Download Atomic Mass

2.1 Nature of Matter
Atom – atomos – “unable to cut”
- basic unit of matter which consists
of 3 SUBatomic particle.
Proton
• Location: in the nucleus (center)
• Mass: 1 amu (atomic mass unit)
• Charge: Positive (+1)
Neutrons
• Location: in the nucleus
• Mass: 1 amu
• Charge: no charge (neutral)
Electrons
• Location: outside of nucleus in orbitals
(electron clouds, energy levels)
• Mass: nearly 0 amu
• Charge: Negative (-1)
Element
• Def – a pure substance that consists entirely
of one type of atom.
• Ex – Gold Rutherford's Experiment:
Nuclear Atom
Chemical Symbols
6
C
12.011
Atomic
Mass
Atomic
Number
1 – 2 letter
chemical
symbol
Atomic Number – the
number of protons found
in the atom
Atomic Mass – the
total number of
neutrons and protons in
the atom. (Units: amu)
Try These
30
11
Na
Zn
23
65.5
How many protons?
11
How many protons? 30
How many neutrons?
12
How many neutrons? 35 - 36
Element Name?
Sodium
Element Name? Zinc
Isotopes
Def: atoms of an element that have different number
of neutrons
• All isotopes have the same chemical properties
Radioactive Isotopes
• Def: isotopes that have unstable nuclei that
become stable by releasing radiation
– Uses of Radioactive Isotopes
• Determine the age of rocks because the
nuclei break down at a constant rate.
• Treat Cancer
Compounds
Def: a substance formed by the chemical
combination of two or more elements in
definite proportions
NaCl - Salt
H2O - Water
C6H12O6 - Glucose
Forming Chemical Compounds
Ionic Bonds – a bond formed when electrons
are transferred from one atom to another.
– Ions: atoms of the same element that have lost
or gained an electron.
– 2-8-8(18) Rule: Elements want to fill their
outer shell by gaining or losing electrons.
Valence Electrons
Valence Electrons: Electrons in the outermost
shell of an atom.
Ionic Bonding
Covalent Bonds
Def: A chemical bond that forms when
electrons are shared between atoms.
Think about Hydrogen
Molecule: the
smallest unit of most
compounds.
Animation
Covalent Bonds
Why does Carbon usually form covalent bonds, instead of ionic bonds?
Answer – Outer shell is half full.
Van der Waals Forces
• Sometimes in covalent bonds the sharing of
electrons is not always equal.
• Slight attraction between slightly charged
regions of a nearby molecules.
• A combination of ionic and covalent bonds
TED - Gecko Talk
Exit Slip
• Draw two molecules of water attached to
each other, show hydrogen bonds, atoms,
and charges.
• Boron is atomic #5 and atomic mass is 11
draw this atom, show all subatomic
particles.
• How many electrons and protons are in
Cu 2+ (ion of copper) Atm. #=29
Exit Slip 9/27
• List at least three unique properties of
water.
• Why would we consider protons to be an
atoms identity and electrons to be like the
personality of an atom?
• Can you explain why one side of a water
molecule is slightly positive and the other
side is slightly negative?