Chapter 4 Atoms and the Periodic Table Design of the Periodic Table.
Chapter 5 The Periodic Table
description
Transcript of Chapter 5 The Periodic Table
Chapter 5The Periodic Table
Key Concepts:· Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.· The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.
5.1 Organizing the Elements:
Why is the Periodic Table important to me?
The periodic table is the most useful tool in chemistry.
You get to use it on quizzes and tests!
It organizes lots of information about all the known elements.
Pre-Periodic Table Chemistry …
…was a mess!!!No organization of
elements.Imagine going to a grocery
store with no organization!!Difficult to find information.Chemistry didn’t make
sense.
Previous attempts to organize known elements failed to work for all known elements at the time
Russian Chemist and teacher, Dmitri Mendeleev, discovered a way
Found a way to approach the problem when playing his favorite card game, a version of solitaire (organization was the key)
Solitaire…??????
Dmitri Mendeleev: Father of the Table
How does the game of solitaire work???
HOW HIS WORKED…Put elements in rows by increasing atomic
weight.Elements with similar properties were in the
same column.Put elements in columns by the way they
reacted.
Dmitri Mendeleev: Father of the Table
Periodic Table: an arrangement of elements in columns, based on a set of properties that repeat from row to row
Mendeleev’s Periodic Table
Table was not complete, not all elements had yet been discovered
He left gaps/spaces in his table for those elementsHe was NOT the first to organize the elements in
the form of a tableHe was the FIRST to offer good explanations for
how the properties of an element were related to its location in his table
He used the gaps in his tables to predict properties of undiscovered elements
Other scientists used the predictions to help in their search for undiscovered elements
Mendeleev’s Prediction
The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be
With the periodic table, chemists could do more than predict the properties of new elements – they could explain the chemical behavior of different groups of elements!!!
Evidence Supporting Mendeleev’s Table
5.2 The Modern Periodic Table
Mendeleev wasn’t too far off.Now the elements are put in rows by
increasing ATOMIC NUMBER!!
The horizontal rows are called periods and are labeled from 1 to 7.
The vertical columns are called groups are labeled from 1 to 18.
The Current Periodic Table
Period: A row in a periodic table of elements (left to right)
To understand the structure of the table, think what happens as the atomic number increases: Reminder: Atomic Number = Number of Protons
First energy level has ONLY 1 orbitalThe 1 e- in a hydrogen atom and 2 e- in a
helium atom can fit in this orbital (first energy level)
This is why H and He are in Period 1
PERIODS
Lithium, 1st element in Period 2, has one of its the three electrons in the second energy level This is why lithium is the first element in
Period 2Sodium, 1st element in Period 3, has one e- in
its third energy levelPotassium, 1st element in Period 4, has 1 e- in
its fourth energy levelThis pattern applies to ALL the elements in
the 1st column on the table
PERIODS
Families (groups) on the Periodic Table
Columns are also grouped into families (or groups).
Families may be one column, or several columns put together.
Families have names (Just like your family has a common last name.)
Group: A column in a periodic table of elements
Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups
Groups
Periodic Law: the pattern of repeating properties displayed by elements in the periodic table
Elements within a group have similar properties: Similar e- configurations (see example
above – first column of the table) Electron configuration determines an
elements chemical properties
Groups
Various Trends of the Periodic Table
Atomic mass is a value that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes.
Atomic Mass
Mass of an atom in grams is EXTREMELY small
Scientists came up with an easier way to talk about mass Chose one isotope to serve as a standardScientists assigned 12 atomic mass units
(amu’s) to the carbon-12 atom (which has 6P and 6N)
Atomic Mass Unit (amu): 1/12 the mass of a carbon-12 atom
Atomic Mass Units
Chlorine has an atomic number of 17 and an atomic mass of 35.453 atomic mass units
Where does the number 35.453 come from??? There are two natural isotopes of Chlorine:
Chlorine-35 which has 17 protons and 18 neutrons
Chlorine-37 which has 17 protons and 20 neutrons
An Example…Isotopes of Chlorine
Atomic masses come from an average of the isotopes for a given element that exist in nature
The value for atomic mass is known as a “weighted average”
Cl-35 occurs 3 times as often as Cl-37
Take an average of those numbers: (3 × 35) + (1 × 37) ----------------------------- = 35.453 4
It’s a weighted average of the isotopes
Elements are classified as metals, nonmetals, and metalloids.
Classes of Elements
Metals
Metals: elements that are good conductors of electric current and heat.
Properties of Metals:Except for mercury, metals are solid at room
temperatureMost metals are malleableMany metals are ductile (can be drawn into thin
wires)Some metals are extremely reactive* (page
135, figure 10)*Meaning they easily combine chemically with
other elements
Metals
Transition Metals: metals in groups 3-12, form a bridge between the elements on the left and right sides of the tables. Examples: copper and silverSome of the first elements discovered Ability to form compounds with distinctive
colors (page 137 production of colored glass)
Includes the lanthanide and actinide series (at the bottom of the table)
Transition Metals
Nonmetals
Nonmetals: elements that are poor conductors of heat and electric current Properties opposite those of metals
Low boiling pointsMost are gases at room temperatureNonmetals that are solid at room
temperature tend to be brittle (will shatter)Some very reactive, some not at all, some
fall somewhere in betweenFluorine (in Group 17) is the most reactive
nonmetal (found in toothpaste)
Nonmetals
Metalloids
Metalloids: elements with properties that fall between those of metals and nonmetals Ability to conduct electric current varies
with temperature Pure silicon (Si) and germanium (Ge) are
good insulators at low temperatures and good conductors at high temps.
Metalloids
Across a period from left to right, the elements become less metallic and more nonmetallic in their properties Most reactive metals on left side Most reactive nonmetals on the right side (in
Group 17) Period 3 elements (left to right) provide an
example of this (page 138, Figure 13)
Variation Across a Period
5.3 Representative Groups
Why is hydrogen (H) on the left side of the table with the active metals?
Hydrogen’s location is related to its electron configuration, not its properties!!!
Hydrogen…
Wonder why there are 2 numbering schemes on the periodic table?When the ‘A’ groups are numbered 1-8, they
provide a reminder about the electron configurations of the elements in those groups
The number of an ‘A’ group matches the number of valance electrons in an electron configuration for an element in that group
Patterns of Electron Configuration
Valence Electron: an electron that is in the highest occupied energy level of an atomValence electrons play a key role in chemical
reactionsProperties vary across a period because the
number of valence electrons increases from left to right
Elements in a group have similar properties because they have the same number of valence electron
Hydrogen is on far left of table because it has one valence electron, just like the rest of the elements in that column
Valence Electrons
Valence Electrons
Valence Electrons Lewis Structure
Hydrogen- YellowHydrogen belongs to
a family of its own.Hydrogen is a
diatomic, reactive gas.
Hydrogen was involved in the explosion of the Hindenberg.
http://www.youtube.com/watch?v=F54rqDh2mWA
Hydrogen is promising as an alternative fuel source for automobiles.
Alkali Metals- Lt. Blue1st column on the periodic table
(Group 1 /1A) not including hydrogen.
Very reactive metals, always combined with something else in nature (like in salt).
Single valence electronSoft enough to cut with a butter knife.The reactivity of alkali metals increases
from the top of Group 1A to the bottomLithium (Li) down through Francium (Fr)
http://www.youtube.com/watch?v=m55kgyApYrY
Alkali Metals
Alkaline Earth Metals- BrownGroup 2 / 2A on the periodic
table. Reactive metals that are
always combined with nonmetals in nature.
Several of these elements are important mineral nutrients (such as Mg and Ca).
2 valence electronsHarder than metals in Group 1AHigher melting point than Group 1ADifferences in reactivity among the
alkaline earth metals are shown by the ways they react with waterCalcium, strontium, and barium react easily
with cold waterMagnesium reacts with hot waterNo change with beryllium and water
Alkaline Earth Metals
Transition Metals- WhiteElements in
groups 3-12Less reactive,
harder metals.Includes metals
used in jewelry and construction.
Most are hard and shiny.
Transition Metals- White
Boron Family- Light GreenElements in group 13 (3A)Aluminum:
Metal was once rare and expensive, not a “disposable metal.”
Most abundant metal in Earth’s crust
Less reactive than sodium and magnesium
strong, lightweight, malleable, and good conductor of electric current
3 valence electronsBoron is used in
glassware like flasks because it doesn’t shatter when it undergoes a rapid temperature change
Boron Family
Carbon Family- RedElements in group 14 (4A)Group 4A contains one nonmetal (C), 2
metalloids (Si, Ge), and 2 metals (Sn, Pb)
Contains elements important to life and computers.
Carbon is the basis for an entire branch of chemistry.
Coal and oil are mostly made of carbon.
4 valence electronsMetallic nature increases from top to
bottom (Ge is better conductor than Si)Life would not exist without carbon (except
for water, most of the compounds in your body contain carbon)
Reactions in your body controlled by carbon compounds
Si is 2nd most abundant element in Earth’s crust (found in rocks, sand, and glass)
Carbon Family
Nitrogen Family- Dark BlueElements in group 15 (5A)Nitrogen makes up over ¾ of
the atmosphere.Nitrogen and phosphorus are
both important in living things.
The red stuff on the tip of matches is phosphorus.
5 valence electrons2 nonmetals, 2
metalloids, and 1 metal
Contain a wide range of physical properties
Nitrogen Family
Oxygen Family- OrangeElements in group 16 (6A)Oxygen is necessary for
respiration.Many things that stink, contain
sulfur (rotten eggs, garlic, skunks, etc.)
6 valence electrons3 nonmetals and 2 metalloidsOxygen is most abundant element in
Earth’s crust
Oxygen Family
The 10 most abundant elements by mass in the earth's crust . All are main-group elements except iron and titanium.
Halogens- PurpleElements in group 17 (7A)Very reactive, volatile, diatomic,
nonmetalsAlways found combined with
other element in nature .Used as disinfectants and to
strengthen teeth.
7 valence electronsDespite physical differences, the halogens
have similar chemical propertiesHighly reactive nonmetals, with fluorine being
the most reactive and chlorine a close 2nd
React easily with most metalsChlorine added to drinking water and
swimming pools to kill bacteria
The Halogens
The Noble Gases- Dark GreenElements in group 18
(8A)VERY unreactive,
monatomic gasesUsed in blimps to fix the
Hindenberg problem.Have a full valence
shell.
8 valence electronsEXCEPTION is Helium, it has 2 valence
electronsColorless and odorlessUsed in lighted “neon” signs
The Noble Gases