2. Chemistry Notes
Atom
1)_____ : basic unit
of matter
a) nm
Roughly 0.2 ___
in diameter
b) Composed of:
protons (+),
neutrons ( 0 ),
electrons ( - )
3. Chemistry Notes
c) Protons and neutrons are found in
nucleus
the ______ of the atom
i. The number of protons (and electrons)
in an atom is determined by the
atomic
________ number.
ii. The number of neutrons is determined
by subtracting the ___________ from
Atomic number
the ___________.
Atomic mass
Atomic mass – atomic number = neutron #
4. Chemistry Notes
a.Why do we subtract?
An atom’s mass is made up of only
protons and neutrons because the
mass of an electron is negligible
(1/1840 mass of a proton)
5. Chemistry Notes
Atomic mass Atomic number
Element Symbol
Element Name
6. Chemistry Notes
d) orbit
Electrons _________ around the
nucleus in energy levels, or
____________
Shells
i. These shells represent the most
probable place that an electron can
be found at any one time.
ii. Each shell holds a different
number
_________ of electrons.
8. Chemistry Notes
iv. To properly place an atom’s electrons
in the orbitals, follow these guidelines:
1) Start with the innermost orbital and
draw two electrons
2) If you have electrons left, move to
the next orbital and draw up to eight
electrons; continue filling up the
orbital until you run out of electrons.
10. v. This * orbital actually holds more than
what is listed. You will learn more
about this in Chemistry!
vi. The electrons in the outermost shell of
an atom are so important that they
valence
have a special name -__________
electrons
13. Chemistry Notes
2)Element: pure substance made of
one
______ type of atom
a. Grain of Sand (Atom) vs. Beach (Element)
b. Periodic Table of Elements
c. Six most important elements for living things:
C,H,O,N,P,S
14. Chemistry Notes
3) Isotope: ______ element,
same
different number of ________.
neutrons
16. Chemistry Notes
b) properties
Same chemical _____________ due
electrons
to same number of _____________.
c) Radioactive isotopes: nuclei
unstable
__________ and breaks down at a
constant rate.
17. Chemistry Notes
Carbon-14 Dating
d) ____________________ can be
used to determine the age of
biological artifacts up to 50,000
years old by the ratio of radioactive
carbon-14 to nonradioactive
carbon-12 in the artifact.
19. Chemistry Notes
4) Compound: Two or more
definite
elements in ________
proportions.
a) formula
Has a chemical ________.
ex. H2O, NaCl, C6H12O6
b) Compounds are different than the
elements that make them up
20. Chemistry Notes
i. Ex: Sodium (Na) explodes in
cold water, chlorine (Cl) is a
poisonous gas. NaCl is ______.
salt
+ =
21. Chemistry Notes
ii. Oxygen (O2) and Hydrogen (H2)
individually are gases, but together
they are a liquid (H2O)!!
+ =
22. Chemistry Notes
5) Chemical Bonds Hold atoms in
_____________:
compounds together
a) Ionic Bond: Forms when valence
electron (s) move from one atom to
_____
another atom.
i. Ionic bonds occur between metals
nonmetals
and ____________.
23. Chemistry Notes
ii. Why do electrons what to move in
the first place?
1) stable
Atoms want to be _______ by having a
full
______ outer ring. Most are NOT
stable by themselves.
This oxygen atom is NOT
stable.
24. Chemistry Notes
2) To become stable, an atom reacts
with other atoms by giving up or
gaining electrons in order to end up
eight
with _______ valence electrons
Two
(_____ for the first orbital), This is
octet
called the_______ rule.
25. Chemistry Notes
iii. An atom that has gained or
lost electrons is called an
ion
_________.
(1)Atoms that give up electrons
become __________
positively
charged.
(2)Atoms that gain electrons
become __________
negatively
charged.
27. Chemistry Notes
iv. Some atoms already have a full
outer orbital by themselves.
a) Which of the atoms that you drew
earlier fits this description?
_________ argon
b) These atoms are known as the
_____________
noble gases (Group 18)
29. Chemistry Notes
b) Covalent Bonds: _______ electrons
Shared
between atoms
i. Moving electrons spend time between
______ atoms
both
ii. Occurs between nonmetals and
nonmetals
_________.
iii. Atoms achieve their full outer shell
status by sharing electrons
30. Covalent Bonds
iv. Electron sharing combinations
single
1) Two electrons shared = ______
bond
2) Four electrons shared = double
bond
Six
3) _______ electrons shared = triple
bond
31. Chemistry Notes
v. Molecules
__________ form when atoms join
covalently
Use your brain power: Decide which
picture accurately depicts the relationship
between compounds and molecules
34. Chemistry Notes
6) Van der Waals Forces: When
the sharing of electrons is
______ and a molecule has
unequal
regions that are charged.
a) Weaker than ionic or covalent
bonds
b) Geckos stay on walls because of
these forces
