Download Building Atoms! - Biology with Radjewski

Building Atoms!
AP Biology
On your paper
• Label Notes 2.1
Categories
• Cheerios – Electrons
• Smarties – Protons
• Starbursts - neutrons
Build a Helium Atom
Suppose…. What is it called now?
• The number of protons change?
• The number of electrons change?
• The number of neutrons change?
• What is a radioisotope?
Build Hydrogen
Predict in your notebook…
• If Hydrogen gained a proton, what would it be
called….
• If hydrogen lost an electron, what would it be
called…
• If hydrogen gained a neutron?
How many electrons fit each orbital?
• First – 2
• Second -8
• Third -8
Build Nitrogen
• Is nitrogen electrically stable?
• What does nitrogen need to be electrically stable?
Build Oxygen
• Is oxygen electrically stable?
• What does oxygen need to be electrically stable?
• Is oxygen more reactive than nitrogen?
Build Fluorine.
• Is Fluorine electrically stable?
• What does Fluorine need to be electrically stable?
• Is fluorine more reactive than nitrogen? Oxygen?
What is electronegativity?
• Electronegativity is a
measure of the tendency of
an atom to attract a
bonding pair of electrons
• What is the trend of
electronegativity on the
periodic table?
• Electronegativity increases
from left to right and
decreases from top to
bottom down a column
• Which elements are the
most stable?
• Which elements are the
most reactive?
PDQ 2.1
1. Atom vs. Element
Atom
• Basic unit of matter
• Composed of protons,
neutrons and electrons
Element
• Pure substance
• Contains only 1 kind of
atom
• Has unique characteristics
that distinguish it from
other elements
• 94 elements in nature
• More than 24 have been
made in laboratories
2. 6 elements common in bio
• SPONCH
– Sulfur – found in certain proteins
– Phosphorus – found in DNA
– Oxygen – required for aerobic organisms
– Nitrogen – found in DNA and protein
– Carbon – basic atom in all organic molecules
– Hydrogen – also in all organic molecules
3. Describe atom structure
• Composed of
– Protons – in nucleus, positive charge
– Neutrons – in nucleus, no charge
– Electrons – in orbitals/electron cloud, negative
charge
• Most atoms are electrically neutral, which
means the number of electrons = number of
protons
3. Continued. Label and define
Electron Cloud
nucleus
Center of an
atom where the
protons and
neutrons are
located.
Neutron
Proton
Electron Cloud – Darker areas show probable location of where electrons
would be.
3. Continued. Label and Define
electron
proton
neutron
Orbital/
Electron
Shell
Paths where electrons travel  have varying distances from nucleus
4. Atomic Mass vs. Atomic Number
Atomic Mass
• Protons + Neutrons
• Example – Oxygen has an
atomic mass of 16. Because
it has 8 protons and 8
neutrons.
• The mass written on
periodic tables refers to the
average atomic mass. You
would round this number to
determine number of
neutrons
Atomic Number
• Equal to the number of
protons
• Unique to each element
• Oxygen is number 8 and
therefore has 8 protons.
5. Atomic mass vs. Atomic Weight
Atomic Mass
• Mass of a single atom or an
individual isotope
Atomic Weight
• Is the average mass of all
naturally occuring isotopes
of an element
• Also called average atomic
mass.
• This is what is on the
periodic table.
6. How to calculate number of
neutrons
• Number of neutrons =
atomic mass (rounded)
– number of protons
•
•
•
•
For example, nitrogen.
Protons = 7
Atomic mass is 14.
Number of neutrons =
14-7 = 7.
7. Isotopes
• Have a different number of neutrons than it’s
element
• Each isotope has a different mass number.
• Radioactive isotopes are radioactive and have
an unstable nucleus. (They have excess nuclear
energy)
8. What determines interactions
between atoms?
• Number of electrons
8. Continued… Valence electrons
• Valence electrons are the electrons that are
on the outermost electron shell.
• They determine how reactive the atom will
be.
8. Continued…
One
covalent
bond.
Carbon – 4
Nitrogen – 3
Oxygen - 2
Phosphorus
–3
Sulfur - 2
All atoms thrive to have 8
electrons in their outer shell –
octet rule. They will react to get
it!
Some want it more than
others…..