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Regents Chemistry
Agenda Monday 10/25/04Return all papersReview pg. 119 – 120 HW assignmentReview HW assignment from last ThursdayOutline for Notebook for Periodic Table
UnitTomorrow: Summary review of PT
Summary of PTMendeleev arranged the first Periodic Table according to atomic mass
But, we now arrange the table by increasing Atomic Mass
Arrangement
The periodic table is arranged according to Groups (families) in columns and Periods in rows
Elements of the same group have similar chemical properties because they have the same number of valence electrons
Groups (Families)
Some groups are named:
Group 1 : Alkali Metals
Group 2 : Alkaline Earth metals
Group 17 : Halogens
Group 18 : Noble Gases
Practice Problem
Which of the following elements have similar chemical properties
Which of the following is an Alkaline Earth Metal?
a) Na c) Lib) Ne d) F
a) Li c) Arb) Mg d) Cu
Key to TableAtomic Number - # of protons in an atom of an element: defines an element!
Atomic Mass - # of protons + Neutrons
Oxidation States - #s in upper right hand corner that describe how an atom behaves when it is in a bond
C12
6
-4
Practice
What element has 10 protons?
How do you determine how many neutrons are in an atom?
Neon
Atomic Mass – Atomic Number = # of protons
Average Atomic Mass
The Atomic mass number on the periodic table is actually the average of all known isotopes
We can fins this by multiplying the mass number of each element x it’s percent abundance and then adding them up
Practice
Find the Average Atomic Mass of the following:
Isotopes
In an electrically neutral atom, the number of protons equals the number of electrons
Positive protons + negative electrons
= 0 overall charge
But two atoms of the same element can have a different # of neutrons…
Isotopes
Atoms of the same element that have a different # of neutronsCarbon – 12 and Carbon – 14
But remember they have the same # of protons!
C C12 14
6 6
Practice Problems
Which of the following are isotopes of each other?
How many neutrons are in the following?Lithium – 8Sodium - 23
a) Nitrogen – 13 c) Carbon – 12b) Oxygen – 15 d) Nitrogen - 14
Divisions
Periodic Table is divided into Metals, Metalloids and nonmetalsMetals: are most of the elements of the table : are lustrous, malleable, ductile and good conductors of electricityNonmetals: on the right side of the staircase : are dull, brittle, poor conductorsMetalloids: on the staircase : Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium
Practice Problem
Which of the following is a good conductor of electricity?
Which of the following is a Noble Gas?
a) F c) Cub) Ar d) C
a) Ca c) Feb) Ne d) B
Natural State of Elements
Elements can be found: Monoatomic: one atom alone Diatomic: two atoms of the same element together
Most elements are found combined with other elements as compounds in nature
Most are solids, some are gases, bromine and mercury are the only liquids
Most reactive elements are in groups 1, 17, 18
Practice Problems
Which of the following is naturally a diatomic gas?
Which of the following is a liquid at room temperature?
a) Argon c) Copperb) Neon d) Oxygen
a) Helium c) Bromineb) Hydrogen d) Mercury
Trends on the Table
Ionization Energy – increases from left to right and up the columns
Atomic Radii – increases from right to left and down columns
Ionic Radii – depends on if the atom looses or gains electrons
Electronegativity – increases from left to right and up the columns
Reactivity – Groups 1,2 and 17 along with oxygen are most reactive
Trends
Electronegativity and ionization energy
Electronegativity and ionization energy
Ato
mic
Rad
ius
Atomic Radius
Practice Problems
Which of the following is the most electronegative?
Which of the following has the smallest atomic radius?
a) Li c) Nb) C d) O
a) Be c) Mgb) Ca d) Sr END
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