chem 101 lecture 2

Negatively charged subatomic particle that orbits the nucleus of an atom

Positively charged subatomic particle that is located in the nucleus of an atom.

Uncharged subatomic particles that hold protons and electrons together. (protons repell other protons..)

Number of protons in the nucleus (number at top of element square in periodic table.)

Number of protons

A= mass number = number of nucleons = # of protons +neutrons.

• Example:
• Flourine 9p
•              9e
•            10n
• Z=9 A= 19

These are the outer most electrons. they are the most chemically important. this number is the  small number for the groups on the periodic table (1- 8)

can be found by subtracting bottom number from top number in periodic table.

They are stable and will not react with other atoms. They all have 8 valence electrons except for helium which has 2.

• There are no joined molecules. Metal paired with non metal is a good indicator. Example
• NaCl Na+Cl

Unstable atoms react to reach a stable state that has the same number of electrons as the nearest (by atomic number in periodic table) noble gas... valence electrons can be transferred

Results from transfer of electrons between metals (cation) and non metals (anion)

sharing of electrons between non metals

• Usually found as solid
• needs very high temp to become l or g
• many dissolve in water

a charged species (ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit in the context of acid and base chemistry or in the formation of salts.

H₃O⁺

OH^-

NH₄⁺

CH₃COO^-