Transcript The Chemistry of Living Cells

The Chemistry of Living Cells
What are ATOMS?
•Atoms are the basic building
blocks of matter that make up
everyday objects. A desk, the
air, even you are made up of
atoms!
•There are 90 naturally occurring
kinds of atoms. Scientists in labs
have been able to make about 25
more.
Everything is composed of
ATOMS!
Atoms are made of?
• Three basic particles:
– Electrons-carry a negative charge, are outside
nucleus (in a neutral atom, same # as # of protons)
– Protons-carry a positive charge, are inside nucleus
(in a neutral atom, same # as # of electrons)
– Neutrons-carry NO charge, are inside nucleus
– Ions = atoms (or molecules)
with missing or extra electrons,
giving it an electrical charge
(+ or -)
Draw this diagram and label the parts:
Atoms Contain Energy!
• It takes energy to prevent the (-) electrons from
crashing into the (+) protons. WHY?
• Electrons are
organized in an
electron cloud in
different energy
levels.
• The farther away
from the nucleus the
energy levels is, the
higher the energy.
The electron cloud shows the most
probable location of the electrons.
More to come in Chemistry!!!
Energy Levels
This will get more
complicated in chemistry!!!)
• VALENCE ELECTRONS
– The electrons in the outermost energy level.
– The maximum number is 8. These are the electrons
involved in chemical bonding.
• The energy level can have less than the maximum
but then it is UNSTABLE/UNHAPPY.
• The atom will GAIN or LOSE electrons to
become stable add: (OR IT MAY SHARE!!!!)
Periodic Table
Represents atoms that make up elements
Elements
• ELEMENTS: Pure substances that consist
entirely of one type of atom; Cannot be
broken down into simpler substances
• Elements related to living things:
How to read an element on the periodic table?
Atomic # = # of protons and #electrons
Atomic mass = # of protons PLUS # neutrons
Protons = atomic #
Electrons = same as protons/atomic #
Neutrons = atomic mass – atomic #
Practice!!
• Hydrogen
• Carbon
Answers!
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Hydrogen
Atomic # = 1
Atomic mass = 1
Protons = 1
Electrons = 1
Neutrons = 0
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Carbon
Atomic # = 6
Atomic mass = 12
Protons = 6
Electrons = 6
Neutrons = 6
Extension: Draw these atoms above the chart!!!
Bonds and Compounds
• COMPOUND = a group of atoms held together
by chemical bonds. Example: NaCl, H2O
Chemical Formulas for Compounds
• CHEMICAL FORMULA: Shows the
number of each element in the compound
 Each capital letter is a new element
• Subscript: (# below the symbol) tells how
many atoms of that element there are
– If there is not a subscript, it is considered ONE
atom
• Coefficient: # in front of the chemical
formula, tells how many of that compound
there are
Examples:
C6H12O6
2C6H12O6
Types of Bonds
• Covalent
• Ionic
• Hydrogen
COVALENT BONDS = Occur when two atoms share a pair of
electrons; called molecules, not compounds
MOLECULE = a group of atoms held together by covalent bonds.
Example = Water
IONIC BONDS = when one or more electrons
are transferred from one atom to another
(one loses electron(s), one gains electron(s)
*Sodium loses an electron-becomes a positive cation.
*Chlorine gains an electron; becomes a negative anion.
The attraction between the cation and anion makes the ionic
bond.
• HYDROGEN BOND = a
weak chemical bond that
forms between 2 polar
molecules.
• POLAR MOLECULES =
unequal areas of charge.
• Water molecules have a slight
(+) charge at the hydrogen and
slight (-) charge at the oxygen
that causes them to attract
forming hydrogen bonds.
Summary of chemical bonds
• Covalent: weak (melting sugar)
• Ionic: strong (hard to melt salt)
• Hydrogen bonds: weakest
(individually), but strong collectively.