ch. 17 – properies of atoms and atomic structure i. structure of the atom symbols subatomic...
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Ch. 17 – Properies of Atoms and Atomic Structure
I. Structure of the Atom Symbols
Subatomic particles Electron cloud model
A. Chemical Symbols
Capitals matter! Element symbols contain ONE capital letter
followed by lowercase letter(s) if necessary.
Co vs. COMetal that
forms bright blue solid
compounds.
Poisonous gas.
B. Subatomic Particles
POSIT IVECHARG E
PROT ONS
NEUT RALCHARG E
NEUT RONS
NUCLEUS
NEG AT IVE CHARG E
ELECT RONS
AT OM
Most of the atom’s mass. Atomic Numberequals the # of...
in a neutral atom
NUCLEUS ELECTRONS
PROTONS NEUTRONS NEGATIVE CHARGE
POSITIVE CHARGE
NEUTRAL CHARGE
ATOM
B. Subatomic Particles
Quarks
• 6 types
• 3 quarks = 1 proton or 1 neutron He
A. Orbital
Region where there is 90% probability of finding an electron.
Can’t pinpoint the location of an electron.
Density of dots represents degree of probability.
A. Orbital
Orbitals have different shapes.
B. Energy Levels
Electrons can only exist at certain energy levels.
Low energy levels are close to the nucleus.
Each energy level (n) can hold 2n2 electrons.
C. Bohr Model Diagrams
Simplified energy levels using Bohr’s idea of circular orbits.
e-
e-
Maximum e-
Level 1 2e-
Level 2 8e-
Level 3 18e-
Level 4 32e-
Lithium Atomic #: 3 Mass: 7
# of p: 3 # of e: 3 # of n: 4
p
pn
nn n
p
e-
Can replace with:
3p4n
C. Bohr Model Activity
Choose a number between 1 & 18. Find your element by the atomic number you picked. Draw a Bohr Model diagram for your element.
• Round off the mass listed on the table and subtract the atomic # to find the # of neutrons.• Abbreviate the # of ‘p’ and ‘n’ in the nucleus.
Have a partner check your drawing. Repeat with a new element.
II. Masses of Atoms Atomic Mass
Mass Number
Isotopes
A. Atomic Mass
atomic mass unit (u)
1 u = 1/12 the mass of a 12C atom
1 proton = 1 u 1 neutron = 1 u
1 u = 1.67 10-24 g
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B. Mass Number
Sum of the protons and neutrons in the nucleus of an atom.
Always a whole number.
# of neutrons = mass # - atomic #
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C. Isotopes
Atoms of the same element with different numbers of neutrons.
C126Mass #
Atomic #
Isotope symbol:
“Carbon-12”
C. Isotopes
© Addison-Wesley Publishing Company, Inc.
C. Isotopes
Average Atomic Mass• reported on Periodic Table• weighted average of all isotopes
atoms of # total
atoms) of )(## (massatoms) of )(## (mass
Avg.AtomicMass
Avg.AtomicMass
C. Isotopes
EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37.
atoms 10
atoms) u)(2 (37atoms) u)(8 (3535.4 u
III. The Periodic TableMendeleev
Mosely
Organization
A. Dmitri Mendeleev
Dmitri Mendeleev (1869, Russian)
• Organized elements by increasing
atomic mass.
• Predicted the existence of
undiscovered elements.
B. Henry Mosely
Henry Mosely (1913, British)
• Organized elements by increasing
atomic number.
• Fixed problems in Mendeleev’s
arrangement.
A. Metallic Character
1
2
3
4 5
6
7
Metals Nonmetals Metalloids
B. Table Sections
1
2
3
4 5
6
7
Representative Elements Transition Metals Inner Transition Metals
B. Table Sections
1
2
3
4
5
6
7
Lanthanides - part of period 6
Actinides - part of period 7
Overall Configuration
C. Columns & Rows
1
2
3
4 5
6
7
Group (Family) Period
C. Terms Valence Electrons
• e- in the outermost energy level• these determine the properties of
the elements• Elements in the same group have
the same # of valence electrons
D. Periodic Trends Group # = # of valence e- (except He)
• Families have similar reactivity Period # = # of energy levels
1A
2A 3A 4A 5A 6A 7A
8A
E. Dot Diagrams
Dots represent the valence e-. EX: Sodium
EX: Chlorine