PERIODIC TABLE
Chemistry Part 2
Chemistry
A knowledge of chemistry is essential for understanding the structure and function of animals because body functions involve chemical reactions.
Matter
Matter – is anything that occupies space and has mass.
Elements
Elements – Pure substances that cannot be broken down into simpler units.
Atoms
Atoms –are composed of a nucleus and an electron cloud.
Nucleus – central core of an atom and is made up of Protons (particle with a positive charge) and Neutron – (particle without a charge, it’s neutral)
Atoms
Electron cloud – electrons around the nucleus
Electrons – particle with a negative charge
Periodic Table Atomic number = number of protons Atomic Mass=
Total numbers Of protons plusNeutrons in Nucleus.
Isotopes
Same atoms; different numbers of neutrons, therefore different atomic mass.
Examples: Carbon 12 and Carbon 14Carbon Atomic Number 6, so how many
neutrons in Carbon 12?6Carbon 14?8
Radioisotopes
Unstable IsotopesUnstable nuclei, which tend to undergo
radioactive decay.Carbon 14 is unstable isotope. (half-life of
5,730 years)Carbon 12 is stable.
Electrons
Energy levels – different locations of electrons around the nucleus
First level – 2 electrons
Second & all other levels – 8 electrons
Electrons
The amount of electrons in the outermost energy level leads to properties of the atom – will it react with other atoms?
Valence Electrons
Number of electrons in outermost shell.If the outer shell is full then NO REACTION!Column 8, valence shell has 8 electrons, it is
full, NO REACTION!!Columns 1-7?Fill in info on periodic table.
Electron Dot DiagramIllustrates energy
levels and the number of electrons in all shells.
Can put symbol in center to represent nucleus.
Easy way to determine number of valence electrons.
Lewis Dot Structure
Write symbol for element.Indicate valence electrons by putting dots
representing electrons found in OUTER SHELL ONLY. (only show electrons that are available for bonding)
Ex:
uc
Covalent Bonds
Atoms SHARE electrons.Use Lewis Dot Structures
Ionic Bonds
Electrons TRANSFER of electrons.Use Lewis Dot Structure
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