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