Intro to Chemistry

Atomic Structure Nucleus- center of an atom

-contains protons

(which are positive)

-contains neutrons (which are neutral)

Ex- Sodium:

Bohr Model of Atom

Atomic Structure

Outside the Nucleus: Electrons (which are negative) surround the nucleus in energy levels

1st energy level = holds 2e

2nd energy level = holds 8e

3rd energy level = SAVE

4th energy level = FOR CHEMISTRY!!

Subatomic Particles Organized

Charge Location Mass

Protons

Neutrons

Electrons

Subatomic Particle Organized

Charge Location Mass

Protons Positive In nucleus 1 amu

Neutrons Neutral In nucleus 1 amu

Electrons Negative Outside of nucleus/ in energy levels

0 amu

Atomic Mass

An atom is defined by the number of PROTONS IT HAS!!!

Chemistry tidbits Chemical Symbol- letter representing the atom (sometimes from

Latin)

Chemistry tidbits Atomic number = number of protons

Mass number = # protons + # neutrons

Don’t bother to weigh the air inside the box

So how can you calculate NEUTRONS??

Calculating Neutrons is a simple algebraic problem…

Mass Number = protons + neutrons

Atomic Number = protons

Write the equation…

Mass Number= Atomic Number + neutrons

#Neutrons = (mass number – atomic number)

Chemistry tidbits Usually can assume:

# protons = # electrons

ONLY true for NEUTRAL ATOMS!

And remember…

Don’t mess with the

PROTONS!!!

So what CAN we “mess with?”

Neutrons…

Changes the MASS

Get an ISOTOPE

Electrons…

Changes the CHARGE

Get an ION

Atomic Mass Mystery…

Look at the atomic mass for Oxygen. What does it say (exactly?)

15.9999

What is the atomic mass?

P + N

So what the heck!?!?!

Average of the actual isotopes on Earth!!!

Isotopes

Isotopes are different atoms of the same element that contain the same number of protons but different number of neutrons.

Examples Cl-35 vs. Cl-37

17P 17P

18N 20N

How to write isotopes…

Mass/Hyphen Notation:

Especially important for a form of the isotope that is NOT the “usual”

Write the symbol, a dash, and the mass # for that isotope

Ex’s

C-14

C-12

How to write isotopes…

Nuclear Symbol Notation

Includes the symbol, atomic #, and the mass # for that isotope

Ex’s

14

6

C

What else CAN we “mess with?”

Neutrons…

Get an ISOTOPE

Electrons…

Get an ION

Periodic Table tidbits

Period table organization – organized by increasing atomic number

Split into metals (left side of stair step line) and nonmetals (right side of stair step line)

Metalloids- surround the stairstep line

Groups (families) – vertical columns (#1-18)

Periods – horizontal rows (#1-7)

Intro to Periodic Table

Periodic Table tidbits Period table organization – organized by increasing atomic number

Split into metals (left side of stair step line) and nonmetals (right side of stair step line)

ONE EXCEPTION

Hydrogen!

vertical columns (#1-18)

Groups

horizontal rows (#1-7)

Periods

Metals-left side of table

Exist as solids at room temperature

Shiny

Good conductors of heat & electricity

Malleable (can be bent)

Nonmetals-right side of table

Most are gases at room temperature

Some are brittle solids- carbon, sulfur, iodine, & phosphorus

Most do not conduct heat & electricity well

Metalloids- next to zigzag line b/w metals & nonmetals Properties fall between neighbors on both sides

Most are silvery in appearance, brittle, poor conductors of heat & electricty

Transition Metals

Metals- which are less reactive than the alkali or alkaline earth metals

Often exist as oxide or sulfide ores

ex. Iron sulfide or iron oxide

You’ll learn more in chemistry about these elements

Major Groups on periodic table

Alkali metals- group 1- most reactive Alkaline earth metals- group 2 Transition metals- groups 3-12 Metalloids- surround stairstep line Halogens- group 17 Noble gases-group 18 (inert gases-stable; nonreactive) Periodic table

Lewis Dot Structures

Lewis dot diagrams- display the number of valence electrons (outermost electrons) around the element symbol

Used to show how atoms of different elements bond and form compounds

Hint- use group number to find valence electrons

Electron configurations