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Defining the Atom: Mr. Smith's Section 4 Coggle (Determining an Atom…
Defining the Atom: Mr. Smith's Section 4 Coggle
The Atom
Definition:
The smallest particle of an element that retains its identity in a chemical reaction.
Democritus
Greek Philosopher
Believed that atoms were indivisible and indestructible.
Among the first to suggest existence of atoms.
Dalton's Atomic Theory
Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.
All elements are com posed of tiny indivisible particles called atoms.
Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Most Radii of Atoms fall between 5x10^-11 m and 2x10^-10 m
Atomic Structure
Neutrons (0)
Discovered in 1932
James Chadwick
Neutral Charge
Mass equal to the proton
Electrons (-)
Discovered in 1897
Physicist J. J. Thomson
Negatively Charged
Smallest part of the Atom
Protons (+)
Positively Charged
Discovered in 1886
Eugen Goldstein
Large Particle (1840x the mass of electron.)
Number of protons determines the atomic number of an atom.
In the nuclear atom, the protons and neutrons are located in the nucleus.
The electrons are distributed around the nucleus and occupy almost all the volume of the atom.
Determining an Atom
elements are different because then contain different numbers of protons.
Atomic Number:
determined by the number of protons in the nucleus of an atom of that element.
In a neutral atom, the atomic number = the # of protons and # of electrons.
Mass Number
the Total number of protons and neutrons in an atom.
Number of Neutrons = Mass Number - Atomic Number
Isotopes
Atoms with the same number of protons, but different numbers of neutrons.
Examples:
Neon-20
10 protons, 10 Neutrons, 10 Electrons
Neon-21
10 protons, 11 Neutrons, 10 Electrons
Neon-22
10 protons, 12 Neutrons, 10 Electrons
Atomic Mass
Weighted average mass of the atoms in a naturally occurring sample of the element
Periodic Table of Elements
Ordered and arranged by the number of protons in the nucleus, aka. THE ATOMIC NUMBER
Periods
Horizontal Rows
Groups
Vertical Columns
Have similar chemical and physical properties.
