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