Title: Basic Atomic Structure
1Basic Atomic Structure
2Atoms are not solid spheres, they are composed of
. . . Subatomic particles
- Electron e-
- found outside the nucleus in orbitals
- Proton p
- found inside nucleus
- Neutron n0
- found inside nucleus
3Atomic Number
The number of protons defines the element
- Each element has a different atomic number 1, 2,
3, 4, 5, 6, 7, 8, 9, 10 . . . - The atomic number is equal to the number of
protons
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5Mass Numbera.k.a. Atomic Mass
- the mass of the atom is contained in the nucleus
- Masses of electrons are negligible
- it takes 1836 e- to equal the mass of 1p
or 1no
6- atomic mass p no
- 1 p 1 amu or 1/12 the mass of C atom
- 1 no 1 amu or 1/12 the mass of C atom
Carbon - 12 is the standard that all masses are
compared to. All other elements have relative
masses
7- How do you determine the number of neutrons in an
atom? - How do your determine the number of electrons in
an atom?
Atoms are neutral
8Atoms of the same element are not necessarily
alike . . .
Same atomic number different mass number
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10Isotopic Notation
- How many protons?
- How many neutrons?
a.k.a. H-1
11Isotopic Notation
- How many protons?
- How many neutrons?
a.k.a. H-2
12Isotopic Notation
- How many protons?
- How many neutrons?
a.k.a. H-3
13How is atomic mass of an element calculated?
- Atomic Mass of an Atom p no
- BUT since the number of neutrons in an atom can
vary . . . - Mass H 1 Mass H 2 Mass H 3
- The atomic mass is an AVERAGE mass of the
isotopes - BUT!!!!!! Is the mass of Hydrogen is 1.00794 and
not 2???????
14Weighted average
- Test grades 50
- HW 10
- Labs 40
- Test avg 85
- HW avg 90
- Lab avg 75
What is your MP average?
15Weighted Average of H
- 1amu x .9999 .9999
- 2amu x .0001 .0002
1.0001
Do NOT use division in a weighted average!!!!
16Electron Configurationsby principal E level
17Different E levels hold different s of e-
- E level 1 2 e-
- E level 2 8 e-
- E level 3 18 e-
- E level 4 32 e-
But NEVER more than 8 outermost
18e- in higher E levels have more E
19You can tell how many e- an atom hasAND which
energy level is being filled based on its
location in the periodic table
Number of electrons atomic number (p) of an
ATOM Period number where the outermost
electrons are
20Practice Problems
- What is the electron configuration of potassium?
- How many electrons does Phosphorus have in its
2nd E level? - How many e- does sodium have in its first
orbital? - How many e- does iron have in its 3rd E shell?
21Valence electrons
- Outermost number of electrons
- Never more than eight
22How many valence electrons?
- hydrogen
- potassium
- Sodium
- Lithium
- Magnesium
- Calcuim
- Barium
- Fluorine
- chlorine
- Neon
- Argon
- Krypton
23Notice anything?
- Elements (atoms) in the same group have the
same number of valence e- - The of valence e- corresponds to the last digit
of the group number
24Lewis Dot Structure
- Method of showing valence electrons
- Never more than 8 total
25Draw Lewis Dot diagrams
- lithium
- beryllium
- fluorine
- argon
26Electron Orbital Notation
- e- dont actually zoom around the nucleus on
little electron highways as seen in the Bohr
Model of the Atom. - THEREFORE
- true electron configuration isnt that easy!
27- Each principle orbital 1, 2, 3, 4 . . . is
divided into suborbitals s,p,d f - These are some shapes of the orbitals
28- s can hold 2 electrons
- p can hold 6 electrons
- d can hold 10 electrons
- The size of the suborbital is the same for any
one energy level - 3s, 3p, 3d are the same size
- 4s, 4p 4d are the same size but larger than the
3s
29- When writing orbital notation
- Orbital Suborbital of electrons
- or
- level sublevel number (oh my!)
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31Ions
32Ions are particles that carry a charge
- The charge an ion carries is the DIFFERENCE
between the p and e-
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34- Ions form because atoms want to have a full outer
energy level. - They will do this the easiest way possible.
- Na loses 1 electron Na1
- Cl gains 1 electron Cl-1
- Be?
- O?
- B?
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36Practice Problems
- What is the charge on an ion with 7p and 5e- ?
- What is the charge on an ion with an atomic
number of 8 and 5e-? - What is the charge on an ion with an atomic mass
of 35 if this atom has 18 neutrons and 18
electrons?
37Lewis Dot Structure
- Method of showing valence electrons
- Never more than 8 total
- For an ion CHARGE must be shown
38Draw Lewis Dot diagramsfor these ions
Dont show dots on the positive ions. All of
your negatives will have full dots. Always show a
charge.
- chloride
- phosphide
- fluoride
- calcium
- potassium
- aluminum
39Ground State vs. Excited state
- So far weve discussed e- in their ground state
40Ground State e-
- Definition e- occupy lowest possible energy
levels - Most stable electron configuration
- The electron configurations on your periodic
table show e- in their ground state - ex. 2 - 8 - 6
41Excited State e-
- Definition e- of an atom occupy higher E levels
when lower E levels are still vacant - ex. 2 - 7 - 7
- ex. 2 - 3 - 1
Can hold up to 8 here.
Can hold up to 8 here.
42Ground state 2 - 6Excited state 2 - 5 - 1
43Ground State to Excited State
44Excited State to Ground State
45Spectroscopy
- Emission lines of elements
- Bright line spectra
46- If you hold a prism to light you will see a
continuous spectrum of color. - ROYGBIV
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48Emission lines
- Visible light produced by electrons are confined
to narrow lines of color called bright line
spectra. - These emission lines are used to identify
elements - fingerprints
49Spectra of some elements
50THE END