Elements, Atoms, and Ions
Elements
88 occur naturally
Table 4.1 -18 most abundant elements
in Earth’s crust, oceans, and
atmosphere
Table 4.2 - Abundance of elements in
the human body
Symbols
-one, two, or three letters
-first letter is capitalized, others are
not
-some come from English names
-some come from Latin names
Dalton’s atomic theory
1.
2.
3.
Elements are made of tiny particles
called atoms.
All atoms of a given element are
identical.
The atoms of a given element are
different from those of any other
element.
4. Atoms of one element can combine with
atoms of other elements to form
compounds. A given compound always has
the same relative numbers and types of
atoms.
5. Atoms are indivisible in chemical
processes. Atoms are not created or
destroyed in chemical reactions. Atoms
are simply rearranged.
Formulas of compounds
Compound - distinct substance that is
composed of the atoms of two or
more elements and always contains
exactly the same relative masses of
those elements.
Chemical formula
-atoms are indicated by element symbols
-number of each type of atom is indicated
by a subscript
*if there is no number after the
chemical symbol, there is only one atom of
that element
Atomic Structure
J.J. Thomson - atoms contained negative
particles, which are now called electrons
Rutherford - atoms have a dense center of
positive charge
*proton - positive charge in nucleus
*neutron - neutral particle in nucleus
Atoms differ in:
number of protons
number and arrangement of electrons
- electrons determine the chemical
behavior of atoms
Isotopes
Atoms with the same number of protons but
different numbers of neutrons
Atomic number - # protons
Mass number - # of protons and neutrons
- X = symbol of element
- A = mass number
- Z = atomic number
A - Z = number of neutrons
Natural states of elements
Noble elements - gold, silver, platinum
relatively unreactive
Diatomic molecules - molecules made up
of two atoms
HON F ClIBr
Ions
Atoms are neutral - zero net charge
Ions are atoms with a charge
*cation - positive ion, produced when
electrons are lost
*anion - negative ion, produced when
electrons are gained
Ion charge can be predicted
using the periodic table
Group 1 ----1+ (lose one electron)
Group 2 ----2+ (lose two electrons)
Group 13 ----3+ (lose three electrons)
Group 14 ----4+ (lose four electrons)
Group 15 ----3- (gain three electrons)
Group 16 ----2- (gain two electrons)
Group 17 ----1- (gain one electron)
Group 18 ---- no charge
Compounds that contain ions
Ionic compounds:
*Often have very high melting points, and
conduct electric current when melted or
dissolved in water.
*Composed of a metal (cation) and a
nonmetal (anion)
*Have a net charge of zero (positive
charge = negative charge)