Atoms, Isotopes, and Ions 4.3 – 4.7, 4.10, 4.11. Atomic Theory In 1808 John Dalton proposed atomic...
-
Upload
lester-stanley-allen -
Category
Documents
-
view
217 -
download
0
Transcript of Atoms, Isotopes, and Ions 4.3 – 4.7, 4.10, 4.11. Atomic Theory In 1808 John Dalton proposed atomic...
Atoms, Isotopes, and Ions
4.3 – 4.7, 4.10, 4.11
Atomic Theory
• In 1808 John Dalton proposed atomic theory.
• Dalton’s theory explained several laws known at the time.– Law of conservation of matter– Law of definite proportions– Law of multiple proportions
Dalton’s Atomic Theory (1808)
1. Elements are made of tiny particles called atoms.
2. Atoms of a given element are identical.
3. Atoms of different elements differ from each other in some fundamental way.
Dalton’s Atomic Theory (1808)
4. Atoms of one element can join with atoms of other elements to form compounds.
• A given compound is always made of the same elements combined in the same ways. Explains the law of multiple proportions and the
law of definite composition.
Dalton’s Atomic Theory (1808)
5. Atoms are indivisible in chemical reactions.
• Chemical reactions change how atoms are grouped (bonded) together. Explains the law of conservation of matter.
Atomic Theory
• Dalton’s proposal lead to much research as to the nature of the atom.
• In the late 1800’s chemists/physicists determined that the atom is made up of smaller, subatomic, particles.
Atomic Theory - 1910
• ~1896, JJ Thomson demonstrated that atoms can emit negative particles.– Called these particles electrons.– Since atoms are neutral he also proposed that
they must contain positive particles.• These + particles were not fully described/named
until 1919.
Atomic Theory - 1910
• ~1910 Lord Kelvin proposed the “plum pudding” model of the atom.– Proposed that electrons were scattered within
a “cloud”/pudding of positive charge.
Atomic Theory - 1911
• ~1911 an experiment was conducted in Ernest Rutherford’s lab that showed the “plum pudding” model to be incorrect.– Experiment was conducted by Geiger and
Marsden and the findings interpreted by Rutherford.
– See page 84
The gold foil experiment
• What they did – see board
• What they found – see board
• What Rutherford concluded.
Rutherford’s Model of the Atom
• First to propose a nuclear atom.
• Rutherford proposed that:– the atom must have nearly all its mass, and
positive charge, in a central nucleus about 10,000 times smaller than the atom itself.
– Most of the atom is empty space and the electrons are scattered through out this empty space.
A New Model of the Atom
Expected based on
Plum pudding model
Rutherford’s model
Based on ”his” results
Subatomic Particles
• Rutherford continued to study the atom and the positive matter of the atom.– 1919, + particle named the proton
• ~1932 James Chadwick proposed the existence of a third subatomic particle, the neutron.
Subatomic Particles
Subatomic Particle
Charge Mass, amu Location in atom
Electron
(e-)
-1 0 amu Outside of nucleus
Proton (p) +1 ~1 amu Nucleus
Neutron (n) 0 ~1 amu Nucleus
Mass of Subatomic Particles
• Protons and neutrons have ~ the same mass (in the range of 10 -24 g).
– Neutrons are slightly heavier.– Mass is expressed in amu
• Atomic mass unit (amu) – 1/12 the mass of a carbon-12 atom
Mass of Subatomic Particles
• The mass of the electron is tiny as compared to that of the proton and neutron.– Therefore, the electron’s mass is considered
to be ~0 amu when calculating the mass of an atom.
Subatomic Particles and the Elements
• Each element has a unique number of protons.– Number of protons defines the element.
Subatomic Particles and the Elements
• Since atoms are neutral, for every proton there is a/n _________.
• When atoms interact to form compounds, it is their ___________ that “intermingle”.
Terms
• Atomic number = number of protons in an atom– Also indicates the number of electrons in the
atom.– Finding atomic number on the periodic table.
Terms
• Mass number = sum of the # of protons and the # neutrons in the nucleus of an atom– FOR MOST ELEMENTS THE MASS
NUMBER IF NOT ON THE PERIODIC TABLE.
• You will be given enough information to determine mass number or number of neutrons.
Terms
• Isotopes = atoms of a given element that differ in mass number– Isotopes have the same number of
_____________.– Isotopes differ in the number of _______.
Isotopes
• Writing atomic symbols for isotopes– See board and pg 87
FAQ - Isotopes
• When is mass number found on the periodic table?
• What’s the atomic mass? Is it the same as the mass number?
Practice
• Start # 42 on page 110.
Ion Formation
• Ions are formed when atoms gain or lose electrons.– Proton and neutron number are unchanged
when an ion forms.
Ions - Terms
• Ion – charged atom or group of atoms– Cation = positively charged ion
• Metals form cations.
– Anion = negatively charged ion• Nonmetals form anions.
Ions
• Na atom_____ protons _____ electrons
• Na+ ion _____ protons _____ electrons
Name of ion: sodium ion
Ions
• Calcium atom_____ protons _____ electrons
• Ca 2+ ion _____ protons _____ electrons
Name of ion: calcium ion
Ions
• Sulfur atom_____ protons _____ electrons
• S2- ion _____ protons _____ electrons
Name of ion: sulfide ion
Ion Charge and the Periodic Table
Group # Ion Charge # e- lost/gained
I A 1+ 1 e- lost
II A 2+ 2 e- lost
III A metals 3+ 3 e- lost
V A nonmetals 3- 3 e- gained
VI A nonmetals 2- 2 e- gained
VII A 1- 1 e- gained
Naming Ions
• Name of a monatomic cation is the name of the element– Examples:
• Ca 2+ calcium ion• Al 3+ aluminum ion• K+
Naming Ions
• Monatomic anions are named by changing end of the name of the element to “ide”
Example: S2- sulfide ion
Naming Ions
• You need to know:N3- nitride ionP3- phosphide ionO2- oxide ionS2- sulfide ionF- fluoride ionCl - chloride ionBr- bromide ionI- iodide ion
Ionic Compounds
• Structure– In an ionic compound there is a regular
arrangement of oppositely charged particles. – Ions are arranged in a 3-D crystalline
structure that maximizes attractive forces and minimizes repulsive forces.
• Also called a lattice structure• See page 102
Ionic Compounds
• Physical Properties – all are related to the structure of the compounds– Solids at room temperature– Relatively high melting and boiling points– No vapor pressure
• Meaning… they don’t evaporate
– Electrolytes• Conduct electricity when melted or dissolved in
water
Ionic Compounds
• The chemical formula for an ionic compound represents the lowest, whole number ratio of the component ions that has a net charge of zero.Total positive charge = total negative charge
Ionic Compounds
• Name the compound by naming the ions.
Ionic Compounds
• Writing formulas for and naming binary ionic compounds– Magnesium oxide
Ionic Compounds
Magnesium oxide– The formula is the simplest ratio of ions that
have a net charge of zero.– Ions present: Mg2+ and O2-
– Formula:
Ionic Compounds
Magnesium chloride– The formula is the simplest ratio of ions that
have a net charge of zero.– Ions present: Mg2+ and _____
– Formula:
Ionic Compounds
• Practice– Note we are currently applying the content of
4.11 and 5.2 (type I binary ionic compounds)
Types I Binary Compounds
• Compound between a metal and a nonmetal– Metal forms only one ion
• Name the cation and then the anion.– Name of the cation is the name of the element– Name of the anion is the name of the
nonmetal with the ending changed to “ide”
Monoatomic cations to know
Group # Charge on ion examples
IA +1 Na1+ sodium (ion)
K1+ potassium (ion)
IIA +2 Mg2+ magnesium (ion)
IIIA metals
+3 Al3+ aluminum (ion)
Monoatomic anions to knowGroup # Charge on ion examples
VA -3 N3- nitride (ion)
P3- phosphide (ion)
VIA -2 O2- oxide (ion)
S2- sulfide
VIIA -1 F1- fluoride (ion)
Cl1- chloride (ion)
Br1- bromide (ion)
I1- iodide (ion)
Practice
• Name chemical formula
• Chemical formula name