BIO 202 Chapter Notes - Chapter 2: Atomic Mass, Trace Element, Periodic Table

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Bio 202 Phemie Chan
Chapter 2
Four different atoms - hydrogen, carbon, nitrogen, oxygen - make up 96% of matter found in
organisms
Matter - anything that has mass is made up of matter
- Elements and atoms - pure substance made up of one kind of atom. Atom cannot be
broken down simpler.
- Molecules and compounds - atoms combined in fixed numbers make molecules and
compounds
Structure of atoms
- protons and neutrons
a. Neutrons - o charge
b. Proton +1 charge
c. Atomic nucleus is positively charged
d. Atoms are electrically neutral
Number of neutrons can vary - leading to isotopes. Isotopes differ in mass and nuclei of some
isotopes are unstable (they decay, or are radioactive)
- Electrons charge of -1, negligible mass
- Attraction between electrons and nucleus preserves the atomic structure
Atomic mass = mass of protons + mass of neutrons
Atomic# = #protons = #neutrons
Number of neutrons can vary atomic forms of same element with different number of
neutrons are isotopes. Isotopes differ in mass and some may be unstable. They breakdown,
decay, releasing energy and matter radioactivity.
Orbitals and shells stable orbital = 2 electrons (one pair) each electron shell consist a specific
table of orbitals
Orbital- a path or place where electrons are, orbiting the atomic nucleus, existing in concentric
circles
First shell 2
Second shell 8
Atoms want to satisfy their orbitals for stability
Periodic table shows electron distribution valence electrons from 1-8
Carbon has four unpaired electrons, that’s why it wants to form covalent bonds so much.
Trace element element needed by an organism only in tiny quantities (less than 0.01%)
Hydrogen, carbon, oxygen and nitrogen are the most abundant elements.
Most abundant elements usually have unpaired electrons which lets it bond with others.
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Document Summary

Four different atoms - hydrogen, carbon, nitrogen, oxygen - make up 96% of matter found in. Matter - anything that has mass is made up of matter. Elements and atoms - pure substance made up of one kind of atom. Molecules and compounds - atoms combined in fixed numbers make molecules and compounds. Protons and neutrons: neutrons - o charge, proton +1 charge, atomic nucleus is positively charged, atoms are electrically neutral. Number of neutrons can vary - leading to isotopes. Isotopes differ in mass and nuclei of some isotopes are unstable (they decay, or are radioactive) Electrons charge of -1, negligible mass. Attraction between electrons and nucleus preserves the atomic structure. Atomic mass = mass of protons + mass of neutrons. Number of neutrons can vary atomic forms of same element with different number of neutrons are isotopes. Isotopes differ in mass and some may be unstable. They breakdown, decay, releasing energy and matter radioactivity.

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