1. 2.1 – The Nature of Matter

2. Atoms Basic unit of matter Particle Charge Location in Atom Proton
Comes from word atomos, meaning “unable to be cut” further
Consist of subatomic particles
Particle
Charge
Location in Atom
Proton
Positive
Nucleus
Neutron
Neutral
Electron
Negative
Outside of Nucleus – occupying energy levels

3. Atoms
Atoms are neutral because same number of positive particle (protons) as negative particles (electrons)

4. Elements and Isotopes
Elements – Pure substance that consists of only one type of atom.
Those things listed on the periodic table of elements
Element
Not an element
Helium
Water

6. C An Element in the Periodic Table 6 Carbon 12.011 Atomic Number –
Number of protons
(number of electrons)
Carbon
12.011
Average atomic mass –
Average of all isotopes
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7. Simple Equations
#P = #E
AN = #P
#P + #N = MN

8. Figure 2-2 Isotopes of Carbon
has mass of 14
Nonradioactive carbon-12
Nonradioactive carbon-13
Radioactive carbon-14
Decaying atom becomes
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
6 electrons
6 protons
8 neutrons
90% of all carbon
Has mass of 12
Radioactivity – lose neutrons
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9. Elements and Isotopes Isotopes
Atom that differs in number of neutrons they contain
Identified by their various mass numbers
Electron number determines chemical property and isotopes of the same element still have same number of electrons

10. Radioactivity – lose neutrons
Figure 2-2 Isotopes of Carbon
Section 2-1
10% of carbon
has mass of 14
Nonradioactive carbon-12
Nonradioactive carbon-13
Radioactive carbon-14
Decaying atom becomes
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
6 electrons
6 protons
8 neutrons
90% of all carbon
Has mass of 12
Radioactivity – lose neutrons
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11. ELEMENTS and ISOTOPES How are radioactive isotopes useful?
Used to date material based on the given rate at which isotope decays.
Carbon dating

12. Half Life – Amount of time it takes for half of C14 to decay

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17. ELEMENTS and ISOTOPES
Decaying isotopes – decay at a constant and predictable rate!!!
100 50 25
12.5
Same amount of time to lose half

18. Chemical Compounds Chemical Compound
Substance formed by chemical combination (chemically bonded) of two or more elements
Examples: Salt (NaCl), Water (H20), Glucose (C6H12O6)
Two hydrogen atoms for every one oxygen
Chemical Formula indicates that one
sodium atom for every one chlorine atom

19. Chemical Bonds Covalent Bond Ionic Bond
Form to make each atom “happy” = full outer electron shell (8 or 2)
hold atoms in a compounds together
two types
Electrons are shared between atoms
so that both have full outer shell
Covalent Bond
One or more electrons are transferred
from one atom to another so that each
can have full outer shell
Ionic Bond

20. Chemical Bonds Sodium ion (Na+) Chloride ion (Cl-) Transfer
Figure 2-3 Ionic Bonding
Section 2-1
Chemical Bonds
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Transfer
of electron
Protons +11
Electrons -11
Charge
Protons +17
Electrons -17
Charge
Protons +11
Electrons -10
Charge
Protons +17
Electrons -18
Charge

21. Transfer of electron Figure 2-3 Ionic Bonding Sodium atom (Na)
Section 2-1
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Transfer
of electron
Protons +11
Electrons -11
Charge
Protons +17
Electrons -17
Charge
Protons +11
Electrons -10
Charge
Protons +17
Electrons -18
Charge
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22. Chemical Bonds Covalent Bonds
electrons are shared between atoms so that each is stable (full outer shell)
results in a Molecule

23. Chemical Bonds Carbon atom = 4 electrons in outer shell
Carbon wants 8
Hydrogen atom = 1 atom in outer shell
hydrogen wants two

24. Chemical Bonds Notice: by sharing electrons carbon has 8 electrons and
hydrogen has 2 = Happy!