Download Helpful PPT on Atoms and Bonding

Basic chemistry
Why learn it?
Life depends on chemistry. If the first task of
an architect is to understand building
materials, then the first job of a biologist is to
understand the chemistry of life.
Where?
Chapter 2 of your textbook
What?
In order:
1. The basics: Atoms and Compounds (small)
2. Properties of Water
3. Macromolecules (big)
4. Enzymes: how they get things done
I anticipate a number of lab activities, at least
1 project, and 1 vocab assignment. There will
also be some small homework assignments.
Atoms
• Atoms – The basic unit of matter.
Atoms are very small, made up of
subatomic particles that are even
smaller than the atom. Atoms are
usually neutral, meaning they have no
charge.
Protons
• Protons  Have about the same mass as a neutron.
  Have a positive charge
  Contained in nucleus in the center of the atom
• Atoms have the same number of protons as electrons
Neutrons
• Neutrons
  Have about the same mass as a proton.
  Have no charge = neutral
• Contained in nucleus in the center of the
atom
Electrons
• Electrons
  Negatively charged particle
  Electrons are in constant motion
  They move around the out side of the nucleus
  Atoms have the same number of protons as
electrons
  Electrons are in orbits around the nucleus
  The first orbit can hold 2 electrons
• The second orbit can hold up to eight electrons
Element
• Element  is a substance composed of only one
type of atom
  more than 100 elements
  Elements are represented by one or two
letter symbol
• Sum of protons and neutrons in nucleus is
called atomic mass
Periodic Table
• Atomic Number - Simply refers to the
number of protons present in the atom.
• Element Symbol - This is the symbol that
chemical formulas or equations use to
indicate that certain element.
• Atomic Mass - The average mass of one
atom of that element in amu's (Atomic Mass
Units).
Compounds
Chemical compounds

Substance formed by two or more elements

Formed in definite proportions

Properties of compound is different that the
elements its formed by

Hydrogen and oxygen are gases at room
temperature, when combined they form water, a
liquid, at room temperature.
Bonding
Chemical Bonds  Atoms in a compound are held together
by chemical bonds
  Bonds are formed by the electrons in
the area around the nucleus
• The electrons that are available to from
bonds are called valence electrons
Bonding
Covalent bonds
  Strongest bonds
  Shared electrons
Single covalent Bond
•Two electrons are shared

Double covalent bond
•Four electrons are shared
Ions
• Ions
  Ions are formed by giving up or
receiving an electron
  Ions can have a positive charge or
negative charge
  If atom gives an electron it has a
positive charge called a Cation
• If atom gains an electron it has an negative
charge called an Anion
Ionic Bonds
Formed when one or more electrons
are transferred from one atom to the
other

Isotopes
• Isotopes  Have different number of
neutrons
  They have the same
number of electrons & protons
• All chemical properties such as bonding
remain the same
Van der Waals
Forces
• Van der Waals Forces
  Not all electrons are shared equally when
bonds are formed
  When sharing is unequal, one end of a
molecule may be slightly more positive or
negative than the other
  A slight attraction between molecules can
develop because of oppositely charged regions
Van der Waals forces