Definite Proportions, Law of Multiple Proportions

What are the 3 laws the describe how matter behaves in chemical reactions?

Law of Conservation of Mass

Law that states that matter is neither created or destroyed during ordinary chemical reactions of physical changes.

matter, created, destroyed, chemical, physical

Law of Conservation of Mass - states that _____________________ is neither _____________________ or _____________________ during ordinary _____________________ reactions or _____________________ changes.

Law of Multiple Proportions

Law that 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 small ratio of whole numbers.

elements, proportions, size

Law of Definite Proportions - states a chemical compound contains the same _________________ in exactly the same ______________________ by mass regardless of the ___________ of the sample or source of the compound.

Law of Definite Proportions

Law that states a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.

different, elements, small, whole

Law of Multiple Proportions - states that if two or more _____________________ compounds are composed of the same two _____________________, then the ratio of the masses of the second element combined with a certain mass of the first element is always a _____________ ratio of _____________ numbers.

atoms, size, mass, properties

Summary of Dalton's Theory:

1) ALL matter is composed of extremely small particles called _____________. (✓)

2) Atoms of a given element are identical in __________, ____________, and other ____________; Atoms of different elements differ in size, mass, and other properties. (x)

3) Atoms cannot be subdivided, created, or destroyed. (x)

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. (✓)

differ, subdivided, different, combined

Summary of Dalton's Theory:

1) ALL matter is composed of extremely small particles called atoms. (✓)

2) Atoms of a given element are identical in size, mass, and other properties; Atoms of different elements ______________ in size, mass, and other properties. (x)

3) Atoms cannot be ______________, created, or destroyed. (x)

4) Atoms of ______________ elements combine in simple whole number ratios to form chemical compounds. (✓)

5) In chemical reactions, atoms are ______________, separated, or rearranged. (✓)

divisible, masses, matter, properties

Modern Atomic Theory:

a) Atoms ARE _____________________ into even smaller pieces (protons, neutrons, electrons)

b) A given element can have atoms with different _______________ (isotopes).

c) ALL _______________ is composed of atoms

d) Atoms of any one element differ in ____________________ from atoms of another element.

Atom

Smallest complete part of an element that can exist alone or in combination with others.

Nucleus

Part of an atom:

Positively charged central part of the atom

- Very dense

1 x 10^-13 cm in diameter

Electron cloud

Part of an atom:

Negatively charged region around the nucleus where electrons exist

(electrically) neutral

What is the charge of all atoms?

Total negative charge of the electron cloud

The total POSITIVE charge of the NUCLEUS of an atom equals what?

electrons

What are located in the electron cloud?

negative, light, shells, energy levels, equal

Electrons:

- __________________ charge

- Very _________________ particles (9.109 x 10^-28 g); (1/1837th the mass of a proton)

- They exist in regions called _________________ or _________________ ___________________

- They are always _______________ to the number of protons in the nucleus

*All electrons are IDENTICAL*

Shell/Energy level

Regions of probable locations of electrons [K-L-M-O-P-Q]

*All electrons are IDENTICAL*

JJ Thomson, Robert Millikan

Discovery of the Electron:

1) ________________________ - cathode-ray tube experiments measured the charge-mass ratio of an electron

2) ________________________ - oil drop experiment measured the charge of an electron

*Both discovered enabled scientists to determine the mass of an electron*

cathode-ray tube, charge-mass

Discovery of the Electron:

1) J.J. Thomson - ___________________________________ experiments measured the _______________________ ratio of an electron

2) Robert Millikan - oil drop experiment measured the charge of an electron

*Both discovered enabled scientists to determine the mass of an electron*

oil drop, charge, mass

Discovery of the Electron:

1) J.J. Thomson - cathode-ray tube experiments measured the charge-mass ratio of an electron

2) Robert Millikan - ________ ______________ experiment measured the ________________ of an electron

*Both discovered enabled scientists to determine the _____________ of an electron*

Ernest Rutherford, 1911

Which scientist discovered the nucleus and in what year?

Gold Foil Experiment

What experiment did Ernest Rutherford conduct in 1911 that led to the discovery of a very DENSLY packed bundle of matter with a POSITIVE charge (nucleus)?

protons, neutrons

What are the nuclear particles?

positive, heavy, electrons, nucleus

Protons (p+):

a) _______________ charge (equal in magnitude to the charge of an electron)

b) Relatively _______________ particles (1.673 x 10^-24 g)

c) Always EQUAL the number of _______________

d) Found in the _______________

neutral, proton, nucleus

Neutrons (n^0):

a) No electrical charge (________________)

b) Same weight as a ________________ (1.675 x 10^-24 g)

c) Found in the ________________

repel, attract

LIKE charges ________________ and UNLIKE charges ________________.

Nuclear Forces

Short range p+ -- p+ , p+ -- n^0 , n^0 -- n^0, attraction forces which hold the nucleus together

- The nucleus accounts for most an atom's mass, while most of an atom's volume is due to the size of its electron cloud

nucleus, mass, volume, cloud

Nuclear forces - short range p+ -- p+ , p+ -- n^0 , n^0 -- n^0, attraction forces which hold the _______________ together

- The NUCLEUS accounts for most an atom's __________, while most of an atom's ______________ is due to the size of its electron ___________

Atomic Number (Z)

Refers to the number of protons found in the nucleus of an element

*In the periodic table, the elements are placed from left to right in order of INCREASING atomic numbers*

*____________________________ = # of protons = # of electrons*

Mass Number

Refers to the total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of the same element that have different masses; They differ in their number of NEUTRONS

hyphen, nuclear, mass, atomic

Methods of Designating Isotopes:

1. _______________ Notation: Hydrogen -- 3 (3 refers to the mass number)

2. ________________ Symbol: mass # is superscript and the atomic # if subscript

*Number of neutrons = ___________ # - ___________ number

Atomic Mass Unit (AMU)

A unit of the relative mass scale.

1 amu = 1/12 of C-12 = 1.660 540 2 x 10^-24 g

C-12

Which element is used to compare the atomic mass of any atom?

1/12

1 amu = __________ of C-12 = 1.660 540 2 x 10^-24 g

Atomic Mass

The mass of an atom expressed in atomic mass units.

Average Atomic Mass

The sum of the atomic masses of EACH isotope multiplied by the DECIMAL of its percentage abundance.

Avogadro's Number

The number of atoms there are in exactly 12 grams of carbon-12.

**6.022 x 10^23**

6.022 x 10^23

What is Avogadro's Number?

Mole (mol)

The amount of substance that contains the Avogadro's number of chemical units

- The SI base unit used to measure the amount of a substance

**1 ___________________ = 6.022 x 10^23**

Molar Mass

(Gram-atomic-weight): the mass in GRAMS of one mole of an element

- Contain equal numbers of atoms
- Has the units of grams per mole (g/mol)