Matter & Energy
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Transcript of Matter & Energy
Matter & EnergyFoundations of the Natural World
Matter• If it exists, it’s matter▫You, a rock, oxygen…▫has mass; takes up space
(volume)•Fundamental unit: the atom•Atoms vary by # of protons ▫ each a different element
•Organized into the periodic table
•Can be changed, yet is always conserved
Energy•Makes things happen▫Do work▫Reorganize matter
•Comes in different forms▫in the chemical bonds of the
food we eat▫radiant energy from the sun
•Can be changed, yet is always conserved
Mass is energy? • In the early 20th century,
scientists hypothesized that mass and energy are linked.
•Albert Einstein provided the mathematical evidence with his famous equation, E = mc2
▫"E" ="energy," ▫"m" denotes "mass" ▫"c" is the speed of light
Atomic structure
New Boys
Pro’s
Elected ones
WKRP atomic structure.webloc
the ‘hood
Atomic structure
neutron
Proton: + chargeatomic nucleus
Electron: - charge
Sub-atomic structure
Up quark charge +2/3
Down quark charge -1/3
Some sub-atomic particles have sub-particles themselves!
e- ? Its a fundamental particle
Do the math!p = 2 ups, 1 downn = 1 up, 2 down
Unstable nuclei
• changes the number of protons • changes the element • a radioactive atom (more in C/D IS
year)
Potential problem in nucleus : like charges (++) repel
Neutrons break up charge; if they can’t, particles are ejected
Electrons orbit the nucleus
Orbit model vs Orbital model
• Negative electrons orbit the positive nucleus The first - nearest the nucleus - can hold up to 2 e-
The others hold 8e- or more , but are ‘full’ once they have 8
Element info
element
atomic number = protons infer electrons If p <> e, then an ion
symbol
atomic mass = nuclear mass # protons + neutrons why .003? Isotopes!
*a.m.u. = 1 atomic mass unit number of nuclear particles = mass number
Isotopes of H
1 a.m.u.* 2 a.m.u. 3 a.m.u.
Isotopes vary in # of neutrons
Electron dot model* – shows valence e-
*aka Lewis dot
6 e-
2•8•4 valence e-
The number of e- in the outermost orbitDetermines if the atom will form bonds
10 e-
2•8•8 valence e-
12 e-
2•18•2 valence e-
6 valence e • accepts 2 • -2 oxidation #
2 valence e- • donates 2 • +2 oxidation #
Determines which atoms are likely to bond with which other atoms is the outer orbit more empty, or more full?
It’s a match!
Oxidation Number determined by valence e-
Periodic patterns
Groups - Same valence/oxidation #
Periods - Same # shells/orbits
No stable isotopessynthetic
the element song
Periodic patterns
Periods - Same # shells/orbits
No stable isotopessynthetic
the element song
Ionic bonds
Valence stability achieved by moving an electron to another atom Creates charge imbalanceAtoms become ions
Positive & negative ions attracted to one another
Oppositely charged ions form an ionic bond
11 p+ 17 p+ 11 e- 17 e-
11p+ 17P+
10 e-18 e-
+
-
Oxidation: +1 -1
p+ to e- ratio: 11:10 17:18
Another view
Covalent bonds
Share electronsElectrons orbit both atoms equally
Atoms have an equal attraction to the electrons
Polar covalent bonds
Electrons more attracted to one atom type – reflects electronegativity
Share e- unequally
-+
+
Result? Regions of molecule are weakly positive and negative
Ionic Bonds
metal with non- metal very different valences electrons donated/accepted ex: NaCl
NaCl
go either way
17
Covalent BondsNon-metal with non-metalsimilar valenceselectrons shared ex: CO2
C O
go either way
4 6