Download Atoms - Issaquah Connect

Atoms and
Elements
Structure of an Atom
Orbits
Charges
• Electron – negative
• Proton – positive
• Neutron - neutral
Location in Atom
• Electrons – in orbitals
• Protons & Neutrons –
in nucleus
Nucleus
Elements
• Pure chemical substances made up of one type
of atom
• Building blocks
of matter
• Over 115 elements
known - and more
being discovered
Elements – Symbol / Name
Symbol: one
or two letter
abbreviation
Examples:
C
Carbon
O
Oxygen
Mg
Magnesium
Br
Bromine
Au
Pb
K
Na
Latin
Gold-aurum
Lead-plumbum
Potassium-kalium
Sodium-natrium
Elements – Atomic Number
DEFINES the
element
Atoms are neutral…
so have same #
electrons (-) as
protons (+)
• ALL atoms of the same element have the same number
of protons.
• All neutral atoms have no overall (net) charge,
so … have the same number of electrons as protons
• BUT… they can have different numbers of neutrons
These are called isotopes of carbon
Elements – Atomic Mass
“Averaged mass”
Calculated
from Mass
Number
• MASS NUMBER = mass of all particles in
one atom (protons, neutrons and electrons)
• Measured in “atomic mass units” (amu)
Elements – Mass Number
• MASS NUMBER = mass of all particles in one
atom (protons, neutrons and electrons)
• Mass of 1 proton = 1 amu
Mass of 1 neutron = 1 amu
Mass of 1 electron = really, really tiny!
• SO…
mass number = # protons + # neutrons
Carbon - 12
• 6 protons x 1 amu/proton = 6 amu
• 6 neutrons x 1 amu/neutron = 6 amu
• 6 electrons x really tiny mass = 0 amu
TOTAL = 6 amu + 6 amu + 0 amu
= 12 amu
Elements – Mass Number
Helium - 4
Nitrogen - 14
Atomic Number = 2 (protons)
Mass Number =
4 amu (p + n)
Number of Neutrons = 2
Atomic Number =
7 (protons)
Mass Number =
14 amu (p + n)
Number of Neutrons = 7
“Periodic Table Song”
Pause for….
Practice and Review
Isotopes
•
•
•
•
Different versions of the same element
Same number of protons and electrons
Different number of neutrons
SO…. Mass number (# protons + # neutrons)
is different
• Identified by writing mass number after
element name
ex: Carbon-12, Carbon-13
Isotopes…
• Explain why the atomic mass for Lithium
(atomic number 3; with 3 protons) is 6.94 ! !
Lithium-6
- 3 protons, 3 neutrons
- mass number = 6
- 7.5% of all lithium
Lithium-7
- 3 protons, 4 neutrons
- mass number = 7
- 92.5 % of all lithium
NOTE: Mass number is used
to name isotope
Isotopes and Atomic Mass
• Why the atomic mass for Lithium
(atomic number 3; with 3 protons) = 6.94…
• Calculation: Weighted Average (info. only):
– 7.5 % Lithium-6 at 6 amu
– 92.5 % Lithium-7 at 7 amu
• (0.075 x 6 amu) + (0.925 x 7 amu) =
(0.45 amu) + (6.48 amu) = 6.93 amu
Elements – Atomic Mass
• The atomic mass of an element is calculated
by doing a weighted average of the mass
numbers of all naturally existing isotopes.
• If you round the atomic mass
of an element to the nearest
whole number, you get the
mass number of the most
common isotope.
7.0
Elements – Symbol / Name
Same # protons,
different # neutrons
Atomic Mass
• “Average” for all carbon
• Calculated from mass
numbers of isotopes
• On the periodic table
All have same # protons
Mass Number
• Calculated for each
individual isotope
• Used to name the
isotope
• Averaged together to
represent all carbon
Elements - SUMMARY
Structure of an Atom
• Outside the nucleus
electron
– Electron
• Atomic mass
• Charge
nucleus
(containing protons
and neutrons)
0
(-)
Structure of an Atom
• Electrons are arranged
in orbits
– Orbit 1 holds
2 electrons
– Orbit 2 holds
8 electrons
– Orbit 3 holds
8 electrons…
Structure of an Atom
• Nucleus – the center of an atom contains…
– Protons
• Atomic mass
• Charge
1
(+)
– Neutrons
• Atomic mass
• Charge
1
none
Symbols
• Either 1 or 2 letters symbols
– First letter Capital, second lower case
– Some based on Latin name
Example
Latin
C
Carbon
Au Gold-aurum
O
Oxygen
Lb Lead-plumbum
Mg
Magnesium
K
Potassium-kalium
Br
Bromine
Na Sodium-natrium
The Periodic Table
• Elements are arranged by size and chemical
properties.
• Rows
– Period
• Size
• Columns
– Group
• Properties
Properties
• Properties are related to atomics structure.
• The number of electrons in the outer most
orbit (valence electrons) determine how an
atom will behave in chemical reactions.