Post on 02-Jun-2018
transcript
8/11/2019 Atom, Molecule, Ion and Periodic Table
1/50
Atoms, Molecules and Ions
8/11/2019 Atom, Molecule, Ion and Periodic Table
2/50
ATOMS
8/11/2019 Atom, Molecule, Ion and Periodic Table
3/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
4/50
Daltons Atomic Theory (1808)
1. Each element is made up of tiny particles called atoms.
2. All atomsof a given element are identical, having the
same size, mass and chemical properties. The atoms of
one element are different from the atoms of all other
elements.
3. Compounds are formed when atoms of different
elements combine with each other. A given compound
always has same relative numbers and types of atoms.
4. A chemical react ioninvolves reorganization of theatoms-changes in the way they are bound together. The
atoms themselves are not changes in a chemical
reactions.
8/11/2019 Atom, Molecule, Ion and Periodic Table
5/50
2.1
Daltons Atomic Theory
8/11/2019 Atom, Molecule, Ion and Periodic Table
6/50
8 X2Y16 X 8 Y+
8/11/2019 Atom, Molecule, Ion and Periodic Table
7/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
8/50
Cathode Ray Tube
8/11/2019 Atom, Molecule, Ion and Periodic Table
9/50
Cathode Ray Tube
8/11/2019 Atom, Molecule, Ion and Periodic Table
10/50
Thompsons Model of Atom
(Plum Pudding Model)
Spherical cloud of
positive charge
electron
8/11/2019 Atom, Molecule, Ion and Periodic Table
11/50
1. atoms positive charge is concentrated in the nucleus
2. proton (p) has opposite (+) charge of electron (-)
particle velocity ~ 1.4 x 107m/s
(~5% speed of light)
(1908 Nobel Prize in Chemistry)
8/11/2019 Atom, Molecule, Ion and Periodic Table
12/50
(a)
(b)
(a) The expected results of the metal foil experiment if Thompsons model
were correct
(b) Actual results
8/11/2019 Atom, Molecule, Ion and Periodic Table
13/50
e-charge = -1.60 x 10-19C
Thomsons charge/mass of e-= -1.76 x 108C/g
e-
mass = 9.10 x 10-28
g
Measured mass of e-
(1923 Nobel Prize in Physics)
8/11/2019 Atom, Molecule, Ion and Periodic Table
14/50
mass p = mass n = 1840 x mass e-
Protons and electrons are the only particles that have a charge.
Protons and neutrons have essentially the same mass.
The mass of an electron is so small we ignore it.
8/11/2019 Atom, Molecule, Ion and Periodic Table
15/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
16/50
Atomic number(Z) = number of protons or electrons
Mass number(A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopesare atoms of the same element (X) with different
numbers of neutrons in their nuclei
XAZ
H11 H (D)
21 H (T)
31
U
235
92 U
238
92
Mass Number
Atomic NumberElement Symbol
Atomic number, Mass number and Isotopes
8/11/2019 Atom, Molecule, Ion and Periodic Table
17/50
6 protons, 8 (14 - 6) neutrons, 6 electrons
6 protons, 5 (11 - 6) neutrons, 6 electrons
Do You Understand Isotopes?
How many protons, neutrons, and electrons are in C14
6 ?
How many protons, neutrons, and electrons are in C11
6 ?
8/11/2019 Atom, Molecule, Ion and Periodic Table
18/50
PERIODIC TABLE
8/11/2019 Atom, Molecule, Ion and Periodic Table
19/50
PERIODIC TABLE
A systematic catalog of
elements.
Elements are arranged in
order of atomic number. The rows on the periodic
chart are periods.
Columns are groups.
Elements in the same grouphave similar chemical
properties.
8/11/2019 Atom, Molecule, Ion and Periodic Table
20/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
21/50
Groups
These five groups are commonly referred to by
these names
8/11/2019 Atom, Molecule, Ion and Periodic Table
22/50
Period
Group
AlkaliMetal
NobleG
as
Halo
gen
AlkaliEarth
Metal
Transition metals
8/11/2019 Atom, Molecule, Ion and Periodic Table
23/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
24/50
MOLECULE & ION
8/11/2019 Atom, Molecule, Ion and Periodic Table
25/50
A moleculeis an aggregate of two or more atoms in a
definite arrangement held together by chemical forces
H2
H2
O NH3
CH4
A diatom ic molecu lecontains only two atoms
H2, N2, O2, Br2, HCl, CO
A polyatom ic m olecu lecontains more than two atoms
O3, H2O, NH3, CH4
8/11/2019 Atom, Molecule, Ion and Periodic Table
26/50
Ions
When atoms lose or gain electrons, they become
ions.
Cations are positive and are formed by elements on the
left side of the periodic chart.
Anions are negative and are formed by elements on the
right side of the periodic chart.
8/11/2019 Atom, Molecule, Ion and Periodic Table
27/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
28/50
Ionic Bonds
Ionic compounds (such as NaCl) are generally
formed between metals and nonmetals.
8/11/2019 Atom, Molecule, Ion and Periodic Table
29/50
An ionis an atom, or group of atoms, that has a net
positive or negative charge.
cat ionion with a positive chargeIf a neutral atom losesone or more electrons
it becomes a cation.
anionion with a negative charge
If a neutral atom gainsone or more electronsit becomes an anion.
Na 11 protons11 electrons Na+ 11 protons10 electrons
Cl17 protons
17 electrons Cl-17 protons
18 electrons
2.5
8/11/2019 Atom, Molecule, Ion and Periodic Table
30/50
A monatom ic ioncontains only one atom
A polyatom ic ioncontains more than one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
OH-, CN-, NH4
+, NO3
-
8/11/2019 Atom, Molecule, Ion and Periodic Table
31/50
13 protons, 10 (133) electrons
34 protons, 36 (34 + 2) electrons
Do You Understand Ions?
How many protons and electrons are in ?Al2713
3+
How many protons and electrons are in ?Se7834
2-
8/11/2019 Atom, Molecule, Ion and Periodic Table
32/50
2.6
8/11/2019 Atom, Molecule, Ion and Periodic Table
33/50
A molecular formulashows the exact number of
atoms of each element in the smallest unit of a
substance
An empir ical formulashows the simplest
whole-number ratio of the atoms in a substance
H2OH2O
molecular empirical
C6H12O6 CH2O
O3 O
N2H4 NH2
8/11/2019 Atom, Molecule, Ion and Periodic Table
34/50
Structural formulas show the
order in which atoms arebonded.
Perspective drawings also show
the three-dimensional array of
atoms in a compound.
8/11/2019 Atom, Molecule, Ion and Periodic Table
35/50
i on ic compoundsconsist of a combination of cations
and an anions
the formula is always the same as the empirical formula the sum of the charges on the cation(s) and anion(s) in each
formula unit must equal zero
The ionic compound NaCl
8/11/2019 Atom, Molecule, Ion and Periodic Table
36/50
Writing Formulas
Because compounds are electrically neutral, one
can determine the formula of a compound thisway:
The charge on the cation becomes the subscript on the
anion.
The charge on the anion becomes the subscript on thecation.
If these subscripts are not in the lowest whole-number
ratio, divide them by the greatest common factor.
8/11/2019 Atom, Molecule, Ion and Periodic Table
37/50
Formula of Ionic Compounds
Al2O3
2 x +3 = +6 3 x -2 = -6
Al3+ O2-
CaBr2
1 x +2 = +2 2 x -1 = -2
Ca2+ Br-
Na2CO3
1 x +2 = +2 1 x -2 = -2
Na+ CO32-
8/11/2019 Atom, Molecule, Ion and Periodic Table
38/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
39/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
40/50
Chemical Nomenclature
Ionic Compounds often a metal + nonmetal
anion (nonmetal), add ide to element name
BaCl2 barium chloride
K2O potassium oxide
Mg(OH)2 magnesium hydroxide
KNO3 potassium nitrate
8/11/2019 Atom, Molecule, Ion and Periodic Table
41/50
Transition metal ionic compounds
indicate charge on metal with Roman numerals
FeCl2 2 Cl- -2 so Fe is +2 iron(II) chloride
FeCl3 3 Cl- -3 so Fe is +3 iron(III) chloride
Cr2S3 3 S-2-6 so Cr is +3 (6/2) chromium(III) sulfide
8/11/2019 Atom, Molecule, Ion and Periodic Table
42/50
Molecular compounds
nonmetals or nonmetals + metalloids
common names
H2O, NH3, CH4, C60
element further left in periodic table
is 1st
element closest to bottom of group is
1st
if more than one compound can be
formed from the same elements, use
prefixes to indicate number of each
kind of atom
last element ends in ide
8/11/2019 Atom, Molecule, Ion and Periodic Table
43/50
HI hydrogen iodide
NF3 nitrogen trifluoride
SO2 sulfur dioxide
N2Cl4 dinitrogen tetrachloride
NO2 nitrogen dioxide
N2O dinitrogen monoxide
Molecular Compounds
TOXIC!
LaughingGas
8/11/2019 Atom, Molecule, Ion and Periodic Table
44/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
45/50
An acidcan be defined as a substance that yields
hydrogen ions (H+) when dissolved in water.
HClPure substance, hydrogen chloride
Dissolved in water (H+Cl-), hydrochloric acid
An oxoacidis an acid that contains hydrogen,
oxygen, and another element.
HNO3 nitric acid
H2CO3 carbonic acid
H2SO4 sulfuric acid
HNO3
8/11/2019 Atom, Molecule, Ion and Periodic Table
46/50
8/11/2019 Atom, Molecule, Ion and Periodic Table
47/50
2.7
N l t f Bi
8/11/2019 Atom, Molecule, Ion and Periodic Table
48/50
Nomenclature of Binary
Compounds
The less electronegativeatom is usually listed first.
A prefix is used to denotethe number of atoms ofeach element in thecompound (mono- is notused on the first element
listed, however.)
N l t f Bi
8/11/2019 Atom, Molecule, Ion and Periodic Table
49/50
Nomenclature of Binary
Compounds
The ending on the more
electronegative element is
changed to -ide.
CO2: carbon dioxide
CCl4: carbon tetrachloride
8/11/2019 Atom, Molecule, Ion and Periodic Table
50/50
Nomenclature of Binary Compounds
If the prefix ends with aoroand the name of theelement begins with a
vowel, the two successivevowels are often elided intoone:
N2O5: dinitrogen pentoxide