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CHEM 131 Lecture > Ch 3 - The Evolution of Atomic Theory > Flashcards

Ch 3 - The Evolution of Atomic Theory Flashcards

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0
Q

Leucippus and Democritus ~450 BCE

A

Defined the atom as the point at which matter can no longer be subdivided. Matter was made if tiny, discrete indivisible particles called atoms.

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1
Q

Aristotle ~384 BCE

A

Proposed that all matter is composed of four elements and all matter is a continuous (infinitely divisible), not atomistic

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2
Q

Law of conservation of mass

A

When a reaction takes place, matter is neither created or destroyed

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3
Q

Law of constant proportion

A

Multiple samples of any pure compound always contain the same percent by mass of each element making up the compound

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4
Q

Percent by mass equation

A

% mass = mass of element x 100
——————–
total mass of compound

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5
Q

Law of multiple proportions

A

Elements may combine in more than one set of proportions, with each set corresponding to a different compound

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6
Q

Dalton’s atomic theory

A

1) All matter is made up of atoms
2) Atoms can neither be created not destroyed
3) Atoms of a particular element are alike
4) Atoms of different elements are different
5) A chemical reaction involves the union or separation of individual atoms

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7
Q

Modern modifications of Dalton’s atomic theory

A

1) Dalton assumed atoms to be indivisible. Not quite true (electrons, neutrons, protons).
2) Dalton assumed that all the atoms of a given element were identical in all aspects, but we know ions are an exception to this rule.
3) The numbers of each kind of atom in simple compounds usually form a simple ratio.
4) Unmodified for chemical reactions. Atoms are broken apart in nuclear reactions.

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8
Q

Ball and hook model

A

Different size balls represent different atom types; different types have different numbers of hooks representing bonding

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9
Q

Discovery of the electron

A

1897: J. J. Thomson determined the charge using the mass ratio if cathode ratio

Electron was very small and lightweight (1/1836 mass of H atom)

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10
Q

Discovery of the proton

A

1907: J. J. Thomson and E. Goldstein

Much heavier than the electron (~same mass as a H atom)

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11
Q

Discovery of the neutron

A

1932: James Chadwick

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12
Q

Electron mass

A

9.1 x 10^-28 g

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13
Q

Plum-pudding model

A

Positive “pudding” base with free-floating negative electrons in it

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14
Q

Rutherford’s gold foil experiment

A

Fired alpha particles at metal foils and a glass substrate covered in zinc sulfide to monitor the alpha particles. Surprised by the large angles of deflection by some if the particles (disproved the plum-pudding model)

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15
Q

Characteristics of a nucleus

A

1) Atom contains dense center called nucleus
2) Nucleus is essential to the entire Aron’s mass
3) Nucleus is positively charged
4) Electrons are disbursed in the empty space if the atom surrounding the nucleus

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16
Q

Proton mass

A

1.67262 x 10^-24 g

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17
Q

Proton charge

A

+1.60 x 10^-19 C

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18
Q

Electron charge

A

-1.60 x 10^-19 C

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19
Q

Atomic number (Z)

A

The number of protons in the nucleus; determines the identity of the atom

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20
Q

Mass number

A

Protons + neutrons

21
Q

Isotopes

A

Atoms with the same number of protons (same element), but different numbers if neutrons (different mass numbers).

Exhibit identical chemical properties.

22
Q

Isotope symbol

A

Shows the mass number and the atomic number (often omitted)

23
Q

Atomic mass

A

The actual mass of any atom

24
Q

Atomic mass units (amu)

A

1 amu = (1/12) the mass of a carbon-12 atom

1 amu = 1.66054 x 10^-24 g

25
Q

Relative atomic mass

A

Measures how massive an atom is in comparison to a carbon-12 atom

26
Q

Weighted average of atomic mass

A

Weighted average of the isotope masses

27
Q

Law of Octaves

A

Elements that are eight elements apart by mass react in similar manners.

Also known as chemical periodicity or periodic behavior.

28
Q

Law of Mendeleev

A

Properties of the elements recur in regular cycles (periodically) when elements are arranged in order of increasing atomic mass.

29
Q

Periods

A

Horizontal rows on the periodic table if elements

30
Q

Groups

A

Vertical columns of the periodic table of elements

31
Q

Main-group elements

A

Groups 1,2, 13-18

32
Q

Noble gases

A

Group 18

33
Q

Transition metals

A

Groups 3-12

34
Q

Lanthanides

A

Top row if the lower section of the table (not numbered)

35
Q

Actinides

A

Bottom row if the lower section of the table (not numbered)

36
Q

Metals

A

Metallic luster, conduct heat and electricity, malleable, and ductile

(Ex: sodium and copper)

37
Q

Non metals

A

Dull luster, good insulator, nonconductors, and brittle in the solid state.

(Ex: sulfur and bromine)

38
Q

Metalloids

A

Demonstrate properties of both metals and nonmetals; used as semiconductors.

(Ex: silicon and arsenic)

39
Q

Group names

A 
Group 1 (1A): alkali metals
Group 2 (2A): alkaline earth metals
Group 16 (6A): chalcogens 
Group 17 (7A): halogens
Group 18 (8A): noble gases
40
Q

Alkali metals

A 
Lithium (Li)
Sodium (Na)
Potassium (K)
Rubidium (Rb) 
Cesium (Cs) 
Francium (Fr)
41
Q

Alkaline earth metals

A 
Beryllium (Be)
Magnesium (Mg)
Calcium (Ca)
Strontium (Sr)
Barium (Ba)
Radium (Ra)
42
Q

Halogens

A 
Fluorine (F)
Chlorine (Cl)
Bromine (Br)
Iodine (I)
Astatine (At)
43
Q

Chalcogens

A 
Oxygen (O)
Sulfur (S)
Selenium (Se)
Tellurium (Te)
Polonium (Po)
44
Q

Noble gases

A 
Helium (He)
Neon (Ne)
Argon (Ar)
Krypton (Kr)
Xenon (Xe)
Radon (Rn)
45
Q

Law of octaves adjustments

A

Works well only when considering the main-group elements

46
Q

Ions

A

Charges atoms or groups if atoms

47
Q

Anions

A

Negatively charges ions (gain electrons)

48
Q

Cations

A

Positively charged ions (loses electrons)

49
Q

First ionization energy

A

Minimum amount of energy it takes to completely remove an electron forming a 1+ ion.

Exhibits periodicity similar to chemical properties. Metals exhibit lower values than nonmetals

CHEM 131 Lecture (3 decks)

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