Transcript Chapter 3 Chemical Foundations

Chemical
Foundations Notes
Formulas of Compounds
1. Symbols a.
b.
used to represent the element
first letter is capital, second letter (if necessary) is lower case
C = carbon
2. Subscripts –
a.
b.
Ca = calcium
small number to the lower right of the element symbol
represents the relative composition of each element in a compound
or molecule
CO2 = 1 carbon, 2 oxygen
3. Superscripts –
a.
b.
Cr = chromium
Ba(NO3)2 = 1 barium,
2 nitrogen, 6 oxygen
small number to the upper right of the symbol/formula
used to represent the charge of an ion
Ca+2
Br-1
NO3-1
4. Coefficients –
a.
b.
big number in front of the formula
indicates the number of compounds present
3 CO2 = 3 carbon dioxide or 3 carbon, 6 oxygen
Modern Concept of the Atom
The atom is made of three elementary particles.
Protons
positive charge
1. ____________
2. mass is almost equal to the mass of the
neutrons
___________
nucleus
3. Found in the _____________
4. Number of protons is __________
equal to the
atomic number
Neutrons
no or neutral charge
1. ____________
2. mass is __________________________
than
slightly greater
the proton
nucleus
3. Found in the _____________
4. Neutrons act as the glue that holds together
the nucleus.
- too few or too many neutrons can result
in nuclear instability and then radioactivity
Electrons
negative charge
1. ____________
2. mass is ___________________
2000 x less
than the proton
3. Found moving around the nucleus
at near the speed of light.
- sometimes called
_______________________
or
charge cloud
electron cloud
______________________
4. The Quantum Mechanical Model
- currently accepted model of the
atom (Chapter 11)
- for now we will use the Bohr
model, rings of electrons
neutral
Atoms are always _____________
► Isotopes
same
 Atoms with the __________
number of protons but
different
a ______________
number of neutrons
►


A different number of neutrons results in a different
mass.
Mass of individual atoms is determined by only the
protons and neutrons, the electrons are too light to
be significant.
protons + ___________
neutrons
Mass Number = __________
►

Isotope notations
►
►
40K
means that potassium has a mass number of 40
Potassium-40 also means a mass number of 40
A
Z
X
X = Element symbol
Z = Atomic number = # of protons in nucleus = # on periodic table
A = Mass number = # of protons + # of neutrons in nucleus
Element Symbo Atomic
l
Number
Carbon
Chlorine
Sodium
14C
6
35Cl
17
23Na
11
Mass
Number
Number
of
Protons
Number
of
Neutrons
Number
of
Electrons
6
14
6
8
6
17
35
23
17
11
18
17
12
11
11
Ions
Electron
When an atom gains or loses an __________________
it takes on a charge
and becomes an ion
the charge is determined by the #e- (negative charge) when compared to
#p+ (positive charge)
Calcium ions (Ca+2) has 20 p+ and 18 e- because the calcium atom lost 2
electrons
Fluoride ions (F-1) has 9 p+ and 10 e- because the fluorine atom gained one
electron
Positive Ions are called _______________
Cations
Negative Ions are called _______________
Anions
Element
Symbol
Number
Atomic
Mass
of
Number Number
Protons
Carbon
Chlorine
Sodium
14C+4
6
35
17
23
11
Cl-1
Na+1
6
17
11
14
35
23
6
17
11
Number
of
Neutrons
Number
of
Electrons
8
18
2
18
12
10