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Chem3: Atoms & Moles

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Stanley Eaton

on 20 September 2016

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Transcript of Chem3: Atoms & Moles

Atoms and Moles
Vocabulary
Atoms
Describe three laws supporting the existence of atoms
Atoms are the smallest units of the elements. Atoms contain a nucleus of protons and neutrons with clouds of electrons surrounding it.
Protons
Neutrons
Law of definite proportions
a chemical compound always contains the same elements in exactly the same proportions by weight and mass (
p.75
)

Law of conservation of mass
: mass isn't changed by chemical reactions (
p.76
)

Law of multiple proportions
: 2 different compounds made of the same 2 elements show simple ratios: i.e. NO and NO2 (
p.77
)

Electrons
: small, negatively charged particles found around the nucleus; discovered by Thompson in 1897 (
p.80
)

Nucleus
: dense, massive, positively charged central part of an atom; made of nucleons (
p.81
)

Protons
: small, positively charged nucleons found in the nucleus; discovered by Rutherford in 1909 (
p.82
)

Neutrons
: small, uncharged particles found in the nucleus; discovered by Joliot-Curie and Chadwick in 1932 (
p.82
)

Atomic Number
: # of protons in an atom (
p.84
)

(Atomic) Mass Number
: # of nucleons in an atom (
p.85
)

Isotopes
: atoms of the same element that differ in mass number because they have different numbers of neutrons (
p.88
)

Orbitals
: number of protons in an atom (
p.91
)
??
Electrons
How Atoms Compose Substances
Law of Definite Proportions
This law states that chemical compounds contains the same elements in the same ratio by weight or mass, regardless of size or source of samples.
Law of Conservation of Mass
This law states that mass is not changed when a chemical reaction occurs.
The Atomic Theory states that
atoms are the building blocks
of all matter.
Law of Multiple Proportions
This law states that when the same two elements compose
two or more different compounds, the ratio of the mass of
the second element is always a ratio of small whole numbers.
Electromagnetic Spectrum
:
a broad range of wavelengths used to measure distance between two consecutive troughs of a wave (
p.92
)

Ground State
: when an electron is in its state of lowest possible energy (
p.94
)

Excited State
: the position an electron is at when it gains energy (
p.94
)

Quantum Number
: a number that shows the properties of an electron (
p.95
)

Pauli exclusion principle
: this states that only two electrons can occupy a single orbital and cannot be in the same energy state (
p.96
)

Electron Configuration
: A diagram that shows arrangement of electrons in an atom (
p.96
)

Aufbau principle
: this states that electrons start filling up orbitals at the lowest quantum value (
p.97
)

Hund's rule
: this states that before electron pairing, orbitals of the same n and l quantum numbers have one electron (
p.98
)

Mole
: The number of atoms in exactly 12 grams of carbon-12 (
p.101
)

Molar Mass
: Mass in grams of one mole of a substance (
p.101
)

Avogadro's Number
: Equal to 6.022X10^23, the number of particles in 1 mol (
p.101
)
Electron Configuration
Electrons are ordered according to four quantum numbers.
The
principal
quantum number represents the main energy level the electron occupies, indicating size.
The
angular momentum
quantum number indicates the shape of a particular sublevel.
The
magnetic
quantum number indicates which orbital in a sublevel.
The
spin
quantum number is which way the electron spins
Sublevels are named s, p, d, or f. The s sublevel holds one orbital, the p sublevel holds three, the d sublevel five, and the f sublevel holds seven. Each orbital can hold two electrons.
Aufbau
I am the intruder.
Objectives
Define and use mols
Write electron configurations using Pauli exclusion and aufbau
List the quantum numbers and explain their significance
Calculate # of p+, n0, and e- in atoms, isotopes, and ions
Define atomic number & mass number
Compare models of the atom
Types of subatomic particles
Protons and neutrons are nucleons, or nuclear particles. Nucleons are about 2000 times as heavy as electrons.
Nucleons
Describe properties of subatomic particles
A substance known as basic copper carbonate (a) occurs in nature as the mineral malachite, (b) forms as a patina on copper roofs and bronze statues, and (c) can be synthesized in the laboratory. Regardless of its source, basic copper carbonate always has the same composition.
Counting Subatomic Particles
Atomic number:
# of protons
Element's Symbol
Mass number: number of nucleons
To find the number of:
1) protons = atomic number
77
2) electrons = protons
77
3) neutrons = (rounded) atomic mass - atomic number
192-77=115
Ions
Isotopes
Ions have the same number of nucleons as normal atoms but have a different number of electrons. Count the charge and
subtract
it from the atomic number to find the number of electrons.
Isotopes have the same number of protons and electrons as normal atoms but have a different number of neutrons.
Subtract
the atomic number from the atomic mass (no rounding needed!).
Ir
2+
Ir
-
77-2=75
77-(-1)=78
Models of the Atom
Dalton's
Model
Democritus'
Model
Thompson's
Model
Rutherford's
Model
Bohr's
Model
de Broglie's
Model
Atomic Orbitals
Counting Atoms
Mols
Mass
# of particles
divide by formula mass
multiply by formula mass
formula mass is the mass of the atom, molecule, or formula unit
divide by Avogadro's number
multiply by Avogadro's number
Avogadro's number is 6.022 x 10
23
Flame
Test
negative charge
symbolized e
around nucleus
small mass
discovered by Thompson
positive charge
symbolized p
nucleon
mass = 1 amu
discovered by Rutherford
-
+
no charge
symbolized n
nucleon
mass = 1 amu
discovered by Joliot-Curie and Chadwick
0
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