CH 2 THE CHEMISTRY OF LIFE2.1 The Nature of Matter

Atoms

Basic unit of matter May be broken into smaller particles that do NOT

have the properties of the element.

Atoms

Very small- 100 million atoms would make a row only about 1 centimeter long

Consists of protons, neutrons, and electrons.

Atoms Nucleus

Core of atom Protons

Positive charge, in nucleus, mass of 1 atomic unit Neutrons

No charge, in nucleus, mass of 1 atomic unit Electrons

Negative charge, orbits nucleus, mass of 0 atomic units (technically a mass of 1/1840).

Carbon Atom

Atoms have equal numbers of electrons and protons, their positive and negative charges balance out, and atoms themselves are electrically neutral.

Matter is made up of atoms Atoms join together to make compounds Compounds use chemical bonds to hold them

together Chemical bonds are stored energy Molecule

Atoms of the same element joined together.

Elements and Isotopes

Elements and isotopes have same number of electrons

All isotopes of an element have the same chemical properties.

Elements Pure substance that

consists entirely of one type of atom or

Elements cannot be broken down into other types of substances

Mercury (Hg).

Isotopes

Atoms of the same element that differ in the number of neutrons.

Atomic number Number of protons

Atomic Number (atomic mass or weight) Number of protons

and neutrons.

Carbon Atom

Atomic Number 6

Mass Number 12

Radioactive Isotopes

Nuclei are unstable and break down at a constant rate over time

Used for Determine the ages of rocks and fossils by analyzing

the isotopes found in them Detect and treat cancer Kill bacteria that cause food to spoil Labels or “tracers” to follow the movements of

substances within organisms.

Chemical Compounds

Substance formed by the chemical combination of two or more elements in definite proportions

Water, the chemical formula H2O, contains two atoms of hydrogen for each atom of oxygen.

Chemical Compounds

Physical and chemical properties of a compound can be different from the elements that forms it

Sodium Reacts explosively with cold water

Chlorine Very reactive, poisonous, greenish gas that was used in

battles during World War I Sodium Chloride

Table salt.

Chemical Bonds

Attraction between two atoms resulting in a sharing or transferring of an electron(s)

Uses electrons Covalent Bond

Chemical bond that SHARES electrons Ionic Bond

Chemical bond that TRANSFERS electrons Hydrogen Bond

Weak bond between hydrogen ions.

Covalent Bonds Shares electron(s).

Ionic Bond

Transfer of electron(s) Ion

A charged particle Protons do NOT equal electrons

Ionic Bond

A sodium atom easily loses its one valence electron and becomes a sodium ion (Na+).

Ionic Bond

A chlorine atom easily gains an electron (from sodium) and becomes a chloride ion (Cl-).

Van der Waals Forces

Slight attraction can develop between the oppositely charged regions of nearby molecules

Due to unequal sharing of electrons within each molecule

Much weaker than Covalent of Ionic bonds.