Chapter 3 - Atoms

Democritus

Argued that if you cut a substance in half, what results is two pieces of the same substance and that, eventually, you would reach a point where you could no longer divide it and still have the same substance.

Antoine Lavoisier

Created the Law of Conservation of Mass

Law of Conservation of Mass

In chemical reactions, matter is neither created or destroyed.

John Dalton

Created the Modern Atomic Theory

Unchanged Atomic Theory

\-Elements are made of tiny, indivisible particles called atoms

\-The atoms of each element are unique

\-Atoms can join together in whole number ratios to form compounds

\-Atoms are unchanged in chemical reactions

Three Foundational Ideas of Chemistry

1. All matter is composed of atoms
2. The atoms of each element have unique characteristics and properties


1. In chemical reactions, atoms are not changed, but combine in whole - number ratios to form compounds

How are we able to visualize atoms on a metal surface?

Through scanning tunneling microscopy

How can we visualize the arrangement of atoms?

X - Ray Crystallography

How does X - Ray Crystallography work?

A solid is bombarded with X - Rays, and based on the patterns the X - Rays form as they pass through the material, and scientists are able to visualize the arrangement of atoms in the solid

Dmitri Mendeleev

Father of the Periodic Table

The periodic table has rows that are called periods, and columns that have _____ _____, and they are called groups or families

Similar properties

The blocks of elements on the left and right sides of the periodic table are the _____________

Main group elements

The elements in the middle block are called the _________

Transition elements

At the bottom of the periodic table are two additional rows, called the ___________________

inner transition elements

On the left hand side of the periodic table, usually solid at room temperature, can be molded into different shapes, and they conduct heat and electricity

Metals

In the columns 2 - 13 and are harder and less reactive than the metals of the columns 1 - 2

Transition Elements

Has heavier, naturally occurring metals called rare earth metals

The first row of the inner transition metals, lanthanide series

The first few are mostly man made, although trace amounts have been found in nature

The second row of the inner transition metals, the actinide series

The primary atomic building blocks for all plant and animal life; are found on the upper - right side of the periodic

Nonmetals

Has a stair step pattern between the metals and nonmetals, they conduct electricity but not as efficiently as metals do (semi conductors) and are essentially the components of modern electronics

Metalloids

Group 1A: Alkaline Metals

Soft metals that react violently with water or even with moisture in the air

Group 2A: Alkaline Earth Metals

Less reactive than group 1A and burn brightly when combined with oxygen

Group 7A: Halogens

Have diatomic molecules in elemental form and form many different compounds that make substances such as bleach, Teflon, fire retardants, antiseptics, and table salt

Group 8A: Noble Gases

Generally do not form compounds because they do not react with other elements and are gases at room temperature.

Which part of Dalton’s Atomic Theory turned out to not be true?

Atoms could not be broken into smaller peices

Subatomic particles

Small components that make up atoms

What properties do we use to make up atoms and subatomic particles?

Their mass and their charge

What is electricity and electrical energy?

A form of energy that involves the motion of charged particles

Alessandro Volta

Built the first electrochemical cell (battery)

What was the result of Volta’s device?

An electrical current, the flow of charged particles from one side of the battery to another

Using this controlled electrical energy of the battery, scientists later discovered that you can use electrical energy to

separate some compounds, such as water, into their elements and to discover elements in a few short years

Plum Pudding Model

Created by Thomson and other scientists; small, negative electrons were spread throughout the muffin

Alpha Particles

Positively charged particles

Rutherford knew that the Plum Pudding Model was incorrect when

some of the alpha particles reflected off of the film and back toward the alpha particle source, instead of passing straight through

What was Rutherford’s conclusion?

Most of the atom was empty space, with a very dense nucleus at the center of each atom

Although the nucleus contains almost all of the mass of the atom, it is ______________

incredibly dense, packing the mass into a very tiny volume

Atomic number

integer value normally seen above the atomic symbol of the periodic table and also tells us the number of electrons in the neutral atom

Mass number

the sum of the number of protons and the number of neutrons in an atom

Isotopes

Atoms that have the same atomic number, but a different mass number

If we want to show the atomic number, we place the atomic numbers at the ______________________

lower left - hand side of the atomic symbol

If we want to show the atomic mass of an atom, we plan the atomic mass number at the ______________

upper left - hand side of the atomic symbol

The mass number on the periodic table is the ____________

average mass number

Average atomic mass

A weight average of the different isotopes of an element

What is the equation for the average atomic mass?

Bohr Model

Electrons orbit the nucleus like planets orbit the sun

Quantum Model

Electrons behave as both particles and as waves

Atoms gain or lose electrons to form

ions