BIOLOGY 110 Supplemental Resources – Prof Trueba 1 BIOLOGY 110 – Prof. Trueba Worksheets Chemistry of Life Atoms and subatomic particles Atom – smallest unit of matter that has the properties of an element Subatomic particles: Subatomic Particle Location in Atom Charge Relative mass Proton (H + ) Neutron Electron (e - ) Periodic table of elements – Elements organized by number of protons. From upper left to right, from 1 to over 100. Therefore, the periodic table of elements is organized by Atomic Number. Atomic Number = Number of protons = Number of electrons (because atoms are neutral having the same number of positive charges and negative charges - except in ions – discussed later) Atomic Mass = Protons + Neutrons (Round up to the closest whole number) Locate the Atomic Number and Atomic Mass in the periodic table of elements (Fig. 1.1) and complete the following table Element Chemical Symbol Atomic Number Atomic Mass Number of Protons Number of Electrons Number of Neutrons Hydrogen Carbon Oxygen Nitrogen Chloride Sodium
Transcript
BIOLOGY 110 Supplemental Resources – Prof Trueba
1
BIOLOGY 110 – Prof. Trueba
Worksheets
Chemistry of Life
Atoms and subatomic particles
Atom – smallest unit of matter that has the properties of an element
Subatomic particles:
Subatomic Particle Location in Atom Charge Relative mass
Proton (H+)
Neutron
Electron (e-)
Periodic table of elements – Elements organized by number of protons. From upper left to right,
from 1 to over 100. Therefore, the periodic table of elements is organized by Atomic Number.
Atomic Number = Number of protons = Number of electrons (because atoms are neutral having
the same number of positive charges and negative charges - except in ions – discussed later)
Atomic Mass = Protons + Neutrons (Round up to the closest whole number)
Locate the Atomic Number and Atomic Mass in the periodic table of elements (Fig. 1.1) and complete the following table
Element Chemical Symbol
Atomic Number
Atomic Mass
Number of Protons
Number of Electrons
Number of Neutrons
Hydrogen
Carbon
Oxygen
Nitrogen
Chloride
Sodium
BIOLOGY 110 Supplemental Resources – Prof Trueba
2
Isotopes are atoms of the same element that differ in the number of ___________
Isotope examples: C-12 and C-14; Iodine-127 and Iodine-131 (for thyroid cancer treatment)
How many protons, neutrons, and electrons do C-12 and C14 have?
Electron Orbitals – Probable location of e-. Can hold up to two e-.
Electron Orbitals with same Energy Level = Electron or Energy Shell
1st Energy Shell 1 electron orbital Up to 2 e-
2nd Energy Shell 4 electron orbital Up to 8 e-
3rd Energy Shell For this class we only considered 4 electron orbital
Up to 8 e (for this class only)
Draw the structure of the atom indicating the electrons in the energy shells for the following elements: Carbon (6,12) Hydrogen (1,1)
Oxygen (8,16) Sodium (11, 23)
BIOLOGY 110 Supplemental Resources – Prof Trueba
3
Valence shells – are the outermost shell of an atom. It contains the Valence e- which are the
most energetic.
If Valence shell is not full to maximum capability , the atom is NOT stable and considered
Reactive.
Atoms that are reactive will react with other atoms for chemical stability - Atoms will form
chemical bonds with other atoms forming a stable molecule. Atoms will share e-, gain e-, or lose
e- to be chemically stable (valence shells full)
Types of Bonds:
1. Covalent Bond
2. Ionic Bond
3. Hydrogen Bond
1- Covalent Bonds = sharing e- (Strongest Bonds) Draw the structure of two H atoms with e- in shells Are they stable as atoms? _____ If they both share one e-, will the Hydrogen Molecule be stable? ____ Draw the structure of Molecular Hydrogen
Molecule = 2 or more atoms bonding
BIOLOGY 110 Supplemental Resources – Prof Trueba
4
Draw the structure of two O atoms with e- in shells Are they stable as atoms? _____ If they both share 2 e-, will the Molecular Oxygen be stable? ____ Draw the structure of Molecular Oxygen
Draw the structure of one H atom and one F atom with e- in shells Are they both stable as atoms? _____ If they both share 2 e-, will the Molecule HF be stable?____ Draw the structure of Hydrogen Fluoride
BIOLOGY 110 Supplemental Resources – Prof Trueba
5
Fill in the following table:
Covalent Bond Type Number of e- shared Single
Double
Triple
Molecular versus Structural Formula
Molecular formula (formula of the molecule) – i.e.: H2 (Molecular Hydrogen)
Structural formula (structure of the molecule indicating all covalent bonds – i.e.: H-H (the line
between the two Hydrogens represents one single covalent bond, therefore the sharing of __e-
(indicate how many electrons are share per covalent bond)
Draw the Structural Formula give the Molecular Formula
Molecular formula Structural Formula (indicating all C.B.)
H2O
CH4
Calculating the Number of Covalent Bonds Atoms Can Form (= number of e needed to complete Valence shell):
Atom Number of e in Valence shell
Number of e needed to complete Valence Shell
Number of C. B.
Hydrogen
Oxygen
Nitrogen
Carbon
Nitrogen
BIOLOGY 110 Supplemental Resources – Prof Trueba
6
Polar versus Non-Polar Covalent Bonds
Electronegativity of an atom (or e- “greediness”) is the tendency to attract the electrons shared in a bond towards them. How Electronegativity increases in the periodic table of elements
- Non-Polar Covalent Bonds are the result of atoms that share electrons equally. Atoms that
have similar electronegativity will share the electrons equally. Molecules are neutral (same
number of positive charges (protons) as negative charges (electrons). In this case of equal
sharing electrons all the negative charges of electrons are equally distributed around all
atoms that compose the molecule.
i.e.: C and H have similar electronegativity so the e- are shared equally. CH4 is an example of
a molecule with non-polar covalent bonds
- Polar Covalent Bonds are the result of atoms that share electrons unequally. Atoms that
have different electronegativity will share the electrons unequally. Atoms with higher
electronegativity will have a higher pull on the electrons being shared. Molecules are
neutral but in this case, because of the unequal sharing of electrons, the electrons will be
closer to atoms in the molecule with higher electronegativity. This will create Partial
Charges:
o Negative Partial Charge – in the atoms of the molecule with higher electronegativity
o Positive Partial Charge - in the atoms of the molecule with lower electronegativity
What is the most electronegativity element? _______
BIOLOGY 110 Supplemental Resources – Prof Trueba
7
i.e.: O and H have different electronegativity so the e- are shared unequally. H2O is an
example of a molecule with non-polar covalent bonds
Draw the water molecule indicating the partial charges:
To know if the bond is Polar or Nonpolar, we can use the Electronegativity Value of the
Elements (Pauling Scale) table provided at the end (figure 1.2).
o If the difference in electronegativity between the two atoms that share electrons is
less than 0.5, then the covalent bond is Nonpolar.
o If the difference in electronegativity between the two atoms that share electrons is
between 0.5-2.0, then the covalent bond is Polar.
Are the following bonds polar or nonpolar based on their electronegative difference?
Bond between Polar or Nonpolar Bond? O and H
C and H
S and H
C and S
N and H
P and O
S and H
BIOLOGY 110 Supplemental Resources – Prof Trueba
8
2- Ionic Bonds: Attractions between ions, a positively and a negatively charged ions.
Ions: Atoms that are unstable (valence shell not full) and therefore lost or gained electrons
to reach chemical stability.
o Positively Charged Ion (Cation) – atom that ____________ (lost or gained?) e-
o Negatively Charged Ion (Anion) - atom that ____________ (lost or gained?) e-
How to figure out if two atoms will form an Ionic Bond? If the difference in electronegativity is
2 or more, the atoms will ionize (one will gain 1 or more electrons from the other atom).
Positive and negative ions then will be electrostatically attracted forming an ionic bond
Bond Type Electronegativity Difference
Nonpolar Covalent Bond <0.5
Polar Covalent Bond 0.5-2
Ionic Bond 2 or more
Use the Pauling Scale (Fig.1.2), what is the difference in electronegativity between sodium and
chloride? _________
Draw the structure of the atoms:
Sodium Chlorine
Number of Protons (+) Number of electrons (-) Number of Neutrons (0) Net charge
BIOLOGY 110 Supplemental Resources – Prof Trueba
9
Are these atoms neutral? _________
Are the Valence Shell of these atoms full? __________
Are these two atoms stable or are they reactive? ____________
How can these atoms become chemically stable? ___________________________________
