Biology – Unit 3. Put the following words in order from smallest to largest: ◦ Cell, atom,...
-
Upload
shanon-sims -
Category
Documents
-
view
218 -
download
1
Transcript of Biology – Unit 3. Put the following words in order from smallest to largest: ◦ Cell, atom,...
The Chemistry of LifeBiology – Unit 3
Put the following words in order from smallest to largest:◦ Cell, atom, organelle, subatomic particle,
molecule, tissues, organism, organ, macromolecule, organ system
The Complexity of Life
Basic unit of matter Atoms are EXTREMELY small
◦ If placed side by side, 100 million atoms would make a row only 1 cm long!
◦ http://learn.genetics.utah.edu/content/begin/cells/scale/
Atoms are made up of…
Atoms
The three subatomic particles: ◦ Protons◦ Neutrons ◦ Electrons
Subatomic particles
Protons and neutrons have about the same mass.
Protons and neutrons are located in the nucleus of an atom
Protons:◦ Positively charged particles (p+)
Neutrons:◦ Particles that carry no charge◦ “neutral” (no)
Protons and Neutrons
Negatively charged particles (e-) Much smaller than the mass of a proton In constant motion in the space surrounding
the nucleus Atoms have equal numbers of electrons and
protons (negative and positive charges balance out) and atoms are neutral
Electrons
Where have you heard of the term “elements” before in science? Can you think of any examples?
Element: pure substance that consists entirely of one type of atom
Periodic Table of Elements
Elements
Periodic Table of Elements
How many protons does a sodium (Na) atom have?
How many neutrons does a flourine (F) atom have?
What is the atomic mass for oxygen (O)? What is the atomic number for phosphorus
(P)?
Practice Problems
Representing Atoms
Atomic model for Carbon◦ Record how many protons, electrons and neutrons
are present in a carbon atom using periodic table◦ Draw the atomic model for carbon◦ Practice with atomic models and beads
Practice
Using your notes and a periodic table, work with a partner to model then sketch each atom in your lab notebook.
For each atom record:◦ Name of element AND symbol◦ # electrons◦ # protons◦ # neutrons
Build and draw the following atoms:◦ C, H, N, P, O, S
Modeling Atoms Lab
Look at the outer orbital of each atom that you made a model of. How do you think the number of electrons on the outer energy level (valence shell) relates to how stable the element is?
Answer: ◦ Elements with full outer orbitals (valence shells)
are more stable and less reactive◦ Elements with partially complete valence shells
are more reactive
Questions
Based on what you know about certain elements and their Bohr model, find an element that would have a full valence shell (stable)
Questions
Fill in each statement
◦ A change in the number of protons =
◦ A change in the number of neutrons =
Questions
Atoms of an element that have different numbers of neutrons.
Total number of protons and neutrons is the mass number (#protons + # neutrons = mass number)
Isotopes
Isotope # protons # electrons # neutrons
Carbon – 12Nonradioactive
6 6 6
Carbon – 13Nonradioactive
6 6 7
Carbon – 14Radioactive
6 6 8
Radioactive elements have unstable nuclei ◦ When nuclei are unstable they break down at
constant rate over time Used in determining age of rocks and fossils Used to detect and treat cancer Used as a “tracer” to follow movement of
substances within organisms.
Radioactive Isotopes
Chemical compound-◦ Substance formed by the chemical combination of
two or more elements in definite proportions.◦ Written in chemical formulas
Examples:◦ H2O: 2 hydrogens : 1 oxygen◦ NaCl 1 sodium : 1 chlorine◦ NaOH 1 sodium : 1 oxygen : 1 hydrogen◦ CO2 1 carbon : 2 oxygens
Chemical Compounds
H20 vs. H2O2
When the ratio of elements in a compound changes, the physical and chemical
properties change as well.
Chemical Compounds
Atoms are held together by chemical bonds 2 main types:
◦ Ionic bonds◦ Covalent bonds
Chemical Bonding
Model and draw a sodium (Na) and a chlorine (Cl) atom
How many valence electrons are in the outer shells of each atom?
Which atom could easily lose an electron? Explain
Which atom could easily gain an electron? Explain
Lab Activity
Formed when one or more electrons are transferred from one atom to another
Atoms lose or gain electrons◦ Lose electrons becomes positively charged
(+)◦ Gain electrons becomes negatively charged
(-) Atoms that have gained or have lost
electrons are ions
Ionic Bonds
Ionic Bonds
Model and draw the ionic bond between the sodium and chlorine ions, then draw below.
Lab Activity Continued
Methane, CH4, is a molecule that is made up of one carbon atom and four hydrogen atoms.
What do you notice about the outer shell (valence shell) of each of these atoms?
Lab Activity Continued
Electrons are shared between atoms The structure that is formed when two or
more atoms are joined by covalent bonds is a molecule
Covalent Bonds
In order to form the CH4 molecule, the atoms covalently bond to each other. Draw the CH4 molecule on your paper.
Lab Activity Continued
How do the valence electrons influence molecular bonding?
Answer:◦ Number of open placed on the valence shell
determines the number of bonds the atom can make
Questions
Carbon dioxide, CO2, is a molecule that is made up of one carbon atom and two oxygen atoms.
What do you notice about the outer shell (valence shell) of each of these atoms?
Lab Activity Continued
In order to form the CO2 molecule, the atoms covalently bond to each other. Draw the CO2 molecule on your paper.
Lab Activity Continued