Characteristics of Life, Cell Theory, and Atomic Structure

Classified in Chemistry

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Three major characteristics of life

1.Energy 2.Cells 3.Information
4.Replication 5.Evolution

The cell theory

All organisms are made of cells and come from pre-existing cells

Three major domains of life

Archaea, Bacteria-Prokaryotic microorganism, single-celled whose cells have no nucleus


A trait that increases the fitness of an individual in a particular environment
Genus-Made up of a closely related group of species
Species-made up of individuals who regularly breed together

Atoms are composed of


Atomic number-atoms with the same atomic number, have the same chemical properties, belong to the same element(Is on bottom and represents the number of protons)

Mass Number-

number of protons plus neutrons of the most common isotope(Is on top)

Electrons move around orbitals, each orbital holds 2 electrons, orbitals are grouped into levels called electron shells, Electrons shells are numbered, the smaller the number the closer it is to the nucleus. each electrons shell contains a specific number of orbitals. electrons fill the inner shells first then the outer. outside shell has to have 8 electrons and is called valance shell

Atoms-Are most stable when each electron orbital is filled
Molecules-Are substances held together by covalent bonds
Covalent Bond-Each atoms unpaired valence electrons are shared by both nuclei to fill their orbitals.
Ionic Bond-Electrons are transferred from one atom to another


An atom with a molecule with a high electronegativity, holds electrons more tightly, has a negative charge,the other atom will have a positive charge
NonPolar Covalent bond-Electrons are evenly shared,Bond is symmetrical
Polar covalent bond-Electrons are asymmetrically shared


An atom or molecule that carries a charge
Cation-Atom that loses an electron and becomes positive charged
Anion-Atom that gains electron and becomes negative charged

Ionic bond-

resulting in attraction between oppositely charged ions.

Life is based on water because it is a GREAT SOLVENT, covalent bonds in water are polar because oxygen has a greater electronegativity than hydrogen. Oxygen has a negative charge, Hydrogen has a positive charge.
Water-is unique due to its structure, small size, Bent shape, highly polar covalent bonds, overall polarity

PH scale- The more hydrogen you have the more acidic and the less basic
Potential Energy-is stored energy. bonds contain this and release kinetic energy when bonds break

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