Download Atoms, Molecules, and Ions

Atoms, Molecules, and Ions
Atomic Theory of Matter
John Dalton – earliest version of the
atomic theory
1. Elements are composed of small particles called
atoms.
2.
Atoms of a given element are identical
3. Law of Conservation of Matter/Energy –
matter/energy cannot be created or destroyed
4.
Two or more elements that combine chemically
form compounds
Atomic Theory of Matter
Element – one kind of atom
Compound – 2 or more elements
chemically bonded. Chemically
different than elements
Mixture – 2 or more substances
together, each maintains its
chemical identity
Discovery of Atomic Structure
Similar charges repel each other
Opposite charges attract each other
A. Radioactivity
Ernest Rutherford – 3 types of radiation
Alpha (α) – positively charged particle
Beta (β) – negatively charged particle
Gamma (γ) – no charge; dangerous
Alpha particle (α) is the core of a helium atom
Nuclear Atom
J.J. Thomson – atoms are a uniform positive
sphere with electrons
embedded in it.
“Plum Pudding Model”
Nuclear Atom
Rutherford – fired alpha particles at gold foil
to study scattering, most went straight
through, some bounced straight back.
Rutherford – the Nuclear Atom
Deduced that:
most of an atom is empty space
center of atom has a positive charge
The nucleus – small and dense
contains the majority of
the mass of an atom
Rutherford Gold Foil Animation
2.3 Modern View of Atomic Structure
Atoms are composed of 3 particles
Proton – positive charge (+)
Neutron – neutral charge
Electron – negative charge (-)
Mass of an atom – all in nucleus
sum of protons and neutrons
Modern Atomic Structure
Size of an Atom – Between 1-5 Angstroms (Ǻ)
Angstrom (Ǻ) = 1 x 10-10 m
Electron Cloud – area around nucleus where
electrons spend most of their time
- makes up most of the size of an atom
- mostly empty space
How many copper atoms (DCu atom = 2.6 Ǻ) fit
across the edge of a penny (19 mm)?
Isotopes, Atomic #, Mass #
Isotopes, atomic #, and mass # - bookkeeping
of subatomic particles
All atoms of an element have the same number
of protons
Isotopes – Atoms of the same element with
differing #’s of neutrons
- affects mass #
Atomic Number (Z) – number of protons
Mass Number (A) – # of protons + neutrons
Examples:
2.4 Periodic Table (developed in 1869)
Your new best friend!!!!
Periodicity – repeating patterns of chemical
and physical properties
Vertical Columns – family or group; similar chemical
behavior
Horizontal Rows – Periods
Metals – Left of staircase; except Hydrogen;
most are _________ at room temp.
Nonmetals – Right of staircase; includes H
most are _______ at room temp.
Metalloids – lie along staircase,behave as
metal and nonmetal
Elements Song
Meet the Elements
2.5 Molecules and Ions
Molecule – Two or more nonmetal atoms
bonded together
7 Diatomic molecules:
Horses Need Oats For Clear Brown Irises
H2
N2
O2
F2
Cl2
Br2
I2
7 Diatomic Molecules
Subscripts – represent the # of atoms of the
element just before it
Ex: H2O
CaSO4
C6H12O6
Mg3(PO4)2
Molecular, Empirical, and Structural
Formulas
Molecular Formula – Actual # of atoms
Example: C6H12O6 , H2O2
Empirical Formula – Relative # of atoms
smallest whole # ratio
usually for ionic compounds
Example: CH2O , HO , NaCl
Formula Types (con’t)
Structural Formula – lines represent bonds;
indicates which atoms are bonded to each other
Ions – form when an atom gains or loses
electrons
Cation – metal atom loses electrons to
form a positive ion
Anion – nonmetal atom gains electrons
to form a negative ion
Metals are losers (shhhhhh!)
Symbol
17O2-
52Cr3+
Protons
38
34
Neutrons
50
45
74
36
54
Electrons
Net
Charge
2+
1-
Polyatomic Ions
Polyatomic Ions – many atoms with a charge
See test packet for a list of common PAI’s
Covalently bonded (nonmetals)
Predicting Ionic Charge
Predicting Ionic Charge - use the staircase
metals – lose electrons, form cations
nonmetals – gain electrons; form anions
Atoms will gain or lose electrons to have the same
number of electrons as the nearest noble gas (for
the main group [A] elements only)
NOBILITY IS STABILITY
Ionic vs. Covalent
Ionic Compounds – electrons are transferred
from the metal (loser) to the nonmetal
Empirical formula shows ratio –
ionic compounds form large
3-D crystals.
Covalent molecule – electrons are shared
between 2 or more nonmetals